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lIBRARY
Michigan State
University

This is to certify that the

thesis entitled

Ileal Starch Digestibility, Protein and Amino Acid Digest-
ibility, and Nitrogen Utilization of Nutrient—Dense Corn
Hybrids Fed to Growing Pigs.

presented by

Lara Lynn Andersen

has been accepted towards fulfillment
of the requirements for

 

 

Masters degree in Animal Science

 

Major professor

Date 09/0 i/Ol

0-7639 MS U is an Affirmative Action/Equal Opportunity Institution

 

 

PLACE IN RETURN BOX to remove this checkout from your record.
To AVOID FINES return on or before date due.
MAY BE RECALLED with earlier due date if requested.

 

DATE DUE DATE DUE DATE DUE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6/01 cJCIRC/DateDuepes-p. 15

ILEAL STARCH DIGESTIBILITY, PROTEIN AND AMINO ACID DIGESTIBILITY,
AND NITROGEN UTILIZATION OF NUTRIENT-DENSE CORN HYBRIDS FED TO
GROWING PIGS
By

Lara Lynn Andersen

A THESIS

Submitted to
Michigan State University
In partial fulfillment of the requirements
For the degree of

MASTERS OF SCIENCE
Department of Animal Science

2001

ABSTRACT
[LEAL STARCH DIGESTIBILITY, PROTEIN AND AMINO ACID DIGESTIBILITY,
AND NITROGEN UTILIZATION OF NUTRIENT-DENSE CORN HYBRIDS FED To
GROWING PIGS
By

Lara Lynn Andersen

Protein and starch quality of seven corns, high-oil (HO), high-oil paired
normal (HOPN), waxy (WX), waxy paired normal (WXPN), high-lysine (HL),
high-lysine paired normal (HLPN), and a normal yellow dent corn (NYD), were

. investigated in two experiments using growing pigs. Apparent and standardized
amino acid digestibilities between the corn hybrids were determined. A trend
existed, in which the hybrids, HO and HL, were lower (P S .10) in apparent and
standardized digestibility as compared to their respective paired normal hybrids,
HOPN and HLPN. Ileal starch digestibility was determined for two separate
years. For years 1 and 2, HO, WX, and HL corn hybrids were higher (P < .05) in
ileal starch digestibility as compared to YDPN. A positive, linear correlation (P <
.05) was found to exist between ileal starch digestibility and apparent protein, true
protein, and standardized ileal indispensable amino acid digestibility. The
objective of a third experiment was to determine nitrogen (N) metabolism in
growing pigs fed different corn hybrids. Nitrogen retained, N digestibility, and N
utilization was similar between all pre-planned comparisons: HO vs HOPN, HL

vs HLPN, WX vs WXPN, HO vs NYD, HL vs NYD, and WX vs NYD (P > .10).

 

I would like to dedicate this work to the one person who has been my true inspiration:
my mother, Diana. My mother has been a constant source of support and professional
advice throughout my life. She has been a tower of strength for her children and has

provided a stellar example of what I should strive to become as an adult.

iii

ACKNOWLEDGMENTS

I would like to thank Dr. Nathalie L. Trottier for believing in me and giving me the
opportunity to pursue my Master’s degree in swine nutrition. In addition, I would like to
thank the Michigan Corn Marketing board for their financial support for this research
project. I also thank Dr. Pao Ku for his endless hours of support that he provided me in
the lab during my time here at Michigan State University. Furthermore, I would like to
thank all of the fellow graduate students and staff of Michigan State University that
provided support and insight. Specifically, I want to thank Janet Snow, Emily Otto,
Juliana Perez-Laspiur, Pasha Lyvers, Xinfu Guan, Jeff Hill, Bob Burnett, Jane Link, Yun
Ying (Jackie), Dewey,»Longuski, and David Main. There are also several people that
deserve acknowledgments- for the support they-provided throughout this project: Dr. Hans
Stein, Dr. Kent Amos, Johnna Seaman, Donna Barnes, and Heather Nederveld. I also
thank the staff of the Michigan State University Swine Teaching and Research Facility;
especially, A1 Snedegar, Ray Kromer, Dwayne Simon, and Brian Story for providing
technical support both at the research metabolism unit and main farm. I also wish to
acknowledge my two best friends, Bridgitt Hency and Jennifer Jarzynka, for being so
understanding and supportive in every way possible. Finally, I cannot forget to thank my
parents, David Andersen and Diana Krueger, for their undying love and my fiance',

Timothy Worden, for his constant love and encouragement.

iv

 

TABLE OF CONTENTS

LIST OF TABLES ............................................................................................................ vii
LIST OF FIGURES ......................................................................................................... viii
INTRODUCTION ............................................................................................................... 1
LITERATURE REVIEW ........................... 2
Structure and nutrient composition of a standard corn kernel .......................................... 2
Waxy corn ......................................................................................................................... 5
High-oil corn ..................................................................................................................... 7
Opaque-2/ High-lysine corn ............................................................................................ 10
Starch: Digestion and utilization ..................................................................................... 14
Protein digestibility ......................................................................................................... 18
Conclusion ............................................................................................................ , ......... 24

CHAPTER 2: APPARENT AND STANDARDIZED ILEAL AMINO ACID
DIGESTIBILITIES OF VARIOUS NUTRIENT-DENSE CORN HYBRIDSS FED TO

GROWING PIGS ............................................................................................................... 25
Abstract .......................................................................................................................... 25
Introduction .................................................................................................................... 26
Materials and Methods ................................................................................................... 26
Results ............................................................................................................................ 31
Discussion ...................................................................................................................... 33
Implications .................................................................................................................... 36

CHAPTER 3: ILEAL STARCH, APPARENT PROTEIN, AND TRUE PROTEIN
DIGESTIBILITY VALUES FOR NUTRIENT-DENSE CORN HYBRIDS AND THE
RELATIONSHIP BETWEEN ILEAL STARCH AND THE FOLLOWING:
APPARENT PROTEIN, TRUE PROTEIN, AND STANDARDIZED INDISPENSABLE

AMINO ACID DIGESTIBILITY ..................................................................................... 49
Abstract .......................................................................................................................... 49
Introduction .................................................................................................................... 50
Materials and Methods ................................................................................................... 50
Results ............................................................................................................................ 53
Discussion ...................................................................................................................... 54
Implications .................................................................................................................... 58

CHAPTER 4: EFFECT OF NUTRIENT-DENSE CORN HYBRIDS FED TO

GROWING PIGS ON NITROGEN METABOLISM AND UTILIZATION .................. 81
Abstract .......................................................................................................................... 81
Introduction .................................................................................................................... 82
Materials and Methods ................................................................................................... 82

 

Results ............................................................................................................................ 84

Discussion ...................................................................................................................... 85
Implications .................................................................................................................... 87
SUMMARY AND GENERAL CONCLUSION .............................................................. 94
VITA ................................................................................................................................. 96
APPENDICES .................................................................................................................. 97
Appendix A .................................................................................................................... 98
Appendix B .................................................................................................................... 99
Appendix C .................................................................................................................. 100
Appendix D .................................................................................................................. 101
Appendix E .................................................................................................................. 102
LITERATURE CITED ................................................................................................... 104

vi

LIST OF TABLES

Table 1: Composition of experimental diets (as-fed basis, %) .......................................... 38
Table 2: Nutrient composition of corn hybrids (dry matter basis) ..................................... 39
Table 3: Amino acid concentration as a percent of total crude protein ............................. 40
Table 4: Amino acid top dress composition (g/kg) ............................................................ 41
Table 5: Lysine and feed intake of growing pigs fed corn hybrids ................................... 42

Table 6: Apparent indispensable amino acid digestibilities of the corn hybrids (%) ........ 43
Table 7: Apparent dispensable amino acid digestibilities of the corn hybrids (%) ........... 44

Table 8: Average values of the amount of endogenous AA losses determined at the
terminal ileum with a protein free diet (mg/kg DMI) ........................................................ 45

Table 9: Standardized indispensable amino acid digestibilities of the corn hybrids (%) ..46
Table 10: Standardizeddispensable amino acid digestibilities of the corn hybrids (%) ...47

Table 11: Standardized indispensable amino acid digestibilities of the corn hybrids (%) 48

Table 12: Apparent and true protein digestibilities of the corn hybrids (%) ..................... 60
Table 13: Ileal and fecal starch digestibilities of the corn hybrids (%) ............................. 61
Table 14: Composition of experimental diets (as-fed basis, %) ........................................ 89
Table 15: Nutrient composition of corn hybrids (dry matter basis) ................................... 90
Table 16: Amino acid top dress composition (g/kg) .......................................................... 91
Table 17: Nitrogen utilization and dry matter digestibility of corn hybrids ...................... 92

vii

LIST OF TABLES

Table 1: Composition of experimental diets (as—fed basis, %) .......................................... 38
Table 2: Nutrient composition of corn hybrids (dry matter basis) ..................................... 39
Table 3: Amino acid concentration as a percent of total crude protein ............................. 40
Table 4: Amino acid top dress composition (g/kg) ............................................................ 41
Table 5: Lysine and feed intake of growing pigs fed corn hybrids ................................... 42

Table 6: Apparent indispensable amino acid digestibilities of the corn hybrids (%) ........ 43
Table 7: Apparent dispensable amino acid digestibilities of the corn hybrids (%) ........... 44

Table 8: Average values of the amount of endogenous AA losses determined at the
terminal ileum with a protein free diet (mg/kg DMI) ........................................................ 45

Table 9: Standardized indispensable amino acid digestibilities of the corn hybrids (%) ..46
Table 10: Standardized dispensable amino acid digestibilities of the corn hybrids (%) ...47

Table 11: Standardized indispensable amino acid digestibilities of the corn hybrids (%) 48

Table 12: Apparent and true protein digestibilities of the corn hybrids (%) ..................... 60
Table 13: Ileal and fecal starch digestibilities of the com hybrids (%) ............................. 61
Table 14: Composition of experimental diets (as-fed basis, %) ........................................ 89
Table 15: Nutrient composition of corn hybrids (dry matter basis) ................................... 90
Table 16: Amino acid top dress composition (g/kg) .......................................................... 91
Table 17: Nitrogen utilization and dry matter digestibility of corn hybrids ...................... 92

viii

 

INTRODUCTION

Corn is the major cereal crop of the United States and the second most important
cereal grain worldwide. Corn typically provides adequate energy to growing pigs;
however, it is often deficient in protein. Recently, the use of “nutrient dense” corn
hybrids in swine diets has provided an alternative to feeding normal yellow dent corn
hybrids to growing pigs. However, little is known about the amino acid availability and
utilization of these genetically modified corns in growing pigs. Furthermore, research is
available for corn starch digestibility in young pigs; however, there is no data available
on the starch digestibility of various specialty corns in growing pigs. These questions are
addressed in the following chapters. The first and second chapters address the protein,
amino acid, and starch digestibility of the various corn hybrids. In addition, protein
utilization is addressed in the third chapter. We hypothesized that the protein and amino
acid digestibility and N utilization would be superior in the nutrient-dense hybrids as
compared to their respective paired normal corns. Furthermore, we hypothesized that
there was a positive, linear relationship between ileal starch digestibility and the
following: protein and amino acid digestibility. Thus, the present research provides some
insight as to what the benefits are, in terms of protein and starch digestibility, when
feeding high-oil, high-lysine, and waxy corn hybrids as a replacement for normal dent

corn hybrids in growing pigs.

 

Literature Review

Evidence of corn production has been traced as far back as 5000 B. C. (White, 1994).
Corn is thought to have originated in Mexico and other South American countries, where
the Mayan, Aztec, and Inca Indians had domesticated the crop and were using it for
human consumption. From there, corn production spread northward into the present day
Unites States and Canada.

Today, corn is the major cereal crop of the United States and the second most
important cereal grain worldwide. In the U. 8., corn production provides the number one
grain used in livestock feeds. Corn typically provides adequate energy for livestock;
however, it is often deficient in essential amino acids, vitamins, and minerals. Therefore,
researchers have spent many years developing corn hybrids with increased nutrient
concentrations that provide an advantage over the normal dent corn hybrids. Some
“specialty coms,” currently available due to advanced research and technology, are high-
oil, high-lysine (opaque-2), and waxy corns. These specialty corn hybrids have the
potential to provide a nutritional advantage to producers of growing pigs; however, little

information is available on their nutrient digestibility and utilization.

Structure and nutrient composition of a standard corn kernel

The mature corn kernel consists of six distinct parts: 1) the tip cap, 2) the hull (also
known as the pericarp), 3) the horny gluten part (floury endosperm), 4) the horny starch
part (homy or vitreous endosperm), 5) the white starch part (sofi starch), and 6) the germ
(Hopkins, 1974). Hopkins (1974) also stated that the horny gluten, the horny starch part,
and the white starch part comprise the endosperm of a conventional yellow dent corn

kernel.

 

Table 1. Percentage composition of each part of the corn kernel (% basis)‘

 

Kernel fraction % of kernel % Protein % Oil % Ash % Starch

 

Tip cap 1.40 6.90 1.80 1.30 88-90
Hull 5-6 4.25 .86 .90 90-94
Horny gluten 8-14 25 5 1.5 68-71
Horny starch 45 10 .21 .21 88-90
White starch 25 5-8 .29 .31 92
Germ 11 20 35 10 35

 

aAdapted from averaged data of corn ears of low, medium, and high protein content
(Hopkins, 1974).

The tip cap covers_the base or tip of the corn kernel, and provides protection to the end
of the germ. The hull is the very thin outer covering of the kernel. It consists largely of
carbohydrates, especially fiber. Together, the tip cap and the hull comprise only about 7.5
% of the weight of the kernel. The horny gluten portion of the kernel lies immediately
under the hull, and constitutes a second covering of the corn kernel. It comprises 8—14%
of the grain, and contains approximately 25% protein, making it the richest supply of
protein within the standard corn kernel. The horny starch part lies next to the horny
gluten and contains approximately 90% starch; yet, it also contains approximately 10%
protein. The white starchy part occupies the crown end of the kernel above the germ and
is also rich in starch content (92%). However, the white starchy part is low in protein (5-

8%). The germ occupies the center of the corn kernel toward the tip and extends about

 

one-half to two-thirds the length of the kernel. It comprises approximately 11% of the
kernel; however, this varies depending on the type of corn hybrid (more in high-oil corns

and less in low-oil corns) (Hopkins et al., 1974).

Corn kernel carbohydrates

The corn kernel is comprised of 70-75% starch (Boyer, 1994). The majority of the
starch (80-90%) is found within the endosperm (the horny gluten, the horny starch, and
white starch parts). Corn starch. exists as two distinct polymers: amylose and
amylopectin. Amylose is a linear starch polymer of a-1,4-linked glucose units (Boyer,
1994). In contrast, amylopectin is a branched-chain polymer which has elongated a-1,4-
linked glucose units, but also has a-l,6—linked branching points approximately every 20-

25 glucose units (Gray, 1992).

Corn kernel proteins

A portion of the protein in a standard yellow dent corn kernel is found in the horny
gluten (25%) and the germ (20%). The horny gluten and germ contain approximately 5%
globulins, 7% albumins, 25% glutelins, and 52% prolamins (Boyer, 1994). The
prolamins, which are the major protein class, are often referred to as the zein fraction. A

high percentage of total protein in corn is found in the zein fraction.

Corn kernel lipids

Hopkins (1974) and Boyer (1994) described the corn kernel as containing
approximately 4.4% oil, the majority of which is found within the germ (80-85%). The
horny gluten, the horny and white starch, the hull, and the tip cap, together, provide

approximately 7% oil (Hopkins, 1974). Triacylglycerides, which contain a mixture of

 

saturated and unsaturated fatty acids, are the major component of most com oils (Boyer,
1994). The majority of commercial corn oils contain high percentages of linoleic acid
(50%) and low concentrations of linolenic acid (1%). The other fatty acids commonly
found in commercial corn oils are: oleic (40%), palmitic (12%), and stearic (2%) acid

(Boyer, 1994).

Waxy corn

Waxy corn was discovered in Shanghai, China in 1908. The endosperm of this
Chinese variety of corn had a distinctly different texture and appearance than the
common dent corns grown in the United States (Hanson, 1946). The endosperm of this
corn variety was described as having a very dull and hard waxy-like appearance. In
addition, this endosperm trait is controlled by a single recessive gene on chromosome
nine and was thus designated the waxy gene (Fergason, 1994).

Until the early to mid 1930’s, waxy corn production in the United States was limited.
However, early research at the Iowa Agricultural Experiment Station revealed that the
amylopectin starch from waxy corn had similar properties to tapioca starch taken from
the roots of cassava plants (Shopmeyer et al., 1943). Therefore, due to difficulties of

importing tapioca starch from the Far East during World War 11, commercial production

of waxy corn was increased.

Production of waxy corn

The most common breeding program for waxy corn is the simple backcross method.
This method was established due to competition among private seed companies to

provide the most superior waxy hybrid as fast as possible. Yields for most waxy hybrids

 

have come within 5% or less of the yields for most normal dent hybrids. In addition,
waxy corn hybrids have higher test weights than their corresponding dent hybrids

(F ergason, 1994).

Utilization of waxy corn

According to Johnston (1991) the unique properties of waxy cornstarch can be
attributed to the fact that nearly 100% of the starch in waxy corn is amylopectin, while
standard dent corn varieties contain starch that is approximately 25% amylose and 75%
amylopectin. The majority of the commercially produced waxy corn is contracted out to
wet milling companies. Wet milling of corn grain is a process which involves the
separation of starch from other constituents, such as fiber, germ, protein, and other minor
materials (Fergason, 1994). Waxy starches are used in a variety of ways in the paper,
textile, and adhesive industries'ln additron. waxy starches are often used in the food
industry to improve the uniformity, stability, and texture of various food products
(Fergason, 1994).

As a result of its successful use in the textile and food industries, studies were
conducted to determine if waxy corn would provide any benefits when fed to livestock.
McDonald (1973) observed an increase of more than 20% in average daily gains (ADG)
when lambs were fed waxy corn relative to normal dent corns. In addition, McDonald
(1973) observed an increase in feed efficiency approaching 10% in finishing beef cattle
when fed waxy corn as compared with normal dent corns. However, when nursery pigs
were fed waxy corn, there was no difference in ADG, average daily feed intake (ADFI),
or feed conversion when compared to normal dent corn (Johnston, 1991). In a similar

trial, growing pigs consumed more waxy corn than normal dent corn, but once again

showed nosignificant difference in average daily gain or feed intake between the two
corns. However, when given a choice between waxy and normal dent corn, they
consumed 2.6 times more normal dent corn than waxy corn (Hanson, 1946). In another
study where growing-finishing pigs were fed three different types of corn hybrids
(opaque-2, waxy, and normal dent corn), waxy corn diets showed a trend toward lower
average daily gains; however, the differences were not significant (Sachtleben, 1975).
Also, dry matter intakes of growing pigs fed waxy corn based diets were depressed by as
much as 45%, but dry matter digestibilities were similar for all three corn hybrids
(Sachtleben, 1975). As a result of these earlier studies, waxy corn has never been
considered a good replacement for most normal dent corn hybrids in livestock feed. No
additional research has been conducted to evaluate fithher the nutritional value of waxy

corn for livestock.

High-oil corn

The breeding of corn for higher oil contents which is of historical interest was initiated
at the University of Illinois in 1896. In 1981, after greater than .80 generations of
selection and “backcross” breeding, the Illinois high oil corn had an oil concentration of
approximately 19% (Weber, 1983). However, the grain yields, ear size, and weights were
dramatically reduced when compared to conventional corn hybrids. Furthermore, grain
yields of modern high-oil hybrids generally decrease at oil levels greater than 8%

(Lambert, 1994).

 

-
‘4 .4-

Production and nutritional composition of high-oil corn

Today, new high-oil hybrids are being produced under the “top-cross” breeding
program. This method involves blending two types of hybrids, in which 3 % of the plants
are “pollinators”, while the remaining 97 % of the plants are a high performing “male-
sterile” commercial hybrid. The pollen from the pollinator transfers the high oil trait onto
the kernels of the male-sterile hybrids, resulting in a “top-cross” high-oil corn hybrid
(Lauer, 1995). As a result of this method, new high-oil corn hybrids have kernel oil
concentrations of approximately 6-8%, which is a 2-3% increase over most conventional
corn hybrids (Lambert, 1994). In addition, this production strategy results in grain yields,
ear size, and kernel weights similar to conventional normal yellow dent corn hybrids.

The corn germ consists of the scutellum and the embryo. The scutellum in most
normal dent corn hybrids makes up about 10-12% of the total kernel dry weight;
however, the scutellum contains 83-85% of the total oil in the corn kernel (Lambert,
1994). High-oil hybrids typically have a larger germ size, which is mostly scutellar tissue,
and thus contributes to the increased oil content.

The increased oil content of high-oil corn hybrids have several added benefits: 1)
high-oil corn has nutritional advantages for feeding because of a greater energy/unit of
feed; 2) protein concentrations are higher and protein quality is enhanced because of the
larger scutellum size compared to normal dent corn hybrids. Watson and Freeman (1975)
reported that there is an increase of approximately .38% in protein content with each 1%
increase in oil; 3) high-oil hybrids usually have a higher proportion of yellow pigments

(carotenoids and xanthophylls) which are beneficial in poultry diets (Lambert, 1994).

 

Utilization of high-oil corn

In poultry, Han and Parsons (1987) compared high-oil and normal corn diets for
laying hens and broiler chicks. Laying hens fed a high-oil corn diet containing 17%
protein, from 23 to 38 weeks of age, had a better egg to feed ratio, egg production, and
yield compared to laying hens fed a normal corn diet. In a second study, a comparison
using broiler chicks from 8 to 22 days post-hatch fed diets containing high-oil (6-13%
oil) versus normal corn (4.3% oil) showed that chicks fed the high-oil diet had superior
gain/feed ratios (Han et al.,'1987). In another study, Parsons et al. (1998) analyzed the
true digestibility of amino acids and bioavailability of lysine in three high-oil (59-95%
ether extract) corns and one conventional (4.3% ether extract) corn in cecectomized
roosters. True digestibility of most amino acids for two of the high-oil (6.6 and 9.5%)
corns were significantly higher than in conventional corn and the third high-oil (5.9%)
corn. In addition, the bioavailability of lysine for all three high-oil corns was equal to or
greater than that in conventional corn.

Several studies have also looked at the effects of feeding high-oil corn to pigs.
Nordstrom et al. (1972) showed that a significant reduction in feed/gain occurred in
growing pigs fed high-oil corn varieties when compared to pigs fed a normal corn diet.
The high oil corn varieties had higher percent dry matter, percent ether extract, and gross
energy (kcal/kg) than the normal corn. The high-oil varieties also contained more protein
and slightly more of the essential amino acids on a dry weight basis. However, when
calculated as a percent of protein, the amino acids and protein quality of the high-oil

varieties were equal to that of the normal corn.

 

Adeola et al. (1994) measured the growth performance and utilization of energy of
three high-oil ( 5.4-9.7% ether extract) corn varieties and a normal corn (4.2% ether
extract). The digestible and metabolizable energy content of the normal corn was
consistently lower than all three of the high-oil corns. In addition, pigs fed the high-oil
corn with 9.7% ether extract gained 9% more weight daily than pigs fed the diet
containing the normal corn. Also, there was an improvement in feed efficiency of 8-10%
in pigs fed the high-oil corns when compared to the normal corn. Therefore, the data
suggests that. high-oil corn is beneficial as a replacement for conventional corn in the

livestock industry.

Opaque-2/High-lysine corn

The existence of the opaque-2 gene has been known since 1935. Yet, it was not until
1963 that Mertz et al. (1964) determined that the opaque-2 mutant endosperm had a
different amino acid pattern. There were increases in amino acids such as tryptophan,
histidine, arginine, aspartic acid, glycine, and cystine, but less glutamic acid, alanine,
methionine, leucine, and tyrosine. Furthermore, the opaque-2 kernel contained 69% more
lysine than most standard dent corns. The major reason for the change in the amino acid
pattern in opaque-2 hybrids is attributed to a reduction in the ratio of zein (15.7%) to
glutelin (42.3%) based on total protein as well as an increase in the lysine content of the
acid and alcohol-soluble zein fractions (Mertz, 1964). Murphy and Dalby (1971) showed
that the opaque-2 gene actually suppresses the synthesis of the zein, especially during

early development of the endosperm, resulting in a lower zein fraction and a higher lysine

lO

 

and tryptophan content of opaque-2 corn at maturity. Most standard dent corns from

North America contain 41 - 52% zein and 17 — 28% glutelin (Mertz and Bates, 1964).

Production of Opaque-2/ High-lysine corn

The opaque-2 gene, using the backcross method, has been incorporated into parental
seed stocks to produce high-lysine corn hybrids (West and Kincer, 1985). Although these
hybrids have an amino acid composition that improves the nutritional quality of com,
their utilization in animal feeds is currently limited. Reasons for the lack of use of these
hybrids in the US. are lower agronomic performances, such as lower yields due to lower
endosperm size and reduced kernel weight, in comparison with normal dent corns. Also,
the soft chalky appearance of high-lysine kernel is undesirable to producers (Boyer,
1994). Other problems previously associated with high-lysine hybrids included increased
moisture content, higher incidence of ear rot, greater damage from insects, poor
germination, increased kernel breakage, and a thicker pericarp (Boyer, 1994). Finally, the
availability of relatively inexpensive protein supplements, primarily soybeanmeal, have

also limited the use of high-lysine hybrids in livestock feeds.

Utilization of Opaque-2/ High-lysine corn

The use of high-lysine hybrids as a nutritional supplement for malnourished children in
underdeveloped countries has been widely accepted. In 1980 Graham et al. tested the
digestibility of energy and protein of normal, opaque-2 and a sugary-2 opaque-2 hybrid,
both as a degerminated endosperm and as a whole kernel meal in eight convalescent

malnourished children from 10 to 25 months of age. The results showed that the energy

11

 

- provided to malnourished infants by feeding the opaque-2 (91.2%) endosperm meal was
greater than that provided by the normal corn (83.2%) and the sugary-2 opaque-2
(82.1%) endosperm meals. However, the normal corn (73.2%) whole kernel meal
provided greater energy than that provided by opaque—2 (68.6%) and sugary-2 opaque-2
(67.2%) whole kernel meals. Apparent absorption of nitrogen (N) from the three whole
kernel corn meals were not significantly different. Furthermore, apparent retention of N
from the normal whole kernel meal was lower than from the opaque-2 and sugary-2
opaque-2 meals, but not significantly so. In a similar study by Graham et al. (1989) the
digestibility and utilization of casein, high-lysine corn and normal corn was determined
in six recovering malnourished children of varying age from 7.9 to 18.5 months. Results
showed that. energy digestibility of high-lysine com (87%) was less than the casein diet
(94%), but greater than the normal corn diet (84%). Apparent N absorption from high-
lysine com (70%) and normal com (69%) were much lower than from casein (82%). In
addition, apparent retention of N from high-lysine com (34%) was less than fi'om casein
(41%) but greater than from normal com (22%). Thus, opaque-2/ high-lysine corn
provides an important nutritional advantage to malnourished children when compared
with normal corn in underdeveloped countries.

Several studies have also been conducted to determine the effects of feeding opaque-
2/ high-lysine corn to swine. The initial opaque-2 corn work with pigs was conducted by
Beeson and Picket of Purdue University (Maner, 1975). They showed that pigs between
13.8 and 25.7 kg grew 3.6 times faster on opaque-2 corn than on normal corn. Also, pigs
fed opaque-2 corn grew at a rate equal to that of pigs fed a diet of normal corn and

soybean meal that supplied the same amount of crude protein (11.6%). In addition,

12

finishing pigs, with an initial body weight of 59 kg, gained weight 50% faster when fed
opaque-2 corn based diets compared to pigs fed normal corn based diets and at about the
same rate as pigs fed normal corn and soybean meal based diets containing 13% protein.
Cromwell et al. (1967) conducted two experiments to determine whether the improved
performance of swine fed opaque-2 corn was due to its high lysine content alone. In the
first experiment, the diets tested were two basal diets consisting of approximately 97%
opaque-2 corn and normal corn, respectively. In addition, L-lysine HCl was added alone
and in combination with L-tryptophan, to raise the dietary lysine-and tryptophan levels to
that of the opaque-2 corn. In the second experiment, opaque-2 and normal corn in
conventional com-soybean meal diets were compared at 16, 14, and 11.8% protein.
Again, L-lysine HCl and L-tryptophan, singly or in combination, were added to all the
normal corn diets. In both experiments, pigs fed the opaque-2 corn gained significantly
faster and more efficiently than pigs fed the normal corn without lysine and tryptophan
supplementation. Compared with pigs fed the normal corn diets in both experiments, the
results showed no beneficial responses in gains and only a slight improvement in feed
efficiency by raising the lysine content of the normal corn diet to that of the opaque-2
diet; indicating that the beneficial effects of opaque-2 corn for the pig do not lie solely in
its higher lysine content. Pigs I responded more to tryptophan than to lysine
supplementation, suggesting that tryptophan was more limiting than lysine in normal corn
at low dietary protein levels. Thus, the data suggests that the improved response in pigs
fed opaque-2 corn is primarily due to its higher content of both lysine and tryptophan.
Asche et al. (1986) determined the effects of corn type, normal yellow dent corn and

high-lysine corn, on energy and N digestibility. The results showed that dry matter,

13

 

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energy and N digestibilities were not significantly different between corn types. Thus,
this indicates that energy and N digestibility of high-lysine corn in typical diets for
growing pigs are similar to those on normal yellow dent corn diets.

Burgoon et al. (1992) tested a low-protein, high-lysine corn diet in starter and grow-
finishing pigs and determined that high-lysine corn did not provide an adequate supply of
protein to starter pigs but was adequate for grow-finishing pigs. Therefore, even with the
agronomic problems often associated with the opaque-2/ high-lysine corns, the high

protein quality provides an important nutritional advantage to malnourished infants and

growing pigs.

Starch: Digestion and utilization

Starch is the major storage carbohydrate and the most common digestible
polysaccharide found in plants. Starch represents about 70-80% of most com grains, a
large percentage of many roots and tubers, and is a major component of many grain
legumes. Corn is the most common source of starch in the world. In the US,
approximately 95% of commercial starch is produced from corn. The pericarp of the corn
kernel, which encases the embryo or germ as well as the endosperm, contains most of the
starch. The typical corn endosperm is approximately 87% starch, which comprises 82%

of its total grain weight (White, 1994).

Starch molecule

Starch is a polymeric carbohydrate consisting of glucose units linked together through
or-I,4 and or-1,6 D-glucosidic bonds. Starch is stored in highly organized granules
enmeshed in a protein matrix as two major types of polymers, i.e., amylose and

amylopectin.

l4

 

V ['1

 

The average amylose molecule is essentially a linear polymer of or-l,4-linked D-
glucose units having a molecular weight of 100 kDa (~ 600 glucose units). The
proportion of amylose in starch ranges from 0 to 80%, depending upon the plant species;
however, normal cereal starches contain approximately 20 to 30% amylose (Rooney and
Pflugfelder, 1986).

Amylopectin is a much larger, branched polymer which is the most abundant
component of normal starches (Rooney and Pflugfelder, 1986). Amylopectin also contains
linear chains of or-l,4-linked D-glucose, but has or-l,6 branch points every 20-25 glucose
units. Amylopectin comprises 70-80% of most cereal grain starches and is the only starch
in waxy genotypes of corn, sorghum, barley, rice, and millet. In general, amylopectin’s
molecular weight is approximately 1000 kDa (~ 6000 glucose units).

The amylopectin, amylose and intermediate fraction molecules are packed tightly
within tiny water-inSoluble starch granules and" are held together by hydrogen bonding.
The starch granules are formed inside the cellular organelle called the amyloplast;
however, each species within the plant kingdom produces starch granules of different
sizes, shapes, and stability. Grain starches usually have smaller granules than root and
tuber starches, and their size distribution is usually very wide. Root and tuber starch
granules are much larger and of a narrower size distribution. Legumes generally have
granules of intermediate size, and their distribution falls between the grains and tubers

(Moran et al., 1982).

15

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Starch granule

Starch granules are pseudo-crystals that have organized (crystalline) and relatively
non-organized (amorphous) areas. These granules resist water entry and enzyme attack
(Rooney and Pflugfelder, 1986). Rooney and Pflugfelder (1986) stated that the
amylopectin comprises the crystalline region, and has a cluster-like structure, whereas the
amylose may be found in both crystalline and amorphous regions. The amorphous region
is rich in amylose and less dense than the crystalline areas. Water moves freely through
the amorphous region, and amylase attack on the granule occurs here. In addition, any
chemical modification of starches for industrial use primarily affects the amorphous

region.

Starch digestion in livestock

In most animals the vast majority of srarches are digested within the intestinal lumen
by or-amylase (amylase, also known as or-1,4 glucano-hydrolase), which converts starch
to maltose. Amylase randomly hydrolyzes or-1,4 glucosidic bonds within starch
molecules, generating maltose, and branched and linear dextrins (principally from
hydrolysis of amylopectin). A small amount of amylase is present in the saliva of some
species; however, amylase is synthesized in the pancreas and secreted via the pancreatic
duct into the duodenum of the small intestine. Salivary amylase and pancreatic amylases
are of critical importance in starch digestion in nonruminants (Rooney and Pflugfelder,
1986). In fowl, starch digestion is almost exclusively accomplished by pancreatic
amylase as there is no salivary amylase available (Moran et al., 1982). Although swine
have salivary amylase, pancreatic amylase digests the majority of the starch. In addition,

the pancreatic sources found in swine and fowl are very similar. In contrast, ruminants

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fed oats, barley, or wheat as whole or crushed grain, will ferment up to 90% of the starch
within the rumen (Orskov, 1986). Due to a slower rate of starch digestion in corn, up to
40% of corn starch can bypass the rumen and undergo fithher digestion within the
intestine (Orskov, 1986).

The digestibility of starch can be affected by several factors, including the structure of
the starch granule and(or) grain kernel, protein-starch interactions, amount of amylase
production and(or) secretion, pH levels within the small intestine and the rate of passage
in the gastrointestinal tract. In general, cereal starches are more easily digested than root
and tuber starches, while legume starches have intermediate digestibility (Rooney and
Pflugfelder, 1986). Digestibility of a starch is generally inversely proportional to amylose
content. For example, high-amylose corn has poor digestibility in both raw and cooked
forms, while waxy cereal starches are among the most digestible of all starches. In
addition, interactions with proteins from cereal grains, such as corn and sorghum, can
reduce the susceptibility of both native and processed starch to enzyme hydrolysis.

Cunningham (1959) studied the ability of baby pigs to digest carbohydrates prior to
weaning. Baby pigs at birth, 15, 24, and 25 days were starved for 16 hours, after which a
stomach tube was inserted. Raw cornstarch, soluble starch, maltose, and glucose were
injected into the gut via a stomach tube. Digestibility of glucose (98%) and maltose
(89%) at the large intestine was highest in 25 day-old pigs. Raw cornstarch digestibility
increased with age, but was still very inefficient (48%) at 25 days of age. No consistent
trend was observed for soluble starch digestibility at the end of the large intestine;

however, soluble starch was significantly higher than raw cornstarch digestibility values.

17

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Van der Poel et al. (1992) conducted a study in which grower pigs were fed diets
containing 30% raw or processed whole faba beans. The effects of treatment on apparent
ileal and fecal digestibility of starch were investigated. No difference was observed in
ileal starch digestibility between the raw (97.7%) and processed (98%) faba bean diets.
Furthermore, fecal starch digestibility was complete (99.9%) for both raw and processed
faba bean diets.

In another study, Walker et al. (1993) determined the effects of carbohydrate source
on starch digestibility in mature dogs. Diets consisting of 67% extruded grain (corn and
rice) and 33% meat-based were fed to eight dogs fitted with ileal T-cannulas. Initial
starch content of the diet was different for corn (47.8%) and rice (57.4%). The results
indicated that ileal starch digestion was similar between corn (99.4%) and rice (99.5%).
Fecal starch digestion was nearly complete for rice (99.9%) and corn (99.8%).

In a similar study conducted with growing pigs, Everts et al. (1996) determined the
ileal starch digestibility of cornstarch and native pea starch. Once again, ileal starch
digestibility was similar between cornstarch (98.3%) and native pea starch (97.5%). In
addition, starch digestibility at the end of the large intestine was nearly complete (99%)
for both cornstarch and native pea starch.

Thus, the four studies discussed above suggest that starch digestion is complete at the
terminal ileum with a very low level of starch digestion occurring in the large intestine,

and is unaffected by starch source.

Protein digestibility
Digestibility of amino acids (AA) can be measured by two different procedures.

Initially, the fecal collection procedure, developed by Kuiken and Lyman (1948), was

18

used to determine AA digestibility. Using this procedure, digestible AA values represent
the amount of AA in the feedstuff that disappear over the total digestive tract of the pig.
However, due to recent experiments, it is generally agreed that the ileal collection of
digesta from the terminal ileum is more accurate than the traditional fecal approach
(Sauer and Ozimek, 1986). This is due to the fact that estimates of nutrient digestibility in
the pig obtained by comparing the composition of fecal matter to feed are confounded by
digestive processes in the lower tract, particularly the microbial activity in the cecum and
large intestine (Easter and Tanksley, 1973). Thus, AA digestibilities obtained by the fecal
analysis method are, for most AA in feedstuffs, higher than those obtained by the ileal
digesta collection method. Therefore, depending on the AA and on the feedstuff,
digestibilities obtained by the fecal analysis method overestimate those obtained by the
ileal digesta collection method (Sauer et al., 1989). However, ileal digesta collected at the
terminal ileum is confounded by the presence of endogenous AA. Also, digestibility of
AA can be measured (by two different methods. Most of the ileal AA digestibility
coefficients are obtained with the direct method. Using this method, the test diet is
formulated in such a manner that the test feedstuff provides the sole source of protein;
therefore, the digestibility coefficients can be directly determined by the difference
between the amount of feedstuff ingested and the amount collected at the terminal ileum.
There are several techniques used to collect digesta fi'om pigs. The simple “T”-piece
cannula is the most commonly used cannulation technique in the US. and the
Netherlands. The “T” cannula is inserted into the terminal ileum about 5-10 cm anterior
of the ileocecal valve (Sauer et al., 1989). Digesta is collected from the cannula after the

pigs have been on the test diets for 5-10 days. The advantages of this technique are: 1) the

19

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surgery is relatively simple; 2) collections can be made over a long period of time; 3)
fecal sampling can also be undertaken; and 4) it is possible to utilize one set of pigs for a
number of collections. The disadvantages are: 1) leakage occurs around the base of the
cannula which causes discomfort to the pig; 2) considerable labor. and expertise are
required to minimize irritation from the leakage (Batterham, 1994); and 3) an indigestible
marker must be included in the test diet. Other problem associated with the “T” cannula
is the question of obtaining a “representative” sample of digesta and possible
shortcomings of the. indigestible markers (Sauer, 1989).

Due to the uncertainties associated with obtaining a representative sample and the
shortcomings of indigestible markers, pigs are often fitted with re-entrant cannulas. This
type of cannula is inserted into either the terminal ileum, or either side of the ileocecal
valve or posterior to it (Sauer et al., 1989). The advantage with this technique is that a
total collection of digesta is possible without feeding an indigestible marker. The major
disadvantage is that the small intestine is severed leading to possible blockage of the
cannula depending on what feedstuff is fed to the animal. The extent to which blockage
occurs increases with increasing particle size, crude fiber content, feed intake, and factors
that increase the viscosity of the digesta (Sauer et al., 1989).

Within the past decade, a technique called the “ileal-rectal shunt” has become popular.
With this technique the terminal ileum is anastomosed to the rectum, thereby allowing
the digesta to bypass the large intestine and be collected from the anus. However, since
the large intestine is by-passed it is necessary to compensate the pig for mineral losses
(Sauer et al., 1989). The advantages of this technique are that it allows for complete

collection of digesta over the growth span of the pig and that it is also suitable for routine

20

collections. The disadvantages of this technique are that substantial surgery is involved
and that the technique is possibly unacceptable in many areas of animal ethics. Collection
is often messy, due to the fact that the pig has little control over rectal function. There is
also the question of whether the pig is functioning in a normal physiological manner.

The choice of technique may affect the calculated digestibility coefficients. For
example, with the re-entrant cannulas, feeding high-fiber diets and diets of increased
particle size often causes blockage, which ultimately affects the complete collection of
endogenous losses. (Sauer, 1989). This effect has not been observed with the “T” cannula

or the. “ileal-rectal shunt.”

Apparent digestibility

Apparent digestibility measures the difference between the AA intake and AA
excreted in the digesta, divided by the AA intake. The main disadvantage of measuring
apparent digestibility is that it underestimates the actual digestibility of a feedstuff by not
adjusting for endogenous nitrogen (N) or AA losses. In addition, apparent digestibility
coefficients are dependent on the crude protein/AA levels in the test diet. Thus, apparent
ileal AA digestibility coefficients increase curvilinearly with increasing AA levels in the

diet (Furuya and Kaji, 1989).

Methods used to determine endogenous losses
Endogenous secretions are proteins or AA that originate from various regions within
the body, including saliva, gastric juices, bile acids, intestinal juices, sloughed off

epithelial cells and mucin (Soufrant, 1991; Grala et al., 1998). The endogenous crude

21

w.

 

protein and AA losses are divided into two origins: basal (minimum) and specific
endogenous losses. The basal loss is non-specific and related to dry matter intake,
whereas the specific loss is related to inherent factors in the feedstuff, e. g. fiber and anti-
nutn’tive factors (Rademacher et al., 1999). The feeding of a protein-free diet is one of the
most common methods used to estimate basal ileal endogenous secretions. It is believed
with this method that all nitrogen-containing compounds in the digesta are of endogenous
origin. However, a problem associated with this method is that a protein-free diet fed to
growing pigs may overestimate endogenous proline recovery as compared with feeding a
protein-containing diet (de Lange et al., 1989). Thus, the proline recovered from a
protein-free diet can then make up 30 % or more of the total amount of AA in the digesta.
These high levels of proline are never observed when other methods are used. Another
commonly used method is feeding a highly digestible protein source (e. g. wheat gluten or
casein). With this method, it is assumed that the digestibility of these protein sources are
99%, and that the AA are completely absorbed. The regression method is another method
for estimating endogenous losses, in which pigs are fed graded levels of protein in the
diet and the recovery of N and AA at the terminal ileum is related to N and AA intake.
Thus, via mathematical extrapolation, the recovery of N and AA at zero N and AA intake
can be estimated (Fan et al., 1995). A final method that is not as commonly used as the
above methods involves feeding a diet in which the sole source of N is enzymatically
hydrolyzed casein. This hydrolyzed casein contains approximately 6 % free AA and 41 %
di- and tri-peptides with a molecular weight of less than 5,000 Dalton (Da) (Leteme et al.,
1994). It is assumed that all endogenous N is found in the ultrafiltrated fraction of the

digesta with molecular weights greater than 10,000 Da. Thus, by separating the low

22

 

(<5,000 Da) and the high (>10,000 Da) molecular weight N-containing compounds in
ileal digesta, a distinction is made between non-absorbed exogenous and endogenous

nitrogen.

Factors that affect endogenous losses

Secretion of endogenous N is influenced by a number of animal factors, such as age
and body weight, and several dietary factors (Nyachoti et al., 1997). The dietary factors
that affect endogenous N losses include dry matter (DM) intake (Butts et al., 1993), level
and quality of dietary protein (de Lange et al., 1990), and the presence of anti-nutritional
factors, such as trypsin inhibitors and lectins (Schulze, 1995). Grala et al. (1998) found
that a high trypsin inhibitor activity in soybean products fed to pigs was associated with
high ileal losses of endogenous N. Fiber can also influence the secretion of endogenous
gut proteins and N. Schulze et al. (1995) showed that increased dietary neutral detergent
fiber content increased ileal DM and N flow, reduced N utilization, and resulted in an
increased endogenous N loss. Therefore, the relationship between the amount of
endogenous protein secreted into the gut and the endogenous N losses are dependent on

the type of diet fed to pigs (Schulze, 1995; Grala et al., 1998).

True digestibility

True digestibility adjusts apparent digestibility measurements by correcting for
endogenous N secretions. As a consequence, true digestibility values should be
unaffected by the cmde protein (CP) content of the diet (Batterham, 1994). Therefore, it

can be assumed that true digestibility is a more accurate measurement of ileal AA

23

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digestibility. However, true digestibility does not account for diet specific endogenous

losses.

Standardized ileal digestibility

Recent research from France and the Netherlands has addressed the problem
associated with true digestibility and diet specific endogenous losses. According to a
reseach review by Rademacher et al. (1999), endogenous protein and AA losses can be
separated into a basal (minimum) and an additional specific loss. The basal loss is non-
specific and related only to DM intake. However, the specific losses are associated with
the nutrient quality and inherent factors in the feedstuffs, i.e., fiber and anti-nutritive
factors. If corrections are made for basal endogenous AA losses, then the corrected
“standardized” ileal AA digestibility coefficients are independent of the AA levels within
the diet. Therefore, apparent AA digestibility coefficients can be easily modified to

standardized digestibility coefficients.

Conclusion
From the above literature, it is obvious that there are several advantages to feeding
specialty corn hybrids. However, there are limited published values in terms of nutrient
digestibility of these corn hybrids. Further research into protein, amino acid, and starch
digestibility is warranted. Therefore, it is the objective of this thesis to determine the
starch digestibility, protein digestibility, and protein utilization of waxy, high-oil, and

high-lysine corn varieties.

24

 

CHAPTER 2: APPARENT AND STANDARDIZED ILEAL AMINO ACID
DIGESTIBILITIES OF VARIOUS NUTRIENT-DENSE CORN HYBRIDS FED
TO GROWING PIGS

Abstract

Eight ileally cannulated Yorkshire barrows (44.54 i .80 kg) were used in an 8 x 8
Latin square design to determine apparent and standardized amino acid digestibilities
among various nutrient-dense corn hybrids. The corn hybrids used in the study were:
high-oil (HO), high-oil paired normal (HOPN), high-lysine (HL), high-lysine paired
normal (HLPN), waxy (WX), waxy paired normal (WXPN), and normal yellow dent corn
(NYD). Each diet consisted of one of the respective test corn hybrids (96.6%) providing
the sole source of energy and protein. An additional 3.15% of the diet was made up of
vitamins, minerals, dicalcium phosphate, limestone, and salt, which met or exceeded
nutrient requirements of growing pigs (NRC, 1988). Chromic oxide (0.25%) was added
as an indigestible marker. An amino acidtop dress was also applied to the diets to meet
or exceed NRC (1988) amino acid requirements for growing pigs. Pigs were allowed a 5-
day adaptation to experimental diets, followed by two 12-hr digesta collections on d 6
and 7. The amino acid top dress was removed on d 5 of adaptation. A protein-free diet
consisting of 81.93% cornstarch, 5% solka floc, 4% corn oil, and 5% sugar was fed to
estimate endogenous amino acid losses at the terminal ileum. Apparent threonine (Thr),
and alanine (Ala) digestibility coefficients for H0 and HI. were lower (P S .10) than their
respective paired normal corn hybrids, HOPN and HLPN. In addition, standardized Phe,
Thr, and Ala digestibility coefficients for H0 and HL were lower (P s .10) than the
paired normal corn hybrids, HOPN and HLPN. Overall, the hybrids had similar

digestibility coefficients as compared to their respective paired normal corn hybrids.

25

 

Introduction

Many studies conducted by nutritionists indicate that formulating swine diets based on
digestible rather than total amino acid content results in a better prediction of
performance (Rademacher et al., 1999). Therefore, determining the amino acid utilization
of various feedstuffs in growing pigs, the potential for obtaining maximum growth
performance at cost effective rates is within our grasp. Recently, the use of “nutrient-
dense” corn grains in swine diets has provided an alternative to feeding normal yellow
dent corn to growing pigs. However, little is know about the amino acid availability and
utilization of these corn hybrids in growing pigs. Thus, the goal of the present study was
to determine the apparent and standardized ileal amino acid digestibility coefficients of
high-oil corn, high-lysine corn, waxy corn, and their respective paired normal corn
hybrids when fed to growing pigs.

Materials and Methods

Six corn hybrids: high-oil (HO; Cargill LH 202), high-oil paired normal (HOPN;
Cargill 5990), waxy (WX; Pioneer 3528E), waxy paired normal (WXPN; Pioneer 3527),
high-lysine (HL; Crows SL20), and a high-lysine paired normal (I-ILPN; Crows 375)
were obtained from different commercial seed companies. The three seed companies
provided the specialty corn hybrids along with their respective paired normal corn
hybrids. An additional yellow dent corn (NYD; Citizens Elevator, Charlotte, MI) was
used to represent a control, which had no known genetic similarities to that of the other
six corn hybrids.

According to Jones and Andersen (1999), delayed planting combined with below
normal temperatures for the 1997 growing season resulted in a corn crop that was 2-3 wk

behind normal crop development. This made the 1997 corn crop more vulnerable to early

26

frost damage before it reached maturity. Even if the corn was not damaged by frost, Jones
and Andersen (1997) stated that immature corn would most likely exhibit a higher
moisture, which would increase drying costs, and have a lower test weight. Therefore,
harvest conditions for fall 1997 were not optimal for a good corn harvest in Michigan.

Eight Yorkshire barrows, with an initial average body weight of 40 kg, were fitted
with simple T cannulas at the terminal ileum. Cannulas were surgically fitted and
maintained according to Stein et a1. (1998). The barrows were moved to smooth sided
individual pens (1.78 m x 0.76 m) immediately following surgery and allowed 21 days of
recuperation. NaxcelTM (3 cc per pig, Pharmacia and Upjohn Co., Kalamazoo, MI) was
administered for the first three days post surgery. Daily feed intake, internal body
temperature, and integrity of the cannulas were monitored daily during the recovery
period. All pigs had free access to water. At the end of the recovery period, pigs were
randomly assigned to one of seven corn hybrid diets plus a protein free diet in the 8 x 8
Latin square designed experiment. The pigs were allowed five days to adjust to the diets.
On d 6 and 7 of each period, digesta was continuously collected from each pig for 12 h.
Pigs were weighed at the beginning and at the end of the trial. Initial average body weight
was 44.5 i .8 kg and the final average body weight was 64.2 i 1.5 kg. Environmental
temperature of the room ranged from 21 to 28°C with a mean temperature of 21°C. The
Michigan State University All University Committee for the Use and Care of Animals
approved all animal protocols.

Diets

Each corn hybrid provided 96.6% of the total diet. Vitamins, minerals, dicalcium

phosphate, limestone, and salt were included at 3.15% of the test corn diets. A protein

27

free diet containing 81.93% cornstarch, 5% sugar, 5% solka flock, and 4% corn oil was
also provided. Vitamins, minerals, dicalcium phosphate, limestone, and salt were
included at 3.82% of the protein free diet. All vitamins and minerals met or exceeded
NRC (1988) requirements. Chromic oxide was included at 0.25% of the diets as the
marker for the determination of the recovery of protein and amino acids in the ileal
digesta (Table 1). Barrows were allowed ad libitum access to feed during the three-week
post-surgical recovery period and then restricted to approximately 90% of ad libitum
intake during the experiment. Average daily feed intake (ADFI) was recorded by
measuring daily feed allocations and then weighing back any waste feed. Diets were
offered in two equal sized meals daily. An amino acid top dress was added to each meal
during the adaptation period to meet the amino acid requirements for the seven deficient
amino acids: lysine,- methionine, isoleucine, threonine, valine, phenylalanine, and
tryptophan (NRC, 1988). Amino acid top dresses were removed one day prior to the two-
day digesta collection. The inclusion rates of the seven amino acids are reported in Table
4 in g/kg of diet for growing pigs between 50 and 80 kg. In addition, lysine intake was
calculated for both the 5-day adaptation period in g/d and the 2-day collection period in
g/d (Table 5).
Sample Preparation and analysis

Collected digesta and samples from each pig were homogenized and pooled over the
2-day collection and stored at -20°C until samples were prepared for further analysis.
Digesta samples were thawed, freeze-dried, and finely ground through a cyclone mill
(Cyclotec Sample Mill 1093; Tecator C0,, Hoganas, Sweden) for dry matter (DM), crude

protein (CP), amino acid (AA), and chromium analysis. Dry matter content of each com

28

sample, each diets, and each digesta sample was determined using a vacuum oven at
60°C for sixteen h. Gross energy of each corn hybrid sample and diet was determined via
adiabatic bomb calorimetry (Parr Instrument Co., Moline, IL). Crude protein content of
the respective test corn hybrid was determined using an automated LECO® elemental
analysis instrument (AOAC # 990.03, crude protein and animal feeds; LECO‘ID FP-2000;
LECO Co., St. Joseph, MI).

Amino acid determination was performed using the Pico Tag® method (Waters Co.,
Milford, MA) which included acid hydrolysis of samples in an autoclave for 24 h at
110°C. Samples were then brought up to a volume of 40 mL, homogenized and filtered.
The AA filtrate was then sub-sampled and dried using high-speed vacuum centrifugation.
The AA hydrolysate was then reconstituted, re-dried, and derivatized with PITCQ and
separated using a Waters high pressure liquid chromatographer (Waters, Co., Milford,
MA) fitted with a 15 cm hydrolysate column (Pico Tag® free amino acid analysis
column, 3.9 mm x 300 mm; flow rate of 1 mL per min).

Chromium (Cr) concentration in diets, digesta and fecal matter was determined via
perchloric digestion (Cantle, 1982). A 0.3 g sample was digested using 20 mL
concentrated nitric acid and heated. After digestion, 10 mL of perchloric acid was added
to oxidize the Cr3+ to Cr“. Oxidation completion was indicated when the solution turned
from a bright orange to a clear, pale yellow. Samples were then weighed, diluted and
analyzed by atomic absorption spectrophotometry (Unicam 93, TJA Unicam Co.;
Cambridge, UK).

Statistical analysis

29

Data was analyzed using the Mixed procedure of SAS (1998) for amino acid
digestibility in a Latin square design. A linear model with main effects of period, diet,
and pig were used to test the dependent variable: amino acid digestibility. Three
orthogonal and Three non-orthogonal contrasts were used to determine differences
between the following pre-planned comparisons: HO vs. HOPN, WX vs. WXPN, HL vs.
HLPN, HO vs. the four control corn hybrids (HOPN, WXPN, HLPN, and NYD), WX vs.
the four control corn hybrids, and HL vs. the four control corn hybrids at one levels of
significance (P < .05). The General Linear Model procedure of SAS (1998) was used to
determine if pig and period were significant within the model. Both pig and period were
found to be significant (P < .05), except for Thr, His, and Asp. The apparent and
standardized amino acid-digestibilities by age of pigs in weeks are found in Appendices
B,C,DandE. .. '. 1‘

Results ~

Table 2 represents the chemically determined nutrient composition of the seven corn
hybrids. Dry matter and gross energy was similar across all seven com hybrids. Crude
protein ranged from 6.88 to 8.39% in the corn varieties with HOPN having the lowest
protein content and HLPN having the highest protein content. The HO hybrid had the
lowest ether extract at 3.52% while all the other com hybrids ranged from 3.85 to 5.54%.
Amino acid content of the corn hybrids were determined on a dry matter basis (Table 2).
The highest lysine content was found in the HL hybrid at 0.30%. Arginine (Arg),
histidine (His), isoleucine (Ile), leucine (Leu), phenylalanine (Phe), threonine (Thr), and
valine (Val) concentrations ranged from 0.39 to 0.53, 0.29 to 0.37, 0.23 to 0.33, 0.60 to

1.00, 0.31 to 0.42, 0.23 to 0.32, and 0.36 to 0.43, respectively. Dry matter was similar

30

 

 

 

cl;

across all test corn hybrids (Table 2). Gross energy was highest in the HOPN diet at 4.78
Meal/kg and lowest in the NYD diet at 4.35 Meal/kg. All the other test diets contained
approximately 4.51 Mcal/kg (Table 2).

Average daily feed intake ranged from 1.77 to 1.98 kg/d with a mean of 1.86 kg/d.
Lysine intake (Table 5) during the adaptation period was highest in the HO diet at 20.77
g/d and lowest in the WXPN diet at 18.23 g/d. Lysine intake during the collection period
was highest in the HL diet at 5.85 g/d and the lowest in the HLPN diet at 3.55 g/d.

Apparent indispensable ileal amino acid digestibilities (AIID) are reported in Table 6.
There were no differences in AIID (P > .05) observed between WX vs WXPN and WX
vs. the average of the four control corn hybrids (HOPN, WXPN, HLPN, and NYD). The
HO corn had less (P < .05) Ile, Thr, Val, and lysine (Lys) than the HOPN corn hybrid.
The HO had less (P-< .05) Ile, Lys, Phe, Thr,: and “Val than the average of the four control
corn hybrids. The HL corn had less (P < .05) Leu, Phe, and Thr than the HLPN corn. The
HL corn had less (P < .05) Leu, Phe, and Thr than the average of the four control corn
hybrids. Total AIID was lower (P < .05) in H0 for the comparisons HO vs. HOPN and
H0 vs. the four control corn hybrids.

Apparent dispensable ileal amino acid digestibilities (ADID) are reported in Table 7.
There were no significant differences in ADID (P > .05) reported between WX and
WXPN. However, the WX corn had less (P < .05) aspartate (Asp) and higher (P < .05)
glutamate (Glu) and proline (Pro) than the average of the four control corn hybrids. The
HO corn had less (P < .05) alanine (Ala) and Asp than the HOPN corn. Furthermore, the
comparison between HO and the four control corn hybrids resulted in lower (P < .05)

values for Ala and Gly in H0. The HL corn had less(P < .05 ) Ala and Pro, and higher

31

 

(J

11

 

 

 

Asp (P < .05) than the HLPN corn. In addition, the HL had less Pro (P < .05), and higher
Asp (P < .05) than the average of the four control corn hybrids.

Standardized ileal amino acid digestibilities in Table 9 and 11 were calculated using
the endogenous amino acid losses (mg/kg DMI) reported in Table 8. Standardized ileal
digestibilities for the indispensable amino acids (SIID) are reported in Table 9 and 11.
Values from Table 9 ranged from 71.90 to 95.30%. Values from Table 11 represent SIID
values obtained from using endogenous amino acid losses from Rademacher et al. (1999),
and ranged from 79.17 to 96.33%. No differences in SIID were detected for the
comparison of WX vs. WXPN and WX vs. the average of the four control corn hybrids
(Table 9 and 11). The HO corn had less (P < .05) Ile, Lys, Phe, and Val than HOPN
(Table 9 and 11). Also,'the HO corn hybrid had less (P < .05) Ile, Lys, Phe, Thr, and Val
than the average of the four controLcorn hybrids (Table 9). The HL corn had less Arg,
Leu, Phe, Thr (P. < .05; Table 9~and 11). Ile, and Val (Table 11) than HLPN. However,
only Thr and Phe was lower (P < .05) in the HL corn as compared to the average of the
four control corn hybrids (Table 9 and 11).

Standardized dispensable ileal amino acid digestibilities (SDID) are reported in Table
10 and ranged from 64.87 to 132.65%. There were no differences reported for WX vs.
WXPN and WX vs. the average of the four control corn hybrids. The HO corn had less (P
< .05) Ala than the HOPN corn. Also, the HO corn had less (P < .05) Ala and Gly than
the average of the four control corn hybrids. The HL corn had less (P < .05) Ala, Pro, Ser,
and Gly than the HLPN corn. In addition, Asp was higher (P < .05) and Pro (P < .05) was

lower in the HI. corn, as compared to the average of the four respective control com

32

 

 

rcpt
20m
slmé

Ser,

 

 

amzi
\\ alui

8510,

hybrids. The only difference found for total SDID was between HL and HLPN, in which
HL was lower (P < .05) than HLPN.
Discussion

The amino acid compositions of the corn hybrids were similar to other reported values
for high-oil, high-lysine, and waxy corn (Cromwell et al., 1967; Adams and Jensen, 1987;
Adeola and Bajjalieh, 1997; Burgoon et al., 1992; Nordstrom et al., 1972; Rosa et al.,
1977; Wahlstrom et al., 1977; Parsons et al.,1998; and Snow et al., 1998). However,
reported values for Leu concentration tended to be numerically higher as compared to our
reported values.

The ratio of Lys as a percent of crude protein from HL and NYD were similar to
reported values of Pond and Maner (1984) and Cromwell et al. (1967). Amino acid
concentrations as a percent of crude=protein for ‘HL corn from the present study were
similar to reported values of Cromwell et al. (1967) for Arg, His, Thr, Val, Asp, Gly, and
Ser; but lower for Ile, Leu, Phe, Ala, Glu, Pro, and Tyr. In addition, all the indispensable
amino acid ratios as a percent of crude protein for NYD were within range of published
values (Pond and Maner, 1984; Cromwell et al., 1967); but all the dispensable amino
acids ratios, except Ala and Ser, were lower than published values.

Apparent indispensable amino acid digestibilities for high-lysine corn fell within
range of published values reported by Burgoon et al. (1992); but were higher than
reported values from Snow et al. (1998). Apparent indispensable amino acid
digestibilities for waxy corn from this study were higher than other published values (
Soltwedel, 1996; Snow et al., 1998); except for Lys, which fell within the ranges of other

reported values (Soltwedel, 1996; Snow et al., 1998). Apparent indispensable amino acid

33

 

19v

‘\ 8i

‘36"

or

‘I
in“
~.

‘

digestibility values for high-oil corn from this study were low for Ile and Lys, and high
for His as compared to Carr (1994), Soltwedel (1996), and Snow et al. (1998). However,
all other AIID fell within range of published values (Carr, 1994; Soltwedel, 1996; and
Snow et al., 1998). In addition, all AIID for normal yellow dent corn fell within range of
other published values (Sauer et al., 1977; Carr, 1994; Soltwedel, 1996; and Snow et al.,
1998). Differences in ADID were observed in H0, HL, and NYD when comparing our
values with published values from Snow et al. (1998). Our ADID values for H0 corn
were lower than reported values by Snow et al. (1998); however, our values for HI. and
NYD were numerically higher. In the present study, the apparent amino acid digestibility
in H0 was much lower than in HOPN. This may have been due to poor harvest
conditions. Also, our HO results contradicted results reported by Snow et al. (1998), in
which the HO hybrid out performed the HOPN. corn for apparent amino acid digestibility.
However, in the present study, the HLPN'corn out performed the HL hybrid for apparent
amino acid digestibility, which follows results reported by Snow et al. (1998) and
suggests that the HLPN corn was superior to the HL hybrid.

A study conducted by Carlson and Bayley (1970) showed that endogenous amino acid
losses could not be quantified when feeding a protein-rich diet; therefore, a protein free
diet must be fed to account for endogenous ileal amino acid losses. Tavemer (1981)
reported that when protein free diets were fed, the greatest endogenous amino acids
recovered in the ileal digesta were (in order from highest to lowest) proline, glycine,
glutamic acid, aspartic acid, serine and threonine. De Lange et al. (1989) also reported
that regardless of the kind of protein free diets fed (cornstarch, pectin, cellulose, or fat-

based), the greatest endogenous losses at the distal ileum were proline, glycine, glutamic

34

acid, aspartic acid, arginine, and serine. The amount of endogenous amino acids
recovered at the terminal ileum were measured in the present study by feeding a protein
free diet, consisting primarily of cornstarch. From our trial, the five greatest endogenous
amino acid losses from highest to lowest were proline, glycine, glutamate, arginine, and
alanine (Table 8). Therefore, our results follow closely with Tavemer (1981) and de
Lange’s (1989) published values. In addition, our value for average endogenous arginine
losses, 420 mg/kg of DMI, at the terminal ileum was higher than the reported values from
feeding a protein free diet (Rademacher et al., 1999) and averaged values determined
from five different methods from Rademacher et al. (1999). The rest of our amino acid
losses at the terminal ileum were lower as compared to protein free values and averaged
values from five different methods reported by Rademacher et al. (1999); however,
values for the indispensable amino acids are not reported.

Standardized digestibility values for these nutrient-dense corn hybrids have not been
published; however, Jondreville et al. (1995) and Rademacher et al. (1999) have
published SIID values for normal dent corn. The SIID values from the present study were
lower than published values reported by Jondreville (1995) and Rademacher et al. (1999),
except for histidine, which was higher in the present study. However, our values for AIID
for NYD were similar, if not the same, as values reported by Rademacher et al. (1999) for
AIID. Thus, the differences in SIID for NYD are most likely due to endogenous
secretions as mentioned above. Also, the standardized HO and HL amino acid
digestibility values were lower as compared to the HOPN and HLPN digestibility values.
This was not expected. Furthermore, the high-oil corn tested in this study had a lower oil

content as compared to its respective paired normal corn, which probably contributed to

35

the results that we obtained. In addition, the HLPN corn consistently outperformed the
HL hybrid for feed intake, feed efficiency, and amino acid digestibility. The lower oil
content in the HO hybrid and the poor performance of both the HO and HL hybrids may
have been due to the poor growing and harvesting conditions in 1997. Therefore, we can
assume that the HO and HL hybrids in the present study were not true ‘nutrient-dense’
corn hybrids. In the case of WX vs. WXPN for both apparent and standardized
digestibility, no differences were detected. Furthermore, the WX hybrid was, in some
cases, lower in apparent and standardized dispensable amino acid digestibility, when it
was compared to the four control corn hybrids. Therefore, the amylopectin starch was
probably not as readily digested by the pig as previously thought.

Table 11 represents SIID values using the averaged endogenous amino acid losses
reported by Rademacher et al. (1999). These values were compared to the SIID values we
calculated using the endogenous amino acid losses obtained from feeding a protein free
diet (Table 9). Since our endogenous amino acid losses for arginine were higher than
values reported by Rademacher et al. (1999), our SIID values were also numerically
higher. However, the SIID values using Rademacher et al. (1999) averaged endogenous
amino acid losses were numerically higher than our reported values for histidine,
isoleucine, leucine, lysine, phenylalanine, threonine, and valine. Overall, our calculated
SIID values were relatively close to calculated SIID values using Rademacher et al.
(1999) averaged endogenous amino acid losses.

Implications
Apparent and standardized amino acid digestibility coefficients for nutrient-dense corn

hybrids are now available. Amino acid digestibility in specialty corn hybrids was similar

36

or in some cases higher when compared to normal dent corn. However, the year to year
variability within corn hybrids makes it difficult to obtain consistent digestibility

coefficients. Thus, more amino acid digestibility data of nutrient-dense corns are needed.

37

 

:

(or

Die

Lirr

Vltl

Table 1: Composition of experimental diets (as-fed basis, %)

”

 

 

Diets

Ingredients Com-based Protein free
Corna 96.60 —

Cornstarchb I — 8 1 .93
Solka flockc —— 5.00
Sugar — 5.00
Corn oil“ — 4.00
Dicalcium phosphate 1.25 2.70
Limestone ‘ 0.85 ‘ 0.07
Vitamin premixe -‘0.50 A 0.50
Trace mineral premixf ' 0.25 0.25
Salt 0.30 0.30
Chromic oxideg 0.25 0.25

 

a Corn varieties used were normal yellow dent corn (NYD), waxy (WX), waxy paired
normal (WXPN), high-oil (HO), high-oil paired normal (HOPN), high-lysine (HL),
andhigh-lysine paired normal (HLPN).

b Argo Foods, CPC International, Inc., Englewood Cliffs, NJ 07632-9976.

° Harland Teklad, Madison, WI 53744-4220.

d Kraft Foodservice, Inc., Glenview, IL 60025.

e Provided the following per kilogram of diet: 4,583 IU vitamin D3, 55 IU vitamin E, 11
mg vitamin K, 3.66 mg menadione, 0.0275 mg vitamin B”, 3.66 mg riboflavin, 14.67
mg d-pantothenic acid, 22 mg niacin, 0.913 mg thiamine, 0.825 mg pyridoxine.

fProvided the following per kilogram of diet: 335 g Ca, 5 g Fe, 5 g Zn, 5 mg Cu, 5 mg
Mn, 150 pg Se and 75 pg 1.

g Fisher, Itasca, IL 60143.

38

Table 2: Nutrient composition of corn hybridsa (dry matter basis)

 

 

Items HO HOPN WX WXPN HL HLPN NYD

 

Dry matter, % 86.35 85.73 84.97 85.85 86.45 86.03 86.12
Crude protein, % 7.09 6.88 7.31 7.33 7.97 8.39 8.34

Gross energy, 4.58 4.78 4.27 4.50 4.61 4.60 4.35

Meal/kg

Ether Extract, % 3.52 5.54 4.24 4.01 4.50 3.85 4.00

Amino acids, %

Indispensable

Arg 0.43 0.41 0.40 0.39 0.53 0.42 0.40
His 0.30 0.29 0.29 0.30 0.37 0.33 0.34
Ile 0.23 0.24 0.26 0.23 0.26 0.29 0.33
Leu 0.74 0.70 0.71 0.73 0.60 0.94 1.00
Lys 0.19 0.20 0.21 0.21 0.30 0.22 0.20
Phe 0.32 . 0.31 0.32 . 0.32 0.31 0.39 0.42
Thr 0.23 " 0.27 ‘ ' 0.26 0.24 0.26 0.32 0.31
Val 0.36 0.36 0.36 0.37 0.42 0.42 0.43

Dispensable
Ala 0.50 0.49 0.49 0.50 0.48 0.61 0.62
Asp 0.36 0.45 0.39 0.48 0.66 0.36 0.28
Glu 1.05 1.11 1.09 1.13 1.15 1.16 0.92
Gly 0.27 0.28 0.28 0.27 0.34 0.30 0.29
Pro 0.57 0.51 0.56 0.54 0.58 0.96 0.71
Ser 0.38 0.34 0.35 0.35 0.36 0.39 0.42
Tyr 0.27 0.27 0.28 0.28 0.30 0.32 0.31

ZAmino Acids 6.20 6.23 6.25 6.34 7.22 7.43 6.98

 

a Corns tested were high-oil (HO), high-oil paired normal (HOPN), waxy (WX), waxy
paired normal (WXPN), high-lysine (HL), high-lysine paired normal (HLPN), and a
normal yellow dent corn (NYD).

39

Table 3: Amino acid concentration as a percent of total crude proteinab

 

 

Amino acid HO HOPN WX WXPN HL HLPN NYD

Indispensable
Arg 6.06 5.96 5.47 5.32 6.65 5.01 4.80
His 4.23 4.22 3.97 4.09 4.64 2.93 4.08
Ile 3.24 3.49 3.56 3.14 3.26 3.46 3.96
Leu 10.44 1.02 9.71 9.96 7.53 ' 11.20 11.99
Lys 2.68 2.91 2.87 2.86 3.76 2.62 2.40
Phe 4.51 4.51 4.38 4.37 3.89 4.65 5.04
Thr 3.24 3.92 3.56 3.27 3.26 3.81 3.72
Val 5.08 5.23 4.92 5.05 5.27 5.01 5.16

Dispensable
Ala 7.05 7.12 6.70 ' 6.82 6.02 7.27 7.43
Asp 5.08 6.54 5.34 6.55 8.28 4.29 3.36
Glu 14.81 16.13 14.91 15.42 14.43 13.83 11.03
Gly 3.81 4.07 3.83 3.68 4.27 3.58 3.48
Pro 8.04 7.41 7.66 7.37 7.28 11.44 8.51
Ser 5.36 4.94 .479 4.77 4.52 4.65 5.04
Tyr 3.81 3.92 3.83 3.82 3.76 3.81 3.72

 

a Corns tested were high-oil (HO), high-oil paired normal (HOPN), waxy (WX), waxy
paired normal (WXPN), high-lysine(1-IL), high-lysine paired normal (HLPN), and
normal dent corn (NYD).

Calculated as (% amino acid / % protein) x 100.

40

Table 4: Amino acid top dress composition“be (g/kg)

 

 

Amino acid HO HOPN WX ‘ WXPN HL HLPN NYD
Ile 1.86 1.76 1.65 1.80 1.63 1.32 .933
Leu — .150 — — 1.06 — —
Lys 6.89 6.71 6.57 6.57 5.48 6.50 6.66
Met .070 .160 .010 — .120 —— .050
Phe 1.18 1.34 1.20 1.19 1.30 .550 .160
Thr 2.82 2.43 2.49 2.70 2.46 1.93 1.96
Trp 1.70 1.70 ' 1.70 - 1.70 1.70 1.70 1.70
Val 1.60 1.57 1.56 1.50 .983 .958 .908

 

‘ Corns tested were high-oil (HO), high-oil paired normal (HOPN), waxy (WX), waxy
paired normal (WXPN), high-lysine (HL), high-lysine paired normal (HLPN), and
normal dent corn (NYD).

b Amino acid top dress = amino acid requirement (NRC, 1988) for 50 to 80 kg pigs —
amino acid content in the corn varieties.

° Added back to the test diets to meet the amino acid requirements.

41

Table 5: Lysine and feed intake of growing pigs fed corn hybridsa

HO HOPN wx WXPN HL HLPN NYD P1:b

 

Feed intakec, 2.38 2.34 2.28 2.10 2.17 1.97 2.39 1.96
kg/d

Lysine intaked, 20.77 20.42 19.85 18.23 18.43 17.10 20.76 —
g/d

Feedintakee, 2.06 1.99 1.98 1.97 1.95 1.64 2.05 1.70
kg/d

Lysine intakef, 3.81 3.99 4.19 4.18 5.85 3.55 4.17 —
g/d

 

a Corns tested were high-oil (HO), high-oil paired normal (HOPN), waxy (WX), waxy
paired normal (WXPN), high-lysine.(HL), high-lysine paired normal (HLPN), and
bnormal dent corn (NYD).
bA protein free (PF) diet was feed.

° dAverage daily feed intake during five-day adaptation to test diets.
dAverage daily lysine intake during five-day adaptation to test diets.

:Average daily feed intake during two-day digesta collection.
Average daily lysine intake during two- day digesta collection

42

Table 6: Apparent indispensable amino acid digestibilities of the corn hybridsa (%)

 

Pooled
Ho° HOPN wx WXPN HL HLPN NYD SEM”
N 8 8 8 8 8 8 8
Indispensable
Arg 74.95 77.27 74.28 76.58 77.26 82.74 74.91 2.75
His 85.75 88.01 86.77 88.24 88.57 88.32 86.54 1.07
Ile 67.48’ 74.60‘ 75.26 71.08 71.19 75.54 75.57 2.06
Leu 79.20 81.64 82.64 81.74 7805“ 84.71‘ 81.53 1.60
Lys 56.98‘ 65.89‘ 65.18 65.49 68.84 66.12 61.90 2.32
Phe 77.66' 81.00 81.62 80.45 - 77.18‘ 82.12‘ 80.66 1.54
Thr 60.99‘ 68.59' 66.27 65.67. 60.66‘ 71.23‘ 70.63 2.40
Val 70.26‘ 75.49‘ 75.46 74.62 72.86 76.1 1 74.44 1.84
Mean 7166* 76.56‘ 75.94 75.48 74.32 78.36 75.77 1.68

 

a Corns tested were high-oil (HO), high-oil paired normal (HOPN), waxy (WX), waxy
paired normal (WXPN), high-lysine (HL), high-lysine paired normal (HLPN), and
normal yellow dent corn (NYD).

b Pooled SEM represents the square root of the mean standard error divided by n.

C If the superscript is on the paired normal com, the comparison is between the hybrid and
the respective paired normal com. If the superscript is on the corn hybrid, the
comparison is between the hybrid and the four control corns (HOPN, WXPN, HLPN,
NYD).

' Means in rows with different superscripts are different (P<.05).

43

Table 7: Apparent dispensable amino acid digestibilities of the corn hybrids“ (%)

 

 

 

 

 

Hoc HOPN wx WXPN HL HLPN NYD * Pscgriiibd
N 8 8 8 8 8 8 8
Dispensable
Ala 6797“ 74.68‘ 73.55 73.12 70.61 79.21’ 72.04 2.39
Asp 69.08 79.32‘ 74.50‘ 75.46 81.77’ 71.71‘ 57.70 3.67
Glu 76.00 80.24 80.23' 79.16 79.66 78.75 67.55 1.75
Gly 2806’ 35.95 35.33 32.43 39.18 49.56 37.32 ' 6.95
Pro 1.52 -221 -1701" -450 -2071‘ 76.96‘ 26.11 19.20
Ser 74.46 74.44 74.41 75.66 . 72.05 75.97 75.32 1.73
Tyr 78.50 81.44 82.25 81.34 79.67 82.46 79.45 1.60
Mean 56.51 60.55 57.61 58.96 57.46 73.52‘ 59.35 1.60

 

" Corns tested were high-oil (HO), high-oil paired normal (HOPN), waxy (WX), waxy
paired normal (WXPN), high-lysine (HL), high-lysine paired normal (HLPN), and
normal yellow dent corn (NYD).

b Pooled SEM represents the square root of the mean standard error divided by n.

C If the superscript is on the paired normal com, the contrast is between the hybrid and
its respective paired normal com. If the superscript is on the corn hybrid, the
contrast is between the hybrid and the four control corns (HOPN, WXPN, HLPN,
and NYD).

‘ Means in rows with different superscripts are different (P<.05).

44

Table 8: Average values of the amount of endogenous AA losses determined at the

terminal ileum with a protein free diet (mgkg DMI)a

Rademacher et a1. Rademacher et a1.

 

Amino Acid ‘ Protein fi'ee dietb Protein free diet° Avg Valuesd

Indispensable
Arg 420 i 63 400 :h 80 390
His 118i17 160i20 190
Ile 204 i 18 290 :t 80 380
Leu 327 :1: 28 440 i 10 490
Lys 203 i 24 360 :t 10 400
Phe 181:1:14 310i70 340
Thr .' 338i27 510i80 610
Val ' ' 287$ 27 ' 410 i 90 540

Dispensable
Ala 415 i 46 — —
ASP 256 a 41 _ _
Glu 561 i 60 — —
Gly 1027i 143 — —
Pro 4313 i 1019 - -
Ser 329 i 12 — -
Tyr 160 i 12 _ _

 

‘ DMI = Dry matter intake

b Average endogenous AA losses determined by using a protein free diet (Andersen,
2000)

c Average endogenous AA losses obtained from Rademacher et a1. (1999) using a protein
free diet.

d Average endogenous AA losses obtained from Rademacher et al. (1999) from five
different methods (Protein free diet, wheat gluten/casein, regression analysis,
enzymatically hydrolyzed casein, and infusion).

45

Table 9: Standardized indispensable amino acid digestibilities of the corn hybrids“ (%)

 

 

 

Pooled
Hod HOPN wx WXPN HL HLPN NYD SEM“
N 8 8 8 8 8 8 8
Indispensable
Arg 85.62 87.93 84.99 87.61 85.52 95.30‘ 85.61 3.19
His 89.64 92.81 90.90 92.22 91.91 92.81 90.10 1.19
Ile 76.00‘ 83.26‘ 83.33 80.10 79.47 84.34 81.84 2.22
Leu 83.36 86.35 87.13 86.12 83.501 88.90‘ 84.71 1.59
Lys 67.71‘ 7641‘ 74.83 75.28 75.88 77.75 71.90 2.65
Phe 83.16" 7.13‘ 87.32 86.21 8326‘ 87.97‘ 84.95 1.63
Thr 75.49' 81.71 .. 79.32 80.05 74.01‘ 84.49' 81.46 244
Va] 7806’ 83.68‘ 83.40 82.55 79.95 84.53 81.17 1.98
Mean 79.76" 84.84‘ 83.90 83.76 81.69 87. 01‘ 82.72 1.87

 

aCorns tested were high-oil (HO), high-oil paired normal (HOPN), waxy (WX), waxy
paired normal (WXPN), high-lysine (HL), high-lysine paired normal (HLPN), and

normal yellow dent corn (NYD).

b Calculated using endogenous amino acid losses obtained from feeding a protein free

diet.

C Pooled SEM represents the square root of the mean standard error divided by n.

d If the superscript is on the paired normal com, the contrast is between the hybrid and
its respective paired normal com..If the superscript is on the corn hybrid, the
contrast is between the hybrid and the four control corns (HOPN, WXPN, HLPN,

and NYD).

" Means in rows with different superscripts are different (P<.05).

46

Table 10: Standardized dispensible amino acid digestibilities of the corn hybridsab (%)

 

 

 

Pooled
HOd HOPN WX WXPN HL HLPN NYD SEMc
N 8 8 8 8 8 8 8
Dispensable
Ala 7616‘ 83.38. 82.13 81.63 79.63 87.64“ 78.75 2.59
Asp 76.05 85.21 81.10 80.94 85.80 80.67 67.03 3.67
Glu 81.23 85.47 85.42 84.24 84.75 84.76 73.68 1.82
Gly 64.87‘ 74.37 72.42 71.29 70.67 91.70' 72.58 i 8.53
Pro 75.42 85.09 60.88 76.93 56.96" 132.65‘ 87.47 22.89
Ser 82.98 84.56 83.84 85.15' 81.48 86.43. 83.27 2.04
Tyr 84.21 87.65 88.03 87.20 85.27 88.77 84.56 1.72
Mean 77.27 83.68 79.11 81.05 77.79 93.23‘ 78.19 5.38

 

a Corns tested were high-oil (HO), high-oil paired normal (HOPN), waxy (WX), waxy
paired normal (WXPN), high-lysine (HL), high-lysine paired normal (HLPN), and
normal yellow dent corn (NYD).

b Calculated using endogenous amino acid losses obtained from feeding a protein free

diet.

° Pool SEM represents the square root of the mean standard error divided by n.

d If the superscript is on the paired normal com, the contrast is between the hybrid and
its respective paired normal com. If the superscript is on the corn hybrid, the
contrast is between the hybrid and the four control coms (HOPN, WXPN, HLPN,
and NYD).

' Means in rows with different superscripts are different (P<.05).

47

Table 11: Standardized indispensable amino acid digestibilities of the corn hybrids
calculated using endogenous amino acid losses from Rademacher et al.” (%)

 

 

Pooled
Hod HOPN wx WXPN HL HLPN NYD SEM"

 

N 8 8 8 8 8 8 8

Indispensable

Arg 84.37 87.66 84.72 87.32 85.31 94.97‘ 85.33 3.18
His 92.32 95.14 93.75 94.96 94.21 95.90 92.56 1.35
Ile 84.15‘ 91.53‘ 91.02 88.71 87.37 92.75‘ 87.83 2.68
Leu 86.01' 89.30 89.91 88.95 86.92 91.52‘ 86.72 1.73
Lys 79.17‘ 8763' 85.13 85.72 83.38 90.17' 82.59 3.41
Phe 83.01" 8700‘ 88.T 17 86.04 83.14‘ 87.84‘ 84.85 1.57
Thr 88.46 93.43 9097 92.91 85.94‘ 96.33‘ 91.13 3.13
Val 85.66‘ 91.66‘ 91.14 90.26 86.86 92.73’ 87.73 2.43

 

3* Corns tested were high-oil (HO), high-oil paired normal (HOPN), waxy (WX), waxy
paired normal (WXPN), high-lysine (HL), high-lysine paired normal (HLPN), and
normal yellow dent corn (NYD).

b Calculated using endogenous amino acid losses from Rademacher et a1. (1999).

c Pooled SEM represents the square root of the mean standard error divided by n.

d If the superscript is on the paired normal com, the contrast is between the hybrid and
its respective paired normal com. If the superscript is on the corn hybrid, the
contrast is between the hybrid and the four control corns (HOPN, WXPN, HLPN,
and NYD).

’ Means in rows with different superscripts are different (P<.05).

48

CHAPTER 3: ILEAL STARCH, APPARENT PROTEIN, AND TRUE PROTEIN
DIGESTIBILITY VALUES FOR NUTRIENT-DENSE CORN HYBRIDS AND
THE RELATIONSHIP BETWEEN ILEAL STARCH AND THE FOLLOWING:
APPARENT PROTEIN, TRUE PROTEIN, AND STAN DARDIZED
INDISPENSABLE AMINO ACID DIGESTIBILITY

Abstract

Four ileally cannulated Yorkshire barrows (44.54 i .80 kg) were used in two consecutive
4 x 4 Latin square experimental designs (Year 1; Snow et al. 1998) and 8 barrows were
arranged in an 8 x 8 Latin square design (Year 2; Andersen, 2001) to determine ileal
starch digestibilities and the relationship between ileal starch digestibility and the
following: apparent protein, true protein, and standardized indispensable amino acid
digestibility among various corn hybrids. The corn hybrids, diets, and amino acid top
dress were the same: as described by Andersen (2001). Pigs were allowed a 5-day
adaptation to the test diets, followed by two 12-h digesta collections on d 6 and 7. Two
fecal grab samples were taken from each pig during each 12-h digesta collection True
protein digestibility of high-lysine paired normal (HLPN) (P < .05) was higher than the
true protein digestibility of high-lysine (HL), In addition, HLPN (P < .05) was higher
than HL for apparent protein digestibility. Year 2 ileal starch digestibility values were
numerically higher than Year 1 ileal starch digestibility values. For Year 2, high-oil (HO)
and HL (P < .05) com hybrids had higher ileal starch digestibility than the four control
corns (high-oil paired normal, HOPN; waxy paired normal, WXPN; HLPN, and normal
yellow dent, NYD). The higher starch digestibility for Year 2 was probably due to
variations in growing conditions from year to year. In addition, there was a positive
correlation (r = .175, P < .05) between ileal starch digestibility and apparent and true

protein digestibility.

49

Introduction

Many studies have determined protein, amino acid, and energy digestibility of various
feedstuffs in growing pigs; however, little data is available for starch digestibility.
Therefore, the objective of this study was to determine the ileal and fecal starch
digestibility of various “nutrient-dense” corn hybrids and the relationship between starch
digestibility and the following: protein and amino acid digestibility. Furthermore, we
hypothesized that the relationship between ileal starch digestibility and protein and
indispensable amino acid digestibility is positive and linear. In addition, we wanted to see
if there would be any year to year variation in corn hybrid digestibility due to growing
conditions from one year-to the next.

, Materials and Methods

Animals, diets, and experimental design were approved by Michigan State University
All University Committee for Animal Use and Care. The same eight cannulated barrows,
as described by Andersen (2001), were used to determine apparent ileal protein, true
protein, and ileal starch digestibility (Year 2) coefficients of the seven corn hybrids: high-
oil (HO), high-oil paired normal (HOPN), waxy (WX), waxy paired normal (WXPN),
high-lysine (HL), high-lysine paired normal (HLPN), and a normal yellow dent corn
(NYD). Year 2 data was obtained from feeding seven “nutrient-dense” com hybrids
(Andersen, 2001) that were harvested in 1997. Data for Year 1 (the same corn hybrids as
in Year 1, but harvested in 1996) starch digestibility was obtained from a consecutive 4 x
4 Latin square design in which the seven corn hybrids were fed to four ileally cannulated

barrows and the NYD hybrid was used in each square to make cross comparisons.

50

Furthermore, the seven corn treatments fed to the two groups of barrows were used to
investigate the relationship between ileal starch digestibility and the following: apparent
protein, true protein, and standardized ileal indispensable amino acid digestibility (SIID)
coefficients. The diets, feed intake, and environmental conditions were the same as
described by Andersen (2001). The experimental design was also the same as described
by Andersen (2001); however, during each digesta collection ((1 6 and 7), two fecal grab
samples were also collected from each pig for each 12 hr digesta collection.
Sample Preparation and analysis

Collected digesta and fecal samples from each pig were homogenized and pooled over
the 2-day collection and stored at -20°C until samples were prepared for further analysis.
Digesta samples were thawed, freeze-dried, and finely ground through a cyclone mill
(Cyclotec Sample Mill 1093,.Tec’ator Co, Hoganas, Sweden) for dry matter (DM), crude
protein (CP), amino acid (AA), starch and chromium analysis. Fecal samples were
freeze-dried and finely ground through a 1 mm screen using a cyclone mill (Cyclotec
Sample Mill 1093, Tecator Co., Hoganas, Sweden) for dry matter, chromium, and starch
analysis. Dry matter content of corns, diets, digesta, and fecal matter was determined
using a vacuum oven at 60°C for 16 h. Crude protein content of the respective corn
treatments and digesta was determined using an automated LECO® elemental analysis
istrument (AOAC # 990.03, crude protein and animal feeds; LECO‘1D FP-2000; LECO
Co., St. Joseph, MI). Amino acid determination of diets and digesta and chromium
analysis of diets, digesta, and fecal matter were analyzed according to procedures

described by Andersen (2001).

51

Starch concentration of digesta samples were determined using the following method.
A 0.2 g sample was placed in a 100 mL beaker and dispensed in 20 mL of ddH20. While
each beaker was swirled, 0.5 mL of 50% sodium hydroxide was added and allowed to
gelatinize for 15 min. The alkali solution was then neutralized with 15 mL of dngO, 10
mL of acetate buffer (2 M, pH 4.9), and 0.8 mL of concentrated hydrochloric acid. After
the addition of an amylase enzyme (Optidex L-300, Bio-cat Co.), each beaker was sealed
in aluminum foil and placed in a 55°C water bath for 16 h. The beakers were then cooled
and brought up to volume with ddeO in 200 mL volumetric flasks. Standard glucose
solutions containing 0, 10, 20, 30, 40, and 50 mg of D-glucose per 100 mL ddH20 were
prepared. Aliquots of glucose standards and samples (20 11L) were then transferred into
microplate wells. A 250 1.1L glucose oxidase-peroxidase (GOP) reagent was added to each
well. Wells were covered with tin foil to remove any sunlight and were allowed to remain
at room temperature for 60 i 5 min. The glucose absorbance of the samples were read
and starch content (%) in samples calculated.

Fecal starch analysis followed the same procedure as above with the modification that
Crystalzyme 40L was used instead of the Optidex L-300 enzyme. Tin foil insulation time
followed the GOP addition, but was reduced to 18 :1: 5 min (required time for
Crystalzyme 40L enzyme) before reading the glucose absorbance.

Statistical analysis

Data on protein digestibility (Year 2) was analyzed using the General Linear Model
procedure of SAS (1998) for a Latin square design. A linear model with main effects of
period, diet, and pig as a random variable were used to test the dependent variables:

apparent and true protein digestibility. Three orthogonal and three non-orthogonal

52

contrasts were used to determine differences between the following pre-planned
comparisons: HO vs. HOPN, WX vs. WXPN, HL vs. HLPN, HO vs. the four control
corns (HOPN, WXPN, HLPN, and NYD), WX vs. the four control corns, and HL vs. the
four control corns at one level of significance, P < .05.

The MIXED procedure of SAS (1998) was employed for ileal starch digestibility for
both Year 1 and 2. A linear model with main effects of square, collection nested within
square, diet, and pig as a random variable were used to test the dependent variable: Year
1 ileal starch digestibility. Data for Year 2 starch digestibility was obtained from a
complete 8 x 8 Latin square design. A linear model with main effects of period, diet, and
pig as a random variable were used to test the dependent variable: Year 2 ileal starch
digestibility. Orthogonal and non-orthogonal contrasts were used to determine differences
between the means of the same pre-planned comparisons as described above.

The relationship between. ileal starch digestibility and apparent protein, true protein,
and standardized indispensable ileal amino acid digestibility values were determined
using the General Linear Model and Regression procedures of SAS (1998) in order to
obtain the slope, intercept, and R-squared values of the various relationships investigated
above. Also, the relationship between fecal starch digestibility and standardized
indispensable ileal amino acid digestibility was tested following the procedure described
above.

Results

Apparent and true protein digestibility values are reported in Table 12. No differences
were observed between the pre-planned comparison, HO vs. HOPN, WX vs. WXPN, HO

vs. the four control corns (HOPN, WXPN, HLPN, and NYD), WX vs. the four control

corns, and HL vs. the four control coms for apparent and true protein digestibility.

53

However, apparent and true protein digestibility was greater in the HLPN (P < .05) com
as compared to the HL corn hybrid.

Ileal starch digestibilities are reported in Table 13. Year 1 ileal starch digestibilities
ranged from 79.56 to 92.50 %. Year 2 ileal starch digestibilities were numerically higher
than Year 1 digestibilities and ranged from 88.03 to 94.71 %. For Year 2, HO and HL
were higher (P < .05) than the four control corns for ileal starch digestibility. In addition,
HL was greater (P < .05) than HLPN for Year 2 ileal starch digestibility. Fecal starch
digestibilities for Year 2 (Table 13) ranged from 95.46 to 99.18 % with an average of
97.28 %. Fecal starch digestibility for HL was higher (P < .05) HLPN and the four
control corns.

In the present study, apparent and true protein digestibility from Year 2 was shown to
be positively (r = .175 - .176, P < .05) related to ileal starch digestibility (Figure 1 and 2)
for the specialty corn hybrids. The mean digestibility values of the corn hybrids (Figures
3 to 10) were compared to the mean ileal starch digestibility values. No significantly
positive correlation (P < .05) was found to exist between ileal starch and indispensable
ileal amino acid digestibility values; however, there was a positive correlation trend (r =
.272 - .274, P < .07) for histidine and phenylalanine. Correlation coefficients were .179,
133,. .054, .035, .243, and .096 for Lys, Val, Ile, Leu, Arg, and Thr respectively.
However, no relationship existed between fecal starch and standardized indispensable
amino acid digestibility.

Discussion
The apparent protein digestibility value for the Year 2 HO corn hybrid was lower than

the value of 87.1 % reported by Risley et al. (1996); however, differences are probably

54

due to the fact that Risley (1996) fed a complete com-soybean meal diet to weanling pigs,
whereas we fed a deficient diet. The apparent protein digestibility value for the WX corn
at 61.36 % was lower than the value (68.48 %) reported by Soltwedel (1994). No
published values are available for tme protein digestibilities for the WX corn hybrids. In
addition, no published values are available for apparent and true protein digestibility of
the HL corn hybrids.

In a review of digestion and absorption of carbohydrates, Rerat (1978) commented
that starch constitutes the major part of usual diets for non-ruminants and its digestibility
is around 100% in rats and mice for cereal starches. However, recent in vitro studies
conducted by Cone and Vlot (1990) suggest that enzymic digestion of starch in the small
intestine is incomplete.

Several studies have been conducted in ruminants to determine starch digestibility of
various feedstuffs (Owens et al.. 1986; Rooney and Pflugfelder, 1986; Cone and Vlot,
1989); however, few studies have assessed starch digestibility of various feedstuffs in
growing pig. No studies have assessed the ileal starch digestibility of various specialty
corn hybrids in growing pigs. The present study determined the ileal digestibilities of
HO, HL, and WX corn hybrids. The average ileal starch digestibilities of HO, HL, and
WX corn diets (Year 1 and 2 compiled) were 89.83, 91.33, and 93.61 %, respectively. In
maize and pea starch, Everts et al. (1996) reported ileal starch digestibility values of 98.3
and 97.5% in 30 kg pigs. In terms of ileal starch digestibility, our values were lower than
values reported by Everts et al. (1996). Differences in results may be due to the fact that
each study used different size and age of pigs, and employed different methods to

determine ileal starch digestibility. Rerat (1978) concluded that ileal starch digestibility

55

does not always equal 100% and is often related to the age of the animal, the source of
starch (Graham et al., 1989), and the processing of starch (Rerat, 1978; Graham et al.,
1989)

Also, no studies have assessed the fecal starch digestibility of various specialty corn
hybrids fed to growing pigs. The highest fecal digestibility in the present study was the
HL diet at 99.18%. Fecal starch digestibilities for maize and pea starch were 99.0 %
(Everts et al., 1996). Lin et al. (1987) and Sauer et al. (1977) reported fecal starch
digestibility values of 100 and 98.2 % for growing pigs fed corn as a sole source of
protein and energy. Cunningham (1959) also reported a fecal starch digestibility value of
76 % for soluble starch in 25 day-old pigs. The fecal starch digestibility in the present
study varied between 95.46 and 99.18 %. Thus, our reported values for fecal starch
digestibility are comparable to other published values (Sauer et al., 1977; Lin et al., 1987;
Everts et al., 1996).

According to Johnston (1991) the unique properties of waxy cornstarch can be
attributed to the fact that nearly 100 % of the starch in waxy corn is amylopectin, which
is assumed to be more digested within the animal than amylose. However, in the present
study the waxy corn did not have the highest ileal and fecal starch digestibility values as
was expected, suggesting that the amylopectin starch was not as readily available to the
animal as we had previously thought.

No studies have assessed the effect of apparent protein, true protein and standardized
ileal amino acid digestibility on ileal starch digestion in non-ruminants. However,
Philippeau et al. (2000) conducted a study to investigate the influence of endosperm

protein distribution in dent and flint corns on ruminal starch digestion. The results

56

showed that ruminal starch degradablility was negatively linked to the amount of zein
proteins (P < .05) and positively linked to the amount of glutelins (P < .05) for both dent
and flint corn. However, the flint corn was defined as being surrounded by protein
storage bodies and embedded in a dense matrix of endosperm cells (zein proteins),
whereas the dent corn endosperm had little cellular structures and the highest density of
starch granules and true glutelins. Thus, Philippeau et al. (2000) suggested that the dent
corn would induce an increase in the accessibility of starch granules to degradation in the
rumen as compared to the flint com- endosperm, due to increased glutelin composition.
Thus, their results suggest that the composition of maize endosperm may in fact affect
starch degradation within the rumen.

Our study showed that a positive relationship exists between apparent protein and true
protein digestibility and ileal starch digestibility. Whether this is related to cellular
structure and protein distribution within the endosperm as described by Philippeau et al.
(2000) is unknown. It could also be hypothesized that certain enzymes, activated by
specific amino acids and an acid environment in the duodenum, play an important role in
starch degradation.

The principal stimulant of enzymic secretions from the pancreatic acinar cells is
cholecystokinin (CCK), which in turn is released in response to the presence of amino
acids and fatty acids in the duodenum. The enzyme, or-amylase, is secreted by the
pancreatic acinar cells and is the enzyme responsible for degrading starch. The release of
(Jr-amylase is stimulated by CCK acting on the pancreatic acinar cells. Only L-isomer
forms of amino acids are effective in CCK release. Furthermore, phenylalanine and

tryptophan are potent releasers of CCK (Meyer et al., 1976). There is also strong

57

evidence that some peptides also release CCK. Three dipeptides, all of which contain
glycine (glycylphenylalanine, glycyltryptophan, and phenylalanylglycine), have been
proven to be strong releasers of CCK. Although we did not look at glycine’s relationship
with ileal starch digestibility, the indispensable amino acids, phenylalanine and histidine,
tended to be positively correlated to ileal starch digestibility. There is also some evidence
that some peptides containing at least four amino acids are also effective releasers of
CCK (Johnson, 1997). Furthermore, CCK is known to be active throughout the small
intestine, up to the ileum (Johnson, 1997).

In addition to CCK, secretin reduces the amount of acid in the duodenum by
stimulating the release of bicarbonate fi'om the pancreatic duct cells. The amino acid,
phenylalanine, and an acid environment stimulate the continuous release of secretin.
CCK and secretin potentiate each other for stimulation of release of bicarbonate and
pancreatic enzymes (Johnson, 1997).

The puzzling fact about this study is that the HL hybrid was found to have a lower true
protein digestibility than the HLPN corn, yet the HL hybrid had a higher ileal starch
digestibility than HLPN for both year 1 and 2. This may be due to the fact that protein
digestion and even protein content of the corn may be directly stimulating starch
digestion in the gut as mentioned above.

Implications
The present study provides apparent and true protein digestibility and ileal starch
digestibility coefficients for specialty corn hybrids, which are gaining popularity within
the swine industry as a replacement for normal dent com. This study showed that the

apparent and true protein digestibility in specialty corn hybrids were similar when

58

compared to normal dent corns. In addition, this study demonstrated that starch
degradation is not complete (~ 90 %) at the terminal ileum, regardless of what type of
corn is fed to growing pigs and that a definite relationship exists between starch and
protein digestibility. However, further research is warranted to identify the exact

relationship between starch degradability and specific amino acids present in growing

pigs.

59

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61

Figure 1: Relationship between apparent protein and ileal starch digestibility.
Y = 80.35 — 0.169X. r2 = 0 175,1) = .001.

Figure 2: Relationship between true protein and ileal starch digestibility.
Y = 79.56 — 0.143x. r2 = 0.176, P = .001.

62

 

 

42086420
99988888

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80

70

60

50

40

Apparent Protein Digestibility (%)

 

 

208642
998888

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110

100

90

80

70

60

50

40

True Protein Digestibility (%)

63

Figure 3: Relationship between standardized lysine and ileal starch digestibility.
Y = 73.45 — 0.2030112 = 0.179, P = .132.

64

'igestibility.

Ileal Starch Digestibility (%)

94 .

84-

82*

807

 

 

 

 

78

65 70 75 80 85 90 95

Standardized Lysine Digestibility (%)

 

0 Year 1 Lysine stear 1 Starch
0 Year 2 Lysine vs Year 2 Starch
-— Plot 1 Regr

 

 

 

65

Figure 4: Relationship between standardized valine and ileal starch digestiblity.
Y = 76.49 — 0.159x. r2 = 0.133, P = .109

66

Ileal Starch Digestibility (%)

 

 

 

T T 1

70 75 80 85

Standardized Valine Digestibility (%)

 

I Year 1 Valine vs Year 1 Starch
0 Year 2 Valine vs Year 2 Starch
— Plot 1 Regr

 

 

 

67

Figure 5: Relationship between isoleucine and ileal starch digestibility.
Y = 79.57 — 0.120x. r2 = 0.054, P = .422.

68

Ileal Starch Digestibility (%)

94

92-

88

86

82~

80‘

78

.1

A

.1

 

 

65

t I l ' I

70 75 80 85 90 95

Standardized Isoleucine Digestibility (%)

 

0 Year 1 Isoleucine vs Year 1 Starch

0 Year 2 Isoleucine vs Year 2 Starch

 

 

— Plot 1 Regr

 

69

 

Figure 6: Relationship between leucine and ileal starch digestibility.
Y = 79.69— 0.117x. r2 = 0.035, P = .522.

70

Ileal Starch Digestibility (%)

94~

92‘

88

86‘

82‘

80‘

78

 

 

 

 

O
C
.0 0.0 2.
'i W
C
C
65 70 75 80 85 90 95

Standardized Leucine Digestibility (%)

 

0 Year 1 Leucine vs Year 1 Starch
0 Year 2 Leucine vs Year 2 Starch
—— Plot 1 Regr

 

 

 

71

_.‘ - 3'...“ 3...: u- hm“-

 

Figure 7: Relationship between standardized arginine and ileal starch digestibility.
Y = 64.77 — 0.299x. r” = 0.243, P = .074.

72

Ileal Starch Digestibility (%)

82-

80

78

l

 

 

 

65

70

75 80 85 90

Standardized Arginine Digestibility (%)

 

 

OI Year 1 Arginine vs Year 1 Starch
0 Year 2 Arginine vs Year 2 Starch
—— Plot 1 Regr

 

 

73

95

100

' .9 him!“

 

Figure 8: Relationship between standardized histidine and ileal starch digestibility.
Y = 72.22 — 0.203x. r’ = 0.272, P = .056.

74

Ileal Starch Digestibility (%)

 

 

 

I I I I U

70 75 80 85 90

Standardized Histidine Digastibility (%)

 

1..

 

0 Year 1 I-listidine vs Year 1 Starch
0 Year 2 Histidine vs Year 2 Starch
— Plotl Regr

 

 

 

75

Figure 9: Relationship between standardized phenylalanine and ileal starch digestibility.
Y = 64.73 — 0.299x. r2 = 0.274, P = .055.

76

 

1 d1geszir

Ileal Starch Digestibility (%)

 

 

82 -

80 7 .

78 I I t r r I
65 70 75 80 85 90 95

Standardized Phenylalanine Digestibility (%)

 

0 Year 1 Phenylalanine vs Year 1 Starch

0 Year 2 Phenylalanine vs Year 2 Starch

 

 

— Plot 1 Regr

 

77

 

Figure 10: Relationship between standardzzed threonine and ileal starch digestibility.
Y = 82.06 — 0.093X. r = 0.096, P = .281.

78

Ileal Starch Digestibility (%)

96~

94‘

 

 

 

84 ~

82 .

80 1 .

78 I V fl T I
50 60 70 80 90 100

Standardized Threonine Digestibility (%)

 

0 Year 1 Threonine vs Year 1 Starch
0 Year 2 Threonine vs Year 2 Starch
Plot 1 Regr

 

 

 

 

79

 

CHAPTER 4: EFFECT OF NUTRIENT-DENSE CORN HYBRIDS FED TO
GROWING PIGS ON NITROGEN METABOLISM AND UTILIZATION

Abstract

Six crossbred barrows (41.30 i .49 kg, Yorkshire x Duroc) were used in a 6 x 6 Latin
square experimental design to determine the effects of feeding different nutrient-dense
com hybrids on nitrogen metabolism and utilization. The corn hybrids used were: high-
oil (HO), high-oil paired normal (HOPN), high-lysine (HL), waxy (WX), waxy paired
normal (WXPN), and a yellow dent corn (NYD). Pigs were fed a diet consisting of
96.85% of one of the respective test corn hybrids. Vitamins, minerals, dicalcium
phosphate, limestone, and salt were included at 3.15% of the diet to meet or exceed NRC
(1988) requirements. Pigs were allowed a 5-day adjustment period to the test diets,
followed by a 5-day total urine and fecal collection. Feces and urine were pooled at the
end of each 5-day collection and analyzed, forinitrogen content. Nitrogen intake was
greater for NYD (P < .05) than HL. However, nitrogen intake for HL was higher (P <
.05) than the average of the three control corns. Nitrogen excreted in urine was less in
WX and HL (P < .05) than their respective paired normal corns, WXPN and NYD. In
addition, N absorbed for WX and HL corn was less (P < .05) than their respective paired
normals, WXPN and NYD. However, nitrogen retained, nitrogen digestibility, and
nitrogen utilization was not different between HO vs HOPN, HL vs NYD, WX vs
WXPN, HO vs the average of the three control corn hybrids (HOPN, WXPN, NYD), HL
vs the average of the three control corn hybrids, and WX vs the average of the three

control corn hybrids (P > .05).

80

 

m 21. .2-

Introduction

Every year, more producers feed nutrient-dense corn hybrids to their livestock
(Bender and Hill, 2000). However, very little data is published on the nutritional value of
feeding these com hybrids to pigs. In the previous chapters, amino acid, protein, and ileal
starch digestibility was determined to provide digestibility coefficients for the following
corn hybrids: high-oil (HO), high-oil paired normal (HOPN), waxy (WX), waxy paired
normal (WXPN), high-lysine (HL), high-lysine paired normal (HLPN), and a yellow dent
corn (NYD). However, in order to fully understand the nutrient availability and
utilization of these corn hybrids, the nitrogen retention and utilization must be
investigated. Therefore, the objective of our research was to evaluate the N retention,
digestibility, and utilization of high-oil, high-lysine, waxy, and their respective paired
normal corn hybrids in groWing pigs.

Materials and Methods

All animals and experimental protocols were approved by Michigan State University
All University Committee for Animal Use and Care. Six crossbred barrows (Yorkshire x
Duroc) with an initial body weight of 41.3 i .5 kg were used to determine nitrogen
retention, digestion, and utilization of six corn hybrids: high oil (HO), high oil paired
normal (HOPN), waxy (WX), waxy paired normal (WXPN), high lysine (HL), and a
normal yellow dent corn (NYD). The HLPN hybrid that was used by Andersen (2001)
became rancid and was tested positive for vomitoxins (4.8 ppm); therefore, it was not
used in this study. Pigs were randomly assigned to treatments, which consisted of one of
the test corn hybrids. The treatment assignments were the same as described by Andersen

(2001). The respective test corn hybrids provided the only source of protein and energy at

81

 

96.85% of the total diet. Vitamins, minerals, dicalcium phosphate, limestone, and salt
were included to meet or exceed NRC(1998) requirements.

The six barrows were randomly assigned to one of the six experimental corn diets and
arranged in a 6 x 6 Latin square. Environmental temperatures ranged from 21.] to 330°C
with a mean temperature of 257°C. Pigs were individually housed in stainless steel
metabolism cages (l.2 m x 0.75 m) containing low pressure nipple waters that allowed
free access to water. The metabolism cages allowed for separate collection of urine and
fecal matter.

Feed intake was adjusted to 4.5% of pig metabolic body weight and maintained at this
level throughout the trial. Pigs were fed equal meals twice daily and allowed a 5-day
adjustment period to the experimental diets. The diet adjustment period was followed by
five days of A separate fecal and urinary celleotion. During the 5-day adjustment period, an
amino acid top dress was applied to the test diets during the first four days as described
by Andersen (2001). Five grams of Ferric Oxide was mixed with 100 g of diet and used
as an indigestible marker to signal the initiation and termination of the fecal collection.
Feces and urine were collected once daily with weight and volume recorded. Urine was
preserved by the addition of 100 mL of 6 N hydrochloric acid to each daily collection.
Twenty percent of the daily urine samples were kept and pooled. At the end of the 5-day
collection, 20% of the total urine volume was kept and frozen at -20°C. Daily fecal
samples were also pooled and frozen at -20°C.

Chemical analysis

Fecal samples were thawed and homogenized in a Hobart mixer for 10 min and sub-
sampled. A 2 g sample was taken from the sub-sampled fecal matter and dried in a

vacuum oven for 16 h at 60°C for determination of dry matter content. The sub-sampled

82

 

fecal matter was freeze-dried and ground through a 1 mm screen using a cyclone mill
(Cyclotec Mill 1093, Tecator Co., Hoganas, Sweden). Diets, freeze-dried feces, and
liquid urine were analyzed for nitrogen content using an automated LECO® elemental
analysisistrument (AOAC # 990.03, crude protein and animal feeds) (LECOQ FP-ZOOO;
LECO Co., St. Joseph, MI).

Statistical analysis

Data was analyzed using the Mixed procedure of SAS (1998) in a Latin square design.
A linear model with main effects of period, diet, and pig were used in the statistical
model. Contrasts were used to determine differences between the following preplanned
comparisons: HO vs. HOPN, WX vs. WXPN, HI. vs. NYD, HO vs. the average of the
three control corn hybrids (HOPN, WXPN, and NYD), WX vs. the average of the three
control corn. hybrids, and HE: vs the average of the three control corn hybrids at one level
of significance (P < .05).

Results

The barrows had an average daily gain of 0.39 kg and an average daily feed intake of
2.08 kg. The chemically determined nutrient composition of the corn diets are shown in
Table 15. The main difference between these diets and the diets described by Andersen
(2001) is the exclusion of 0.25% chromic oxide. The nutrient composition of the corn
hybrids (Table 15) were reported by Andersen (2001). Nitrogen digestibility, N retention,
and DM digestibility are presented in Table 17. Nitrogen intake of the HL hybrid was
lower (P < .05) than NYD and the three control corn hybrids (HOPN, WXPN, and NYD).
Nitrogen in feces (g/d) was similar across all the experimental diets; however, NYD was
numerically higher (P > .05) than the other com hybrids. The N content in the urine for

WX and HL was lower (P < .05) than the N content in the three control corns. Also, the N

83

 

content in the urine for HL was lower (P < .05) as compared to its paired normal, NYD.
Nitrogen absorbed (g/d) in the WX and HI. hybrids was lower (P < .05) than for the three
control corn hybrids. In addition, the N absorbed in the HL hybrid was less (P < .05) than
as compared to its paired normal, NYD. No differences (P > .05) were detected across all
the contrast investigated for N retained, DM intake, fecal DM output, N retention as a
percent of intake and absorbed, and DM digestibility.

Discussion

Adeola and Bajjalieh (1997) conducted a study in 20 kg crossbred pigs to compare the
N utilization of three high-oil corn varieties to regular corn, when fed as the sole source
of protein and energy. The average N digestibility of the three high-oil corns was 76.3%.
The published values for N retention. as a percent of intake for the high-oil varieties
ranged from 47.3 to 55.3% and N retention as a percent of absorbed ranged from 62.2 to
72.4%. Snow et a1.'(1998} also conducted a N balance trial using 20 kg pigs, and reported
a high-oil corn N digestibility of 83.31 i 2.13%, a N retention as a percent of intake of
49.74 i 5.35%, and a N retention as a percent of absorbed of 59.73 i 6.52%. The N
digestibility and retention values published for high-oil corn in 20 kg pigs are higher than
our reported values for 40 kg pigs of 67.80 i 2.02% for N digestibility, 33.63 i 6.75%
retention as a percent of intake, and 49.19 i 9.61% retention as a percent of absorbed.
Furthermore, both Adeola and Bajjalieh (1997) and Snow et al. (1998) reported higher
ether extracts (%) for high oil corn as compared to the high-oil corn tested in the present
study. Our high-oil corn had a relatively low ether extract (3.52%). It is possible that

weather conditions at time of planting the seed and at time of harvesting may have

84

fl

_ ‘31)]!-

 

affected the oil content of our high-oil hybrid, which then may have contributed to the
low digestibility and utilization values that we obtained in the present study.

Asche et al. (1986) reported N utilization values of dry, high-moisture, and
reconstituted high-lysine corn diets in 35 kg pigs. The N digestibility values for the
various high-lysine corn diets ranged from 79.35 to 83.29%. Total N retained (g/d)
ranged from 11.46 to 13.06, and N retention as a percent of intake ranged from 42.92 to
45.84% for dry, high-moisture, and reconstituted high-lysine corn. Sachtleben (1975)
reported a high-moisture, high-lysine N retention as a percent of intake of 59.1 _+_ 3.3 %
and a N digestibility value of 82.9 i 1.6% in growing-finishing pigs. Snow et al. (1998)
also conducted a N balance with high-lysine corn and reported a N digestibility value of
81.06 i 2.13%, 57.22 i 5.35% nitrogen. retained as a percent of intake, and 70.75 i
6.52% nitrogen retained as a percent of absbrbed. The value for total N retained in high-
lysine corn (9.81 i- 205 g/d) in the.present study was comparable to Asche’s values for
total N retained. However, the values for N digestibility (72.58 i 2.02%), N retention as a
percent of intake (33.54 i 6.75%), and N retention as a percent of absorbed (43.58 i
9.61%) were lower than other published values (Sachtleben, 1975; Asche et al., 1986;
and Snow et al., 1998).

The only published values available for waxy corn to compare to this study came from
Sachtleben (1975). Sachtleben conducted a N balance on 25 kg pigs to determine the
value of high-moisture, waxy corn. diets on growing swine performance. Sachtleben
obtained a N retention as a percent of intake value of 68.5 i 3.3% and N retention as a

percent of absorbed value of 85.0 i 1.6%. Once again, the values reported in this study

for N retention as a percent of intake (30.77 i 6.75%) and N retention as a percent of

85

_ u. Jl- I '7.“1.\4 I ('1':-

 

absorbed (42.62 i 9.61%) for waxy corn diets were lower than published values reported
by Sachtleben (1975). Values for N digestibility and retention as a percent of intake and
as a percent of absorbed of normal yellow dent corn in the present study were 68.38 i
2.02%, 19.39 i 6.75%, and 24.22 i 9.61%, respectively. Our N digestibility and retention
values for normal dent corn were lower than other published values (Sachtleben, 1975;
Asche et al., 1986; Adeola and Bajjalieh, 1997; and Snow et al., 1998). These differences
may be due to the fact that our pigs were on a deficient diet compared to the studies
discussed above, where pigs were fed complete diets. However, Snow et a1. (1998) fed
corn as a single feed ingredient and found N digestibility and N utilization to be higher
than our reported values. Also, Snow et al. (1998) used 20 kg pigs as compared to 40 kg
pigs in the present study. Also, the deficient diets in the present study caused the pigs to
grow, retain N, and utilize N at a much iess efficient rate as compared to those on a
complete com-soybean meal diet. However, dry matter digestibility values in this study
ranged from 83.17 to 85.31%, which were within range of values reported by Asche
(1986), but slightly lower than values reported by Snow et a1. ( 1998) and Adeola and
Bajjalieh (1997), and slightly higher than values reported by Sachtleben (1975).

Nitrogen digestibility was similar across all the corn hybrids, except for the WX
hybrid, which tended to be lower (P s .10) as compared to the three control corns.
Interestingly, N retention as a percent of intake and absorbed was also similar across all
hybrids. However, the nutrient-dense hybrid performance of HO, WX, and HL was
inferior to previously published values (Sachtleben, 1975; Asche, 1986; Adeola and
Bajjalieh, 1997; and Snow et al., 1998). Reasons for the lower N digestibility and

utilization performance from the present study may be due to several factors: the poor

86

 

 

r“

weather conditions at time of planting and harvesting the corn hybrids (Jones and
Andersen, 1999), the time of year that the experiment was conducted, the size and age of
the pigs, the type of diet fed (completely balanced or deficient), and environmental
conditions in which the experiment was run.

Implications

The present study showed that feeding high-oil, waxy, and high-lysine hybrids to
growing pigs results in similar nitrogen retention and utilization. Therefore, feeding
nutrient-dense corn hybrids provides no nutritional advantage over most normal yellow

dent corn hybrids.

87

 

Fl,. ! A! H‘EELEV” find '

Table 14: Composition of experimental diets on as-fed basis (%)

 

 

 

 

Ingredients Experimental

Corna 96.85

Dicalcium phosphate 0. 50 P“ ‘"
Limestone 0.25

Vitamin premixb 0.30

P

Trace mineral premixc 1.25

Salt ' 0.85

 

‘ Corn varieties used were HO, HOPN, WX, WXPN, HL and NYD.

bProvided the following per kilogram of diet: 4,583 IU vitamin D3, 55 IU vitamin E, 11
mg vitamin K, 3.66 mg menadione, 0.0275 mg vitamin B12, 3.66 mg riboflavin, 14.67
mg d-pantothenic acid, 22 mg niacin, 0.913 mg thiamine, 0.825 mg pyridoxine.

“ Provided the following per kilogram of diet: 335 g Ca, 5 g Fe, 5 g Zn, 5 mg Cu, 5 mg
Mn, 150 ug Se and 75 pg 1.

88

Table 15: Nutrient Composition of corn varieties (dry matter basis)

 

Items HO HOPN WX WXPN HL NYD
Dry matter, % 86.35 85.73 84.97 85.85 86.45 86.12
Crude protein, % 7.09 6.88 7.31 7.33 7.97 8.34
Gross energy, Meal/kg 4.58 4.78 4.27 4.50 4.61 4.35
Ether Extract, % 3.52 5.54 4.24 4.01 4.50 4.00

Amino acids, %

Indispensable

Arg 0.43 0.41 0.40 0.39 0.53 0.40
His ,. 0.30 0.29 0.29 0.30 0.37 0.34
Ile . 0.23 1 0.24 . 0.26 0.23 0.26 0.33
Leu 0.74 .. 0.70 0.71 0.73 0.60 1.00
Lys 0.19 0.20 *‘ 0.21 0.21 0.30 0.20
Phe 0.32 0.31 0.32 0.32 0.31 0.42
Thr 0.23 0.27 0.26 0.24 0.26 0.31
Val 0.36 0.36 0.36 0.37 0.42 0.43

Dispensable
Ala 0.50 0.49 0.49 0.50 0.48 0.62
Asp 0.36 0.45 0.39 0.48 0.66 0.28
Glu 1.05 1.11 1.09 1.13 1.15 0.92
Gly 0.27 0.28 0.28 0.27 0.34 0.29
Pro 0.57 0.51 0.56 0.54 0.58 0.71
Ser 0.38 0.34 0.35 0.35 0.36 0.42
Tyr 0.27 0.27 0.28 0.28 0.30 0.31

ZAmino Acids 6.20 6.23 6.25 6.34 7.22 6.98

 

89

 

Table 16: Amino acid top dress compositionab (g/kg)

 

 

Amino acid HO HOPN WX WXPN HL NYD
Ile 1.86 1.76 1.65 1.80 1.63 .933
Leu — .150 — —— 1.06 _
Lys 6.89 6.71 6.57 6.57 5.48 6.66
Met .070 .160 .010 —- .120 .050
Phe 1.18 ' 1.34 ' 1.20 1.19 1.30 .160
Thr 2.82 2.43 2.49 2.70 2.46 1.96
Trp 1.70 1.70 1.70 1.70 1.70 1.70
Val 1.60 1.57 1.56 1.50 .983 .908

 

‘ Amino acid top dress = amino acid requirement (NRC, 1988) for 50 to 80
kg pigs — amino acid content in the corn varieties.
b Added back to the test diets to meet the amino acid requirements.

90

 

 

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91

SUWARY AND GENERAL CONCLUSION

The goal of this thesis was to investigate protein, amino acid, and starch digestibility
and the relationship between ileal starch and the following: protein and amino acid
digestibility of high-oil, high-oil paired normal, waxy, waxy paired normal, high-lysine,
high-lysine paired normal, and normal yellow dent corn in growing pigs.

Apparent and standardized amino acid digestibilities were determined for each of the
corn hybrids. The apparent amino acid digestibility of the high-oil and high-lysine paired
normals were superior to their hybrids, high-oil and high-lysine. Also, the high-oil hybrid
was inferior to the average of the four control corn hybrids for apparent amino acid
digestibility. A similar pattern was observed for standardized amino acid digestibility.
The high-oil and high-lysine paired normal corns were superior to the high-oil and high-
lysine hybrids for standardized amino acid digestibility. However, for both apparent and
standardized indispensable amino acid digestibility, no differences were observed for the
comparison of waxy vs. waxy paired normal and waxy vs. the average of the four control
corns.

In the second experiment, ileal starch digestion and the relationship between ileal
starch and protein and amino acid digestibility were investigated. The ileal starch
digestibility of high-oil and high-lysine was superior to the four control corns for Year 2.
Fecal starch digestibility (Year 2) for the high-lysine hybrid was superior to the high-
lysine paired normal and the four control corns. In addition, a positive, linear correlation

(r = .175 - .176, P < .05) was observed between ileal starch digestibility and apparent and

true protein digestibility.

92

p.“

 

fix.» ..- a :v
1

Nitrogen metabolism and utilization of the corn hybrids were investigated in the third
experiment. The results showed that nitrogen retained, dry matter digestibility, and
nitrogen as a percent of intake and absorbed were similar across all test corn diets.

In conclusion, this research suggests that the nutrient-dense corns provide similar
performances for ileal starch and amino acid digestibility and nitrogen utilization as
compare to the normal dent corns. Therefore, when formulating diets for nutrient-dense
hybrids, we can currently use normal yellow dent hybrid digestibility coefficients until a

more complete data set of nutrient-dense hybrid digestibility coefficients are available.

93

rpm...

 

“To. an. ~. .
I

.

|

l

VITA

Lara L. Andersen was born and raised in the Upper Peninsula of Michigan. As a child
she was interested in Arabian horses, and became an active competitor of long distance
endurance racing. She was a five-year member of the UP. Distance Riders Association
and was active in many livestock activities throughout high school. After graduating from
high school in 1993, she came to Michigan State University to pursue a career with
animals. Upon graduating with a Bachelors degree in Animal Science in December of
1997, she was granted the opportunity to change direction and pursue a Masters degree in

swine nutrition under the supervision of Dr. Nathalie L. Trottier.

94

 

APPENDICES

95

“u . fl~’&&.1J.AL...x i-V'

 

Appendix A

Qlculations for digestibility:

Apparent ileal digestibility (AID):
Adapted from Snow et al. (1998)

AID = (100 — [(AAd/ AAf) x (CRf/ CRd)] x 100

Where:

AAd = Amino acid concentration in the digesta
AAf = Amino acid concentration in the feed
CRf = Chromium in the feed

CRd = Chromium in the digesta

Endogenous amino acid losses (EAL):
Adapted fi'om Rademacher et al. (1999)

EAL = [AAd x (CRf/ CRd)]

Where:

EAL = Basal endogenous amino acid flow, mg/ kg DMI
AAd = Amino acid concentration in the digesta

CRf= Chromium in the feed

CRd = Chromium in the digesta

Standardized ileal digestibility (SID):
Adapted from Rademacher et al. (1999)

SH) = [AID + (EAL/ AAD] x 100
Where:
AID = Apparent ileal digestibility

EAL = Basal endogenous amino acid flow, mg/ kg DMI
AAf = Amino acid concentration in the feed

96

 

 

Appendix B

Apparent indispensable amino acid digestibility of corn hybrids based on growing pigs’
age in weeksat

 

 

Age in Week Week Week Week Week Week Week Week Pooled
weeks 14 15 16 17 18 19 20 21 SEMb

Arg 82.15c 80.68 78.80 76.73 72.98 77.71 74.13 71.65d 2.14 ”A
His 88.51 89.21 88.35 87.24 85.83 87.92 86.42 86.19 1.06 :
Ile 75.21 77.26c 75.49 72.26 68.09d 73.73 71.56 70.07 1.77 5
Leu 82.98 84.55c 83.27 80.41 78.03d 82.15 80.74 78.72 1.40 E ..
Lys 66.69 69.26 67.51 64.67 60.15 63.82 60.76 61.89 2.04 .
Phe 81.04 83.11c 81.67 80.03 76.66d 80.90 79.06 78.32 1.36

Thr 65.44 68.92 68.15 69.89 61.79 67.49 66.04 62.62 2.33

Val 75.96 77.96c 76.29 73.83 70.17d 75.02 72.47 71.73 1.65

 

 

 

 

" Values are least square means.
b Pooled SEM represents the square root of the mean standard error divided by n.
c‘d Means in rows with different superscripts are different (P < .05).

97

 

Appendix C

Apparent dispensable amino acid digestibility of corn hybrids based on growing pigs’ age

 

 

 

in weeksa

Age in Week Week Week Week Week Week Week Week Pooled

weeks 14 15 16 17 18 19 20 21 SEMb
Ala 76.90° 78.07° 76.12c 72.55 65.80d 72.59 71.77 70.39 1.83 I“
Asp 72.32 75.95 75.41 73.51 68.36 74.30 72.63 69.84 3.74 i
Glu 79.04 80.62° 79.11 77.53 72.63d 78.21 77.36 74.45 1.54 1
Gly 48.24 41.09 39.15 35.73 27.37 38.80 37.58 26.71 4.76 L
Pro 58.16c 17.59 13.14 -13.17d -3.53‘1l 12.66 2.74 -18.85d 14.15 '
Ser 75.11 76.93‘ 75.95 76.08 70.43 76.53 73.72 72.18 1.54
Tyr 82.28 84.06c 81.61 ' 79.30 76.22d 82.29 80.61 79.45 1.46

 

a Values are least square means.
b Pooled SEM represents the square root of the mean standard error divided by n.
°’d Means in rows with different superscripts are different (P < .05).

98

 

Appendix D

Standardized indispensable amino acid digestibility of corn hybrids based on growing
pigs’ age in weeks3

 

 

 

Age in Week Week Week Week Week Week Week Week Pooled
weeks 14 15 16 17 18 19 20 21 SEMb
Arg 93.43c 91.36 89.32 87.94 83.35 87.74 84.00 81.81d 2.23
His 92.78 93.15 92.33 91.39 89.75 91.68 90.14 89.99 1.08
Ile 84.25 85.296 83.87 80.75 76.44d 81.45 79.52 77.94 1.79
Leu 87.75 88.80c 87.56 84.95 82.54d 86.30 84.92 82.97 1.38
Lys 77.30 79.25 77.60 75.21 69.98 73.29 70.03 71.35 2.09
Phe 87.23 88.57 87.34 85.82 82.39 86.18 84.48 83.71 1.36
Thr 79.88 - 81.85 81.56 83.48 75.27 79.98 78.86 75.16 2.33
Val 84.37 85.60c 84.10 81.90 77.94d 82.35 79.83 79.14 1.67

. _' ‘0“. u 2.... 2.0: I": ivy:

 

 

L. __.

a Values are least square means.
b Pooled SEM represents the square root of the mean standard error divided by n.
°‘d Means in rows with different superscripts are different (P < .05).

99

 

Appendix E

Standardized dispensable amino acid digestibility of corn hybrids based on growing pigs’
age in weeks3

 

 

 

Age in Week Week Week Week Week Week Week Week Pooled
weeks 14 15 16 17 18 19 20 21 SEM”
,_
Ala 86.02c 86.18c 84.48c 81.13 74.27‘l 80.43 79.78 78.35 1.86
1.
Asp 79.18 83.04 82.09 80.97 74.96 80.89 78.74 76.42 3.73 ;
Glu 84.80 86.12c 84.48 83.31 78.10d 83.39 82.47 79.65 1.56
Gly 88.38“ 78.30 76.63 74.89 64.43d 74.12 72.78 62.34d 5.25 L
Pro 141.580 88.78 87.45 61.90d 72.08d 82.38 74.31d 49.12 14.98
Ser 85.32 86.15 85.32 85.80 79.84 85.32 82.64 81.20 1.55
Tyr 88.60 89.796 87.46 85.37 8208d 87.77 86.14 85.01 1.47

 

a Values are least square means.

b Pooled SEM represents the square root of the mean standard error divided by n.

“’d Means in rows with different superscripts are different (P < 05)-

lOO

 

LITERATURE CITED

101

 

 

 

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