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thesis entitled

COMPOSITION AND NUTRITIONAL QUALITY OF
MICHIGAN LOW TEST WEIGHT CORN (1992) WHEN
FED TO PIGS

presented by

PETER PAUL CIZMARIK

has been accepted towards fulfillment
of the requirements for

M.S. degreein ANIMAL SCIENCE

 

 

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COMPOSITION AND NUTRITIONAL QUALITY OF MICHIGAN LOW TEST
WEIGHT CORN (1992) WHEN FED TO PIGS

BY

Peter Paul Cizmarik

A THESIS
Submitted to
Michigan State university
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Animal Science

1994

ABSTRACT

COMPOSITION AND NUTRITIONAL QUALITY OF MICHIGAN LOW TEST
WEIGHT CORN (1992) WHEN FED TO PIGS

BY

Peter Paul Cizmarik

A cold growing season resulted in wet, low-test weight
corn at harvest in IMichigan in 1992. The nutritional
quality of this corn was evaluated. Forty-six corn samples
were obtained from different locations within the State of
Michigan and analyzed for dry matter, crude protein,
lysine, minerals and protein fractions. Secondly, corns of
four test weight (54 to 76 kg/hl) were fed to pigs in an
energy and nitrogen balance study.

Calcium, phosphorus, iron, zinc and selenium were all

within ranges for typical Michigan corn, while lysine (%
DM) varied from 0.2 to 0.27 and was positively related to
crude protein (Pa-0.03). Protein quality differed among

corns (P<.05) and was lowest (P<.01) for corn 62.
Metabolizable energy values increased linearly with
test weight (54-76 kg/hl); corns 62, 66 and 76 all had

higher (P<.01) metabolizable energy than corn 54. Apparent
nitrogen and dry matter digestibilities were highest for
corn 76. Both, protein quality and energy content was
somewhat higher for the highest test weight corn.
Nutritional quality of corn was not markedly lowered until
test weight fell below 55 kg/hl.

ACKNOWLEDGEMENTS

I would like to express my appreciation and gratitude
to the following people whose efforts have aided me in my
graduate program.and the preparation of this thesis.

Dr. W. G. Bergen, committee chairman, for the
opportunity to continue my education beyond the Bachelor’s
degree and for guidance in. my research ‘work and his
critical reading of this manuscript.

Drs. P. K. W. Ng, D. Rozeboom and D. R. Hawkins,
committee members, for their helpful guidance and interest
during my graduate programs

Dr. E. R. Miller, for his supervision in setting-up
the feeding/balance trial and generous hands-on help with
the experiment.

Mr. Al Snedegar, manager of Swine Research Facilities,
for the use of the facilities and animals.

My wife, Marta, for her help in preparing this thesis

and her understanding love.

ii

TABLE OF CONTENTS

2393
LIST OF TnLBSOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO0......O v
LIST OF FIMSOOOOOOOOOOOO ...... OOOOOOOOOOOOOOOOOOOOOO v1
100 ImODUCTIONOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO00...... 1
2.0 REVINOF LITEMWOOOOOOOOOOOOOOOOOOOOOOOO0....O 4
2.1 Amino Acids Composition and Protein
quality at comOOOOOOOOOOOOOOOOOOOOOO00...... 4
2.2 Nitrogen and Energy Balance, Test‘Weight
and Nutritional Values of Corn, DM, N
and Energy Digestibility..................... 11
2.3 Minerals in Corn............................. 17
2.4 Protein Fractions of Corn.................... 21
3.0 ”TERInSmmmonSOOOO...OOOOOOOOOOOOOOOOOOOOO. 28

3.1 Design....................................... 28
3.2 Collection of Samples........................ 31
3.3 Determination of Percent Protein and Nitrogen 31
3.4 Determination of Gross Energy................ 32
3.5 Determination of Lysine Composition.......... 32
3.6 Determination of Minerals...... ..... ......... 33

3.7 Determination of Protein Fractions.. ..... .... 33

iii

3.8 Calculations and Statistical Analyses........
RESMTSmDISCUSSIONOOOOO0.0.0.0....0.0.0.000...

4.1 Lysine, Crude Protein and Test weight
Distribution.................................

4.2 Energy and Nitrogen Balance Study............
4.3 Minerals.....................................
4.4 Protein Fractions................ ..... .......
SUMMARY........... ......... .......................

BIBLIOGMPMOOOOOOOOOOOO ...... OOOOOOOOOOOOOOOOOOOO

iv

34

36

36

49

64

67

73

7S

10

LIST OF TABLES

Title Page

Comparison of Energy Values and Digestibi-
lities from Several Sources................... 15

Comparison of Minerals Values from Several
source8000.0.00000000000000000000000.0.0.0...O 19

Comparison of Protein Fractions from Several
sourCBBOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOCOO... 24

Experimental Design of Metabolism.Trial....... 29
Composition of Experimental Diets............. 30

Distribution of Crude Protein, Lysine
and Test‘Weight of Corn by Counties........... 37

Distribution of Crude Protein and Lysine
Content in Corn Relative to Test Weight....... 39

The Effect of Test weight on Energy Balance
and Nitrogen Balance in Young Pigs............ 51

Distribution of the Minerals by Counties...... 65

Distribution of Pertinent Constituents in Corn 68

10

11

12

13

14

15

16

LIST OF FIGURES

Title
Corn Protein Fractions.........................
Lysine Content in Corn Protein Fractions.......
Distribution of Test weight by Counties... .....
Locations of Test weight Corns by Counties.....
Distribution of Crude Protein and Test Weight..
Regression Plot of Crude Protein vs.Test‘Weight
Distribution of Crude Protein and Lysine.......
Regression Plot of Crude Protein vs.Lysine.....
Distribution of Lysine and Test Weight... ......
Regression Plot of Lysine vs.Test Weight.......
Distribution of Crude Protein (%)..............
Digestible Energy (kcal/g).....................
Metabolizable Energy (kcal/g)..................
Distribution of Ingested Nitrogen (%)..........
Daily Absorbed Nitrogen (g).............. ..... .

Daily Retained Nitrogen (g)... ............ .....

vi

2393

22
23
40

41

45
46
47
48
50
52
54
55
57

58

LIST OF FIGURES (Cont'd) .

figure

17
18
19
2O
21
22

23

11:13 2393
Net Protein Utilization (%) .................... 59
Biological Value (%) ........................... 60
Apparent Digestibility of DM (%). ........... ... 61
Apparent Digestibility of GE (%) ............... 62
Apparent Digestibility of N (%) ................ 63
Corn Protein Fractions (As Categories) ......... 70
Corn Protein Fractions (As Percent of Corn).... 71

vii

1 . 0 INTRODUCTION

Livestock production is the single largest
agricultural sector in the United States. Sales of
livestock and livestock products in the US make up
approximately 50% of cash receipts of agricultural product
sales (Agricultural Outlook 1985). The importance of
livestock. production. in the United States agricultural
economy, as well as in the overall economy, is apparent. In
this connection, it must be recognized that roughly three-
fourths of the costs of producing livestock are feed costs.
A high percentage of our nation's grain production is
normally used for livestock feeding purposes. Of all the
grains commonly used in livestock and poultry diets in the
United States, corn is by far the most important crop,
because it is produced in a quantity substantially over
that needed for human food. The United States is the
world's leader in corn production; annual production
approaches 50% of the world total. Corn generally accounts
for about 80% of the total quantity of grain fed to
livestock and poultry in the united States (AACCH, 1987).

Corn is palatable, readily digested by humans and by

monogastric and ruminant animals, and is one of the best
sources of metabolizable energy (ME) among the grains. The
availability of corn and soybean meal, as economical
sources of energy and protein, has played a most important
role in the initial rapid growth and the sustained
development of US livestock and poultry production.
Initially, these livestock <production enterprises used
primarily by-product materials from the grain milling and
beverage industries. As the nutritional needs of farm
animals became better known and the demand for high
available energy balanced diets increased, ground corn
became a major feed ingredient. Although corn is low in
protein content, the high proportion of corn in livestock
diet makes corn a major source of protein for the livestock
industry. Corn may thus provide 20-50% of the total
protein present in many livestock diets. However, the
nutritional quality of corn protein is low, because of a
low lysine content coupled with marginal tryptophan and
threonine and a high leucine content.

The corn harvested in Michigan after the 1992 growing
season was not typical. The growing conditions were cold
and wet, particularly during the later part of the season.
Moisture concentrations in corn at typical harvest times
were higher than normal, suggesting that the maturity of

corn was not as advanced and requiring more artificial

drying of the crop. Another widespread observation was that
the test weight of 1992 Michigan corn was often well below
bench values. If the test weight is down, is the overall
nutritional value also reduced?

Two studies 'were developed to: (l)determine 'with
growing pigs dry matter, nitrogen and energy
digestibilities of four corn samples ranging in test weight
from 54, 62, 66 to 76 kg/hl; (2)detemine nitrogen and
energy balance, protein quality and ME values of four corn
samples; (3)determine lysine content of 46 corn samples;
(4)determine :minerals content of 46 corn. samples with
emphasis on Ca, P, Zn, Fe and Se; (5)detenmine correlation
between lysine and test weight, crude protein and test
weight, crude protein and lysine of 46 test weight corns;
(6)determine protein fractions of four test weight corns
with emphasis on prolamines (Zein), albumins-globulins and

glutelins.

2.0 LITERATURE REVIEW

2.1 Amino Acids Composition and Protein Quality of Corn

It has been well established that when swine are fed
diets that are deficient in protein they do not grow or
reproduce normally (Pond, 1973; Baker and Speer, 1983). It
is now clearly recognized, however, that it is not proteins
per se but their building blocks, amino acids (AA), that
are the essential nutrients. The quality of dietary protein
is determined by its amino acid content, by its
digestibility and availability of amino acids and the
essential amino acids profile in relationship to the
essential amino acids requirement profile; eg. the AA
balance required by the animal (Wang and Fuller, 1989).
Cantor and Young (1982) showed, that quite likely most of
the relatively high "protein requirements" of humans and
other animals may simply be a requirement for one or more
of the essential amino acids and that when all of the
essential amino acids are present in the diet at optimum
levels, the actual protein requirement may be considerably
lower than previously indicated. Young pigs gain weight at
nearly normal rates when fed diets containing no intact
protein, but containing appropriate mixtures of free amino

acids (Shelton et al., 1950; Season at al., 1951; Hertz et

al., 1952; Eggert et al., 1955). Furthermore, sows are able
to maintain a normal pregnancy during the last 84 days of
gestation when fed a diet that contains crystalline amino
acids as the sole source of nitrogen (Easter and Baker,
1976).

Some amino acids are essential dietary components in
certain situations, but not in others. Arginine is required
for the growth of young pigs (Southern and Baker, 1983),
but sows are able to synthesize arginine via the urea cycle
at a rate sufficient to meet their needs for postpubertal
growth and pregnancy (Easter at al., 1974,- Easter and
Baker, 1976). Histidine is required during pregnancy
(Easter and Baker, 1977), but does not seem to be a dietary
requirement for maintenance of adult swine (Baker et al.,
1966). Proline (non essential amino acid) is not a dietary
requirement for swine for most stages of their life cycle,
but very young pigs (1 to 5 kg) are apparently unable to
synthesize proline rapidly enough to meet their
requirements (Ball et al., 1986).

The requirement for the two sulfur amino acids
(methionine and cystine) is usually met by a mixture of
these amino acids. Cystine can be synthesized from
methionine (but not vice versa), and therefore, methionine
can meet the total need for sulfur amino acids. Cystine can

satisfy at least 50% of the sulfur amino acid requirement

(Shelton et al., 1951b; Becker et al., 1955; Mitchell et
al., 1968; Baker et al., 1969b).

Phenylalanine can be converted to tyrosine, but not
vice versa. Tyrosine can satisfy at least 50% of the total
aromatic amino acid requirement (sum of tyrosine and
phenylalanine) . (Robbins and Baker, 1977) .

It has been established that the nutritional value
(quality) of a protein is primarily dependent on its amino
acid composition, especially the content and balance of
essential amino acids. With more knowledge about the amino
acid composition of proteins and the amino acid
requirements of swine, the emphasis has moved toward
assessing how well proteins and mixtures of proteins meet
amino acid requirements. A protein that contains a perfect
balance of amino acids, both among the essential amino
acids and between essential and nonessential amino acids,
has been defined as an ideal protein (Cole, 1979;ARC,1981).

Cereal grains, mostly corn or barley, form the basis
of most swine diets throughout the world and generally
supply 40% to 50% of the protein in the diets of growing-
finishing pigs. The amino acids in corn have generally been
found to be more available than in other grains (Eggum,
1973a). This grain, however, contains a relatively low
protein level, which also has an unbalanced pattern of

essential amino acids. Several experiments with swine at

various stages of growth have demonstrated that lysine

(lst) and tryptophan (2nd) are about equally limiting in
corn for growing pigs (Clawson and Matrone, 1963; Cromwell
et al., 1967; Gallo and Pond, 1968; Baker et al., 1969;
Ilori and Conrad, 1977; Lewis et al., 1979). Bressani et
al. (1962) stated that tryptophan and lysine showed varietal
differences at each of the four localities where corn was
grown. Usually, the nutritional value of corn and its
protein can be related directly to the lysine content of
the kernel and is governed by its digestibility, balance
and content of indispensable amino acids. According to
Arnold et al. (1977), lysine content on dry weight basis
increases as the total nitrogen content increases. Pass et

al.(l969) found a significant correlation between N

(varying from 1.6 to 2.6%) and lysine in grain of 48
selected strains of corn. Davis et al.(1970) analyzed 114
samples of inbred corns that contained the same N range and
found significant relationships among AA concentrations (as
percent of dry matter or as percent of protein). Keeney

(1970) investigated corn AA content in lower N corns (from

1.04 to 1.57%). He confirmed that the level of almost all
essential AAs was highest in the grain having the highest
N. Also, Miller et al.(1950) observed high correlations
between protein content, lysine and tryptophan, but were
unable to detect any differences in the distribution of
these amino acids between high- and low-protein corn. In
experiments with rats, Lewis et al.(1982) found that
threonine and isoleucine were the third and fourth limiting

amino acids in corn. In terms of supporting nitrogen

retention in young gravid gilts, corn is first-limiting in
lysine and second-limiting in tryptophan (Allee and Baker,
1970). After lysine and tryptophan, threonine is next in
importance, and is third-limiting in corn (Grosbach et al.,
1985). Several authors reported similar sequence of lysine,
tryptophan and threonine in corn. Asche et al.(1985),
Cromwell et a1. (1967), and Burgoon et al.(1992) reported

0.28%, 0.24% and 0.31% of lysine, 0.09%, 0.09% and 0.05%

of tryptophan and 0.33%, 0.32% and 0.35% of threonine
respectively. On the other hand, the proteins in corn have
a relatively high percentage of methionine and cystine.
However, Adeola et al.(1986) state that the digestibility
of protein is meaningful only if all the associated amino
acids are similarly available. Interestingly, there are
data that suggest that a decrease in dietary protein may
reduce the lysine requirement of swine for maintenance when
all other amino acids are adequate, however, pigs grow much
slower (Klay, 1964a,b; Baker et al., 1975; Lunchick et: al.,
1978; Easter and Baker, 1980).

The current National Research Council recommends that
feed for growing pigs(20.4-49.8kg)contains at least 0.48%
threonine. However, Friesen et a1. (1992) found that the

threonine requirement is higher and concluded that the

growing pig requires a dietary threonine concentration of

approximately 0.50%-0.60% (lO-llg per day) to optimize
growth performance. In another study Friesen et: al.(l992)
demonstrated that high lean growth gilts require at least
21-22g per day of total lysine for optimal average daily

gain, feed efficiency, and protein accretion rate. Tanksley
et al.(1987) showed that the contribution of corn in

meeting requirements for lysine was 27%, for tryptophan

33% and for threonine 49%.

Rivera et al.(1978) demonstrated that none of the
differences in protein quality for rats or pigs, or in
availability of Amino Acids (AA) and True Nitrogen
Digestibility(TND) for pigs due to stage of maturity or
drying temperature, were significant for corn. However, a
trend for better gains and feed conversion by pigs fed the

immature corn compared to those fed mature corn was
observed. Also, drying high-moisture corn at 40°C resulted

in higher AA availabilities and TND than drying at 60°C.

The reverse was true for low-moisture corn which showed
higher AA availabilities and TND from drying at 60°C vs. at

40°C. It appeared that high-moisture corn is more
susceptible to protein damage due to heat treatment than
low-moisture corn.

The protein content of corn grain is relatively high
during early maturation and decreases as full maturity is
reached (Sayre, 1948; Kiesselbach, 1950; Chandler, 1960).
Not only is the protein content of corn higher at early
stages of maturity, but also its amino acid profile seems
to be of higher quality.

Bressani and Conde (1961) followed the changes of
several amino acids in the corn kernel at nine stages of

maturity and found appreciable reductions in the content of

10

lysine, methionine, tyrosine and tryptophan in contrast to
increases in leucine as corn approached maturity.

Corn protein composition, and its amino acid ratios,
may vary widely due to genetic manipulation by plant
breeders, and to a lesser degree, by crop year (Earle,
1977) , soil fertility, crop management (nitrogen
fertilization), and climatic conditions (Hamilton et
al.,1951; Bird and Olson, 1972; Pierre et al.,l977; Asghari
and Hanson, 1984). Application of fertilizer to normal dent
corn can increase the total protein content to about 11.5%,

but growing corn depleted of nitrogen can produce kernels

with as low as 6% protein (Pierre et al., 1977). According
to Hamilton et al.(l951), Schneider et al.(l953), Pierre et
al.(1977), protein content is influenced by the available
soil nitrogen and by genetics of the plant (Alexander and
Creech, 1977; Pollner et al., 1979). Dudley et al.(1974)

have shown that the total protein content of corn can vary

from 4.4 to 26.6% by selection for protein content without
regard to grain yield. Differences in kernel protein and
yield response to soil nitrogen levels may also be
influenced by genetic differences in the capacity of
genotypes to take up nitrogen from the soil and translocate
the N as protein in kernels (Pollner et al., 1979).
Nitrogen availability to the plant can also be reduced by
competition from weeds and by drought. Most changes in
protein content of corn are due to changes in the amountof
endosperm proteins, mainly zein (Hamilton et al., 1951),

relative to the total protein present in the kernel.

11

2.2 Nitrogen and Energy Balance, Test Weight and Nutritio-
nal Values of Corn, DM, N and Energy Digestibility

Increasing grain moisture content (MC) affects test

weight values and energy density of corn negatively. Nelson
(1980) showed that test weight of corn at 10% MC was 74

kg/hl, while at 25% MC it was 69 kg/hl. As for trading
practices, Hill (1982b) proposed a more accurate practice

that reflects the actual dry matter in a lot of grain. He
proposed to retain 15.5% MC as the basis for trading. At

this moisture level, dry matter content is 84.5% and one
56 lb (25.4 kg) bushel of corn contains 47.32 lb (21.5 kg)
of dry matter. This is defined as a “standard bushel".

The most widely used measure of density in the
commercial US grain market is the so called test weight, a
measure of bulk density obtained by weighing a specific
volume of the grain. Measurement of test weight is
important in storing and transporting corn because it
determines the size of container required for a given lot
of corn. In the United States, test weight is measured in
pounds per bushel, but in the metric system, it is measured
in kilograms per hectoliter. The minimum test weight for US
Grade No.1 corn is 56 lb/bu (1 bu-0.3524 hl), which is
72.08 kg/hl. According to Hall and Hill (1974), test weight
changes during drying. These authors state that the amount
of increase in test weight during drying is affected by:

(a) initial moisture content of corn, (b) amount of kernel

12

damage, (c)drying temperature, (d) final moisture content,
and (e)variety. Most users of corn have commonly assumed
that test weight is a measure of the maturity or plumpness
of kernels, but the data of Hall and Hill (1973, 1974)
bring this assumption into question. Dorsebeedding et al.
(1991) found a low positive correlation between test‘weight
and protein (0.15-0.20) and a medium positive correlation
between density and protein (0.33-0.39). This observation
supports the conclusion that test weight is a poor
indicator of grain quality (Feeman, 1973).

It is true that corn harvested before maturity is low
in test weight. Maturity in corn is defined as the
cessation of dry weight accumulation by the kernels and is
identified as attainment of maximum moisture-free weight
per thousand kernels and, therefore, maximum yield (Frey,
1981). Maturation is also associated with gradual loss of
moisture (Hallauer and Russell, 1966; Schmidt and Hallauer,
1966) and with changes in density and test weight (Hill,
1975;.Nelson, 1980). As Shaw (1977) pointed out, the proper
maturation of corn is affected more by temperature in the
last two weeks of August and most of September, than by
rainfall, except in very dry weeks. Prolonged periods of
cloudiness, alone or combined with abnormally low
temperatures, can slow the corn maturation process; this
occurred in some parts of the North American Corn Belt in
1967, 1972, 1974, and also in 1992. At the other extreme,
moisture stress and high temperatures during the grain-

filling period can reduce the maturation rate.

13

Earle (1977) summarized the data on influence of
temperature and rainfall on protein and yield levels from
1907 to 1972. There is a negative correlation between
yields and protein content. Data show clearly that
increased yields, which started in early nineteen-thirties,
resulted in relatively lower grain protein; however,
increased fertilizer usage on corn has apparently been
enough to maintain protein levels as yields kept
increasing. Temperature and rainfall had generally positive
correlations to protein content and yields, but only
moderate increase of temperature and rather lower rainfall,
especially in July, favored higher protein levels and
yields (Earle, 1977).

Hicks (1975) reported that corn with a test weight of

40 lb/bu (51.4 kg/hl) has only 93% of the total digestible
nutrients of corn with 56 lb/bu (72.0 kg/hl) test weight.
He showed that a standard discount schedule of one cent
(1975 5 value) per bushel fairly discounts this loss in
value. But graduated discount schedules that deduct five
cents per bushel for test weights under 50 lb/bu (64.3
kg/hl) depart widely from the loss in actual value. Hill
(1975) reported that three sets of compositional and
feeding data show that corn with a test weight of 59.0-76.0
kg/hl (46-59 lb/bu) was satisfactory for swine. For sheep,
similar feeding results were obtained by Thornton et
al.(l969). Corn of 45 kg/hl (35 lb/bu) had a lower feeding
value, but even the standard discount schedule

overpenalized the low test weight corn (Hill, 1975). Lesson

l4

and Summers ( 1975) reported that test weight of immature
corn showed a positive correlation with metabolizable
energy for poultry (broilers) but a negative correlation

with protein and sugar content. Studies on metabolizable

energy (ME) of corn harvested from 53% to 31% moisture

also showed that ME values of imature corn decrease by

some 12 kcal/kg for each 1% increase in moisture at
harvest when fed to poultry (Leeson and Summers, 1976;
Lesson et al., 1977). Relationships between test weight and
animal feeding results are not consistent, probably because
of the influence of other contributing factors relating to
the causes of the test weight reduction and the differences
in corn composition.

Early studies of energy metabolism of swine were
reported by Capstick and Wood (1922), Deighton (1923,
1929), Brierem (1936, 1939) and Brody (1945). NRC (1964)
and ARC (1967) adopted the expression of energy
requirements of swine in terms of digestible or
metabolizable energy. Digestible energy (DE) is the energy
of the food consumed less the gross energy of the feces.
Digestible energy for pigs is correlated with the presence
of fiber in feed ingredients because of the limited ability
of the pig to digest cellulose and related compounds.
Metabolizable energy (ME) is the digestible energy consumed
less the energy lost in urine and combustible gases. The
energy lost in urine is the energy from nonutilized
absorbed compounds and end products of metabolic processes

associated with protein metabolism (1 . e. , urea) .

15

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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l6

Combustible gases are generally less than 2% of Gross
Energy intake in swine (Bowland et al., 1970; Just, 1982)
and are frequently not measured or considered in ME
evaluations. Recovered energy (RE), net energy for gain
(NEg) or energy balance is the feed energy retained as part
of the body or voided as a useful product, and in growing
animals is equivalent to tissue energy gain. Digestible
energy values are easily determined and have been reported
for a variety of feed ingredients. However, metabolizable
energy' provides :more constant estimate than. DE of the
energy value of feeds. The ratio of ME to DE ranges from
0.90 to 0.98 and ME decreases with increasing protein level
in corn (Asplund and Harris, 1969; May and Bell, 1971;
.Morgan et al., 1975).

Energy values of corn were investigated in numerous
balance experiments in the past and are summarized in the
Table 1. along ‘with dry’ matter, nitrogen and energy
digestibility, net protein utilization and biological

values .

17

2.3 Minerals in Corn

Corn germ is rich in mineral elements (ash); it
contains 78% of the kernel minerals, probably because they
are essential for early growth of the embryo. Corn, like
other cereal grains, is very low in calcium. The phosphorus
content of corn is also low but is about equal to that in
the' other common cereals and represents the most abundant
inorganic component in corn. It is largely present as the
potassium-magnesium salt of phytic acid, the hexaphosphate
ester of inositol. Phytin is an important storage form of
phosphorus (Hamilton et al., 1951; O’Dell et al., 1972),
which is liberated by phytase enzymes to initiate embryo
development. The germ of corn contains nearly 90% of the
phytate present in whole corn. For monogastric animals, it
is reasonable to assume that only 30% of the total
available phosphorus present is utilizable by this class of
animals. The presence of phytic acid interferes with the
availability of certain minerals, especially calcium, zinc,
and iron (Underwood, 1962; Momcilovic and Stahl, 1976).

The trace mineral content of corn is low compared to
that in small grains. In addition to supplying supplemental
sources of the macrominerals in a corn-soymeal diet, it is

advisable to include supplemental sources of the trace

18

minerals, including zinc, selenium, iron, manganese,
copper, and iodine, to prevent deficiencies (NRC, 1988).

Wolnik et al.( 1983) showed in their work that values
of most major elements such as Ca and P fall within a
fairly narrow range, while trace element compositions are
much more variable in corn. Although the absolute
concentrations of the elements may vary from sample to
sample, crop cultivars display distinct patterns of
relative elemental abundance even when grown over wide
geographical areas. The general pattern for the major
elements was P > Ca. Levels of Ca and P are deficient and
the bioavailability of P is low in corn, therefore, they
must be supplemented to grain-soybean meal diets for pigs
to perform at an optimal level. Studies by Bethke et
al.(1929) and by Wilgus (1931) showed that the diet must
contain not only minimum levels but also an optimum ratio
of calcium to phosphorus. A ratio of 1:1 to 1.5:1 is
generally considered to be within an acceptable range (NRC,
1988).

While minor elements display more variation, certain
predominant patterns are still apparent. The general
pattern for minor elements was Zn > Fe > Se. However, corn
grown in North Dakota is an important source of the
essential element selenium (0.01-1.00ppm) for animal

rations with biological availability of 83% (Scott, 1973),

19

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20

unlike Michigan corn, which is deficient in selenium
(wetson and Ramstad, 1987).

The elements that often showed the most normal
distribution were generally those with a relatively narrow
range between minimum and maximum values. This limited
normal distribution indicates that crop genetic factors are
more important than fertility, soil, and environment
(Chaney, 1983). Minerals values from several sources are

presented in Table 2.

21

2.4 Protein Fractions of Corn

Corn is often considered only as a major source of
calories, mostly derived from its high starch content. Yet
the sheer bulk of corn consumed as animal feed or human
food makes it essential to consider the protein supplied
with the calories. However, corn protein is made up of
several different types of subfractions which show
significant differences in protein and lysine content
(Figure 1.and Figure 2.). The original protein classes are
albumins (water-soluble), globulins (salt-soluble), zein or
prolamin (aqueous alcohol-soluble), glutelins. and residue
(not soluble in wmter, saline solutions or aqueous
alcohol), with the glutelins being the proteins extracted
by dilute alkali or acid (Osborne, 1907). A comparison of
corn protein fractions from.several sources are reported in
Table 3.

As early as eighty years ago, Osborne and Mendel
(1914) were able to conclude that zein was the protein that
limited the ability of corn to supply nutritionally
essential amino acids and that substitution of other corn
proteins for zein would improve the nutritional value of
corn, in other words, replacement of zein by other corn
kernel proteins or decreasing the amount of prolamins would

result in an improvement in the ability of corn to support

22

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25

the growth of nonruminant animals. The observations of Frey
(1951) are in harmony with this well-established fact in
that high protein corn contains a greater proportion of
zein in its total protein than low protein corn.

Corn prolamins, zeins, constitute a family of the
alcohol-soluble corn endosperm storage proteins that are
located within protein bodies (Lending and Larkins, 1989).
They are the major type of protein in the corn kernel,
accounting for 50-60% of the total seed protein (Wilson,
1983) and are almost exclusively located in seeds of the
botanical family Gramineae. Their only known physiologic
role in the plant is as a source of nourishment for the
developing’ embryo. Zeins have unusual amino acid
compositions: Their high glutamine, proline, and
hydrophobic amino acid contents give them.unique solubility
(insoluble in water or aqueous salt solutions, but soluble
in aqueous alcohol), and their deficiency in the animal
essential amino acids, lysine, and tryptophan causes
traditional corn varieties to be poor in protein quality.
Salamini and Baldi (1969) observed a correlation
coefficient of —0.81 when total corn lysine, in several
varieties of corn, was related to the amount of the
alcohol-soluble fraction (zein) in their meals. Tsai et al.
(1983) concluded on basis of similar experiments that:

1. Lysine content as percent of protein decreases when zein

26

as percent of protein increases; 2. Zein as percent of dry
weight increases as the total protein content increases;
3. Lysine as percent of protein is inversely proportional
to the ratio of zein to total protein; and lysine as
percent of dry weight is proportional to the content of
nonzein protein.

Distribution of zein in imature corn was investigated
by Zeleny (1935). He found that zein was nearly absent in
very immature corn but was synthesized rapidly as the corn
approached maturity. The rapid increase in the ratio of
zein to total nitrogen was almost exactly paralleled by the
decrease in water-soluble nonprotein nitrogen.

The nonprolamin proteins traditionally have been
divided into albumins, globulins, and glutelins. Albumins
are defined as water-soluble proteins (Osborne, 1924), but
in too many cases the actual practice has been to define
them as water-extractable proteins. Osborne's original
procedure (1924) separates albumins from globulins on the
basis that, after an extraction with a salt solution, the
albumins remain soluble after dialysis against water,
whereas the globulins are precipitated. The lysine levels
are substantial, thus, the albumins are a good dietary
source of essential amino acids. The globulin proteins are
potential storage proteins and have also a high lysine

content (4.4-5.0%). The glutelin fraction in corn

27

represents a significant proportion of the total protein,

as stated by Dimler (1966), as much as 40 or 50%.

3.0 MATERIALS AND METHODS

3.1 Design

Forty-two corn samples (grab sampled) from different
locations within the State of Michigan and four test weight
corns of 54, 62, 66 and 76 kg/hl (dry matter of all four
test weight corns was 87%) were analyzed for lysine and
minerals. The latter *were also analyzed for protein
fractions and tested in the balance experiment. All corns
were from a Michigan State University Extension survey.
Test weights measurements were done by one person. There
'were :no agronomic details (soil type, fertilization. or
variety of corn). In this study, a metabolic trial
(Schneider and Flatt, 1975) concerning nitrogen retention
and energy utilization in swine was performed with four
test weight corns which came from St. Joseph County. Four
test weights corns were ground and mdxed to obtain
sufficient amounts of each corn for the complete balance
trial. Twelve weaned, crossbreed Yorkshire x Hampshire pigs
averaging 9.3 kg were randomly divided into four groups and
placed individually in metabolism.cages, resulting in three
pigs per treatment. All cages had wire mesh floors suitable

for separated urine and feces collection. The balance trial

28

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31

was divided into four periods of five days each. Pigs were
allowed two days between each period of the balance trial
to adjust to the succeeding diet. Pigs were fed twice
daily, and water was given with the meal at a two to one
ratio. The balance trial was conducted as outlined in Table
4 and the diets fed are given in Table 5. Pigs were fed
only corn during periods III and IV. The results obtained
reflect solely the nutrients available in the corns. Period
IV was a replicate of period III, thus, there are 6
independent sets of observations per corn for statistical
assessment purposes.Final average weight of pigs was 23 kg.
The purpose of the trial was to determine the nitrogen and

energy balances in respect to each test weight corn.

3.2 Collection of Samples

Urine collections were made on a 5-day fixed time
basis. Urine output was recorded and subsamples of 50 ml
were taken, securely sealed and stored until analyses were
performed. Fecal collections were also made on a 5-day
fixed time basis, allowed to dry at ambient temperature,
weighted and later redried for DM determinations. The dried
feces were ground twice through a 2 mm diameter screen in a

Wiley Mill .

32

3.3 Determination of Percent Protein and Nitrogen

All urine and fecal samples were tested for nitrogen
and protein contents by the standard Auto-Kjeldahl method
using the Technicon Auto-Kjeldahl Analyser. Percent of
nitrogen was converted to percent of crude protein by the

coefficient of 6.25 (AOAC, 1992).

3.4 Determination of Gross Energy

Corn, urinary and fecal energies were determined by
the Paar Adiabatic Oxygen Bomb Calorimetric method

(AOAC, 19.92) .

3.5 Determination of Lysine Composition

All of the forty-six corn samples were analyzed for
lysine conposition. The corns were dried and approximately
100 mg were hydrolyzed in 20 ml of 6N hydrochloric acid
under a N atmosphere at 121 °C in an autoclave for 24
hours. The hydrolyzates were filtered and the volume
adjusted to 40 ml. Twenty [11 of hydrolysates were prepared

and derivatized with phenylisothiocyanate (PITC) . The PITC

33

derivatives were diluted to 200 Ill (Waters Manual, 1986)
and 15 Ill were injected onto a 15 cm Pico Tag AA column
(Waters) and eluted with a binary gradient (Waters Manual,
1986). Column temperature was set a 38 °C, flow rate was 1
ml/min., detector UV at 254 nm. Chromotopography was
accomplished on a Waters HPLC system with a 712 WISP
Injector, 2,510 Pumps, 720 Controller, 730 Data Module and

440 Spectrometer.

3.6 Determination of Minerals

Minerals analyses were performed only with corn
samples. Analyses included a Spectro-Fluorometric analyses
of Se which had to be carried out separately from Ca, Zn, P
and Fe. Ca, Zn and Fe were quantitated by atomic absorption
spectroscopy after nitric acid-perchloric acid digestion.
Phosphorus was determined in the nitric-perchloric digest

using the Fiske-Subbarow procedure (AOAC, 1992) .

3.7 Determination of Protein Fractions

Only test corn samples were analyzed for protein

fractions. Albumins and globulins were extracted by 0.5M

34

sodium chloride. Prolamins (Zein) were extracted by 70%
ethanol. After extraction, each residue (for' prolamins
determination) was washed with water to remove salt. The
glutelins were present in the residue (Osborne, 1907).
First set of the salt/water extraction residues (Residue A)
were analyzed for N. Second set of the salt/water and
ethanol extraction residues (Residue B) were also analyzed
for N. Calculations were made as follows:

a) Total corn (N) -Residue A(N) - Albumins and Globulins

In Total corn(N)-Residue B(N) - Albumins,Globulins and Zein
C) (b)-(a) - Zein

d) Residue B . Glutelins

3.8 Calculations and Statistical Analyses

Upon obtaining the data from the N balance study and
gross energy determinations of the corn, fecal and urinary
samples, treatment differences in regards to percent
apparent dry matter digestibility, percent apparent protein
(N) digestibility, percent apparent gross energy
digestibility, percent digestible energy, percent
metabolizable energy, percent absorbed N, percent net
protein utilization, percent N retention and percent

biological value were determined by Anova: Single-Factor

35

(SAS, 1989). When a significant treatment difference
existed, Tukey's Studentized Range (HSD) Test for variable
(Tukeyy 1989) was used to determine significant differences
among treatments. Basis for these statistical analyses were
nitrogen and energy balance values calculated for each corn

using routine procedures (Adeola et al., 1986).

4.0 RESULTS AND DISCUSSION

4.1 Lysine, Crude Protein and Test Weight Distribution

Distribution of crude protein and lysine content in
forty-six corns by counties and in relation to test weight
are presented in Tables 6 and 7, respectively. Distribution
of test weight by counties and locations of corns within
the State of Michigan are presented in Figures 3 and 4,
respectively. Samples number 89 and 90 were excluded from
the observation since they were complete feeds. Corn test
weights varied substantially - i.e. 54 kilogram per
hectoliter to 75 kilogram per hectoliter. The crude protein

content of the corn samples averaged 8.72% compared to a

NRC, 1988 value of 8.50%. Wide variations in protein
content were observed with test weight. For the test weight
corns in range 54-61 kg/hl, the average protein content was
8.70% with a range of 7.3-10.2%, in range 62-65 kg/hl, the
average protein content was 8.85% with a range of 8.1-

10.2%, and finally in range 66-75 kg/hl, the average

protein content was 8.65% with a range of 7.6-9.6%. As
shown, similar data appeared to be the norm for all corn
test weight categories. Apparently the variation in protein
content within a given corn test weight category is about
the same as the variation among test weight categories,

suggesting that significant differences do not exist

36

37

Table 6 Distribution of Crude Protein, Lysine and
Test Weight of Corn by Counties

    
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Dry Crude Test
Corn County Matter Protein Lysine Lysine Weight
(#) (%) (%)* (%)** (%)*** (kg/hl)
5 Allegan 85.6 8.8 0.21 2.38 66
6 Allegan 85.3 8.3 0.20 2.41 63 I
7 Allegan 84.7 8.1 0.23 2.84 66
8 Allegan 87.3 8.7 0.23 2.64 67
9 Ogemaw 87.2 9.6 0.24 2.50 66
10 Ogemaw 88.2 9.8 0.23 2.35 57
i 12 Ogemaw 85.8 9.6 0.23 2.40 55
22 Branch 79.4 8.1 0.23 2.84 63
23 Branch 90.1 8.7 0.22 2.53 55
25 Mecosta 85.7 10.2 0.25 2.45 59
26 Mecosta 89.5 8.9 0.22 2.47 64
I 27 Huron 77.3 8.7 0.23 2.64 59
28 Huron 73.7 8.8 0.24 2.73 54
30 St.Joseph 85.7 7.8 0.25 3.21 55 ]
31 St.Joseph 89.8 7.6 0.24 3.16 56
32 Branch 86.6 8.9 0.24 2.70 73 4
33 St.Joseph 88.8 7.3 0.24 3.29 54 J
34 St.Joseph 86.1 8.5 0.24 2.82 58
35 Cass 86.8 8.8 0.24 2.73 71
F36 Cass 89.7 7.5 0.20 2.67 60
| 37 Cass 85.2 8.5 0.22 2.59 66
| 38 Cass 86.1 8.5 0.22 2.59 64
71 Cass 90.1 8.9 0.27 3.03 68

* Crude protein data obtained from Tom Pilbeam

** Of whole sample

*** Of protein

 

38

 

 

  
    

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

 

  

 

  

 

 

Table 6 (cont'd).

n£;' Crude—3‘ Test
Corn County Matter Protein Lysine Lysine Weight
(it) (96) (%)* (%)*** (kg/hl)
72 Branch 77.0 7.6 ‘0.24 H 3.16 69
73 Eaton 86.1 8.6 0.25 2.91 75
74 Ingham. 90.5 8.6 0.26 3.02 63
75 Eaton 87.5 9.1 0.26 2.86 63
76 Gratiot 86.1 8.7 0.25 2.87 61
77 Kalamazoo 86.4 9.3 0.26 2.79 69
78 Kalamazoo 87.0 9.3 0.25 2.69 62
79 Gratiot 88.1 8.6 0.24 2.79 59
80 Otsego 87.8 9.2 0.24 2.61 66 pl
81 Otsego 87.4 10.2 0.26 2.55 64
82 Otsego 90.0 9.8 0.25 2.55 55
83 Cass 87.5 7.8 0.22 2.82 66
84 Cass 88.5 9.0 0.20 2.22 72
85 Cass 86.3 9.2 0.24 2.61 59
86 Cass 89.7 8.5 0.22 2.59 72
87 Cass 91.2 7.9 0.23 2.91 66
88 Lapeer 88.5 8.9 0.23 2.58 67
89 Cass**** 90.0 18.7 1.25 6.68 N/A
90 Cass**** 87.4 14.4 0.63 4.37 N/A
91 Gratiot 87.2 8.6 0.23 0.23 60
92 Eaton 86.6 8.6 0.23 0.23 65
93 Ottawa 88.4 8.8 0.26 0.26 60
98 Gratiot 88.2 8.6 0.24 0.24

* Crude protein data obtained from Tom Pilbeam

 

** Of whole sample
*** Of protein
**** Feeds

 

 

 

 

   

 

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42

(P>.05) . There was no significant effect of test weight on
crude protein (correlation coefficient-0 . 003) . The
distribution of crude protein and test weight and a
regression plot of the original data, predicted values, and
the regression line(y-8.27+0.003x) are shown in Figures 5

and 6, respectively.
The lysine content of the corn samples averaged 0.24%

compared to a NRC, 1988 value of 0.25%. There was
significant effect of crude protein on lysine (correlation
coefficient-0.32). Lysine content changed proportionally
with crude protein content as shown in Figure 7 and in
regression plot of crude protein and lysine
(y-0.166+0.008x) in Figure 8. In other words, lysine levels
increased or decreased as protein levels changed. These
findings are in agreement with the findings of Arnold et
al.(1977), Paez et al.(l969), Davis et al. (1970), and
Keney (1970) who also found a significant correlation
between nitrogen and lysine in corn and stated, therefore,
that lysine content on dry weight basis increases as the
total nitrogen content increases.

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lysine (correlation coefficients-0.09). Lysine content did
not change proportionally with test weight as shown in
Figure 9 and in regression plot of lysine and test weight
(y-0.252-0.0003x) in Figure 10. It was not possible to
compare distribution of lysine according to test weight
from my findings with other authors' findings, since

related data were not available.

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4.2 Energy and Nitrogen Balance Study

The corns were chosen for energy and nitrogen balance
study according to their test weight of 54, 62, 66, and 76

kg/hl. The crude protein contents of test weight corns were

7.42, 8.03, 8.72, and 8.13%, respectively (Figure 11).

Table 8 presents gross energy and nitrogen intake,
fecal and urinary gross energy and nitrogen, digestible and
metabolizable energy, metabolizable and digestible energy
ratio, absorbed and retained nitrogen, net protein
utilization and biological value, dry matter, gross energy
and nitrogen digestibilities.

The DE values of the 54, 62, 66, and 76 test weight

corns were 3.75, 4.02, 3.88, and 4.09 kcal/g, respectively.
While insignificant on corns 62 and 76 (P>.01), other

pairwise comparisons were significant (P<.01). Similar DE

in corns was reported by Adeola et al. (1986). However, DE
of corn 66 was higher (P<.01) than DE of corn 54 but lower

(P<.05) than DB of corn 62. Distribution of digestible
energy (kcal/g) of test weight corns is presented in Figure
12.

The ME, because it accounts for energy losses from the
animal via urine and is thus a more sensitive indicator of
the animal's physiological state, is more accurate than DE
in evaluating the energy available for maintenance and

productive purposes. However, such a situation implies the

50

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Table 8 The Effect of Test Weight on Energy Balance and
Nitrogen Balance in Young Pigs

 

 

 

 

Corn 54 Corn 62 Corn 66 Corn 76
Item (kg/hl) (kg/hl) (kg/hl) (kg/hl) sin“
Energy balance
No. of pigs 6 6 6 6 N/A
Daily feed intake, 9 (as fed) 400 400 400 400 N/A
Daily cs intake, kcal 1,656° 1,772“ 1,700' 1,760‘ 4.13
Daily fecal dry weight, g 51.5” 49.0” 46.9” 38.9“ 0.58
Daily fecal 02, kcal 154.6” 161.8" 145.3” 124.4” 5.42
Daily DE, kcal 1,502” 1,610’ 1,555c 1,636‘ 4.05
Digestible energy, kcal/g 3.75I 4.02" 3.88” 4.09" 0.02
Energy digested, 4 90.7' 90.9' 91.4' 92.9‘ 0.17
Daily urine, 9 390' 395” 367" 403‘ 1.90
Daily urine as, kcal 23.4 24.1 22.0 24.2 2.81
Daily 1m, kcal 1,478” 1,586' 1,533° 1,612" 2.89
Metabolizable energy, kcal/g 3.70c 3.97‘ 3.83' 4.03‘ 0.02
Energy metabolized, % 89.2” 89.5“ 90.2” 91.6“ 0.34
n : DE 98.7 98.7 98.7 98.5 N/A
Nitrogen balance
Daily nitrogen intake, 9 4.75' 5.12“ 5.56” 5.21° N/A
Daily fecal nitrogen, g 1.08” 1.13“c 1.08“ 0.87” 0.02
Daily absorbed nitrogen, g 3.67“ 3.99"I 4.48” 4.34” 0.03
Daily urinary nitrogen, g 1.94° 2.20” 2.18" 1.98° 0.03
Daily retained nitrogen, g 1.73c 1.79° 2.30b 2.36” 0.04
Net protein utilization, % 36.4° 35.1° 41.4“ 45.3” 0.32
Biological value, % 47.1° 44.9dl 51.3be 54.4" 0.34
Apparent digestibility of DM, 4 87.4" 88.0’ 88.5“ 90.5" 0.21
Apparent digestibility of 0s, 9. 90.6' 90.9' 91.5” 92.9” 0.27
Apparent digestibility of N, 4 77.3’ 78.1’ 80.6” 83.3" 0.34

 

.Standard error of the mean

I"""lteans in the same row with different subscripts differ (P<.05)
MCmMeans in the same row with different subscripts differ (P<.01)

 

52

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need to determine ME for each physiological state. DE has
the advantage of ease of determination, which prompted May
and Bell (1971) to suggest that to combine the advantages
of the two (by assuming that ME is a constant proportion of
DE) would be the most satisfactory approach.

The ME values of 54, 62, 66, and 76 test weight corns

were 3.70, 3.97, 3.83, and 4.03, respectively. All pairwise
comparisons were significant (P<.01) except for corns 62

and 76 (P>.01). ME of corn 54 was lower (P<.01) than other
ME of corns, presumably a reflexion of its lower test
weight and the gross energy content. These results are in
close agreement with Morgan et al.(l975) and Lin et
al.(l987). Distribution of metabolizable energy (kcal/g) is
shown in Figure 13.

The amount of energy lost in urine is represented from
14.2-15.6% of dietary DE content (mean: 14.9%). The mean

ME:DE ratio (x 100), therefore, averaged 98.7%, what is
similar to Morgan et al.(l975) findings. ME as a percentage
of DE did not change significantly across corns as the test
weight of corn increased.

The average daily nitrogen metabolism of pigs fed the
four test weight corns is given in Table 8. The
distribution of the ingested nitrogen of the test weight

corns is shown in Figure 14. When higher amount of nitrogen

was supplied by corns 66 and 76, a significantly (P<.05)
greater percentage of the ingested nitrogen was retained

from these corns than from corns 54 and 62. The absorbed

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nitrogen values of 54, 62, 66 , and 76 test weight corns
were 3.67, 3.99, 4.48, and 4.34 g, respectively. The
absorbed nitrogen differed in all corns.

Corn 66 had higher (P<.05) absorbed nitrogen value
compared to corns 54, 62, and 76, probably a reflexion of
higher nitrogen intake (Figure 15) . The minimum significant

difference among the treatments was 0.124 (P<.01) .

The retained nitrogen values of the 54, 62, 66, and 76
test weight corns were 1.73, 1.79, 2.30, and 2.36 g,
respectively. While insignificant, the retained nitrogen

values were 24.5% higher in corns 66 and 76 (P<.05) than
in corns 54 and 62 (Figure 16). The minimum significant

difference among the treatments was 0.19 (P<.01) .
Nitrogen retention, expressed as a percentage of

either consumed (net protein utilization) or absorbed
nitrogen (biological value), tended to be highest (P<.05)

for corn 76 and lowest (P<.05) for corn 62 and appeared to
have been influenced by low nitrogen intake and high fecal
and urinary nitrogen output, which adversely affected these
values. Similar biological value and net protein
utilization values were reported by Gupta et al.(l979),
Adeola et al.(l986), and Asche et al.(l986). Distribution
of net protein utilization and biological values of four
test weight corns are shown in Figures 17 and 18,
respec tively .

The digestibility of dry matter, gross energy and

nitrogen were significantly (P<.01) higher for corn 76 than

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64

for corns 54, 62 and 66 with no significant difference for
nitrogen digestibility between corns 54 and 62. On average,

there was an increase of 1.6% in dry matter digestibility,

1.3% in gross energy digestibility and 3.4% in nitrogen
digestibility over a test weight range from 54 kg/hl to 76
kg/hl. Linear increase of all digestibility categories was
probably due to decrease of fecal output. Distribution of
dry matter, gross energy and nitrogen digestibilities are
shown in Figure 19, 20 and 21 respectively. The higher
digestibilities of dry matter, gross energy and nitrogen
are consistent with past studies evaluating corn by
Lawrence (1968), Scarbieri et al.(l977), Adeola et
al.(l986), Asche et al.(l986) and Lin et al.(l987).

4 . 3 Minerals

Distribution of the minerals in corn by counties are
presented in Table 9. As shown, data for major elements (Ca
and P) fall within a fairly narrow range, while for trace
elements (Zn, Fe, Se) greater differences exist between
minimum and maximum values. Similar pattern was observed by
Wolnik et al.(l983). Although the absolute concentrations
of the elements vary from sample to sample, corns do not
display distinct patterns of relative elemental variation
even when grown across the state of Michigan. However, all
analyzed corns samples were, as expected, insufficient when

it comes to supplying swine diets with indispensable

65

Table 9 Distribution of the Minerals by Counties

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ca P Fe Zn

Corn County (%) (’6) (pp!!!) (ppm)
5 Allegan 0.096 0.26 20.17 19.31

6 Allegan 0.012 0.28 21.45 19.04

7 Allegan 0.013 0.25 22.08 19.21

P 8 Allegan 0.015 0.31 21.48 19.06
9 Ogemaw 0.016 0.32 23.04 18.64
10 Ogemaw 0.016 0.28 18.71 17.43
12 Ogemaw 0.022 0.32 34.54 19.85
22 Branch 0.015 0.29 22.31 17.63
23 Branch 0.018 0.31 20.31 19.75
25 Mecosta 0.019 0.32 20.49 23.89
26 Mecosta 0.018 0.27 21.89 18.31

| 27 Huron 0.021 0.31 23.85 18.36
28 Huron 0.021 0.33 24.76 19.39

I 30 St.Joseph 0.018 0.31 18.42 17.64
| 31 St.Joseph 0.021 0.25 17.56 17.11
32 Branch 0.021 0.25 26.96 18.85

I 33 St.Joseph 0.021 0.27 23.22 17.17
34 St.Joseph 0.022 0.28 29.39 18.56
35 Cass 0.023 0.31 29.37 22.46

36 Cass 0.019 0.22 21.93 17.31

37 Cass 0.024 0.22 19.32 18.68

I 38 Cass 0.022 0.26 19.51 18.16
71 Cass 0.021 0.28 19.22 17.81

I 72 Branch 0.022 0.25 17.56 16.71

 

 

 

 

 

 

 

 

 

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Table 9 (cont'd) .
Fe
(PP!!!)
73 Eaton 20.91 19.34
74 Inghmm 0.026 0.33 22.82 20.39 0.081
I 75 Eaton 0.025 0.29 22.59 17.54 0.094
76 Gratiot 0.026 0.31 20.41 17.73 0.122
I 77 Kalamazoo 0.027 0.28 21.91 20.35 0.086
I 78 Kalamazool 0.029 0.26 25.31 21.71 0.082
79 Gratiot 0.031 0.27 23.98 18.07 0.082
I 80 Otsego 0.028 0.29 22.02 19.05 0.109
81 Otsego 0.028 0.28 24.11 18.55 0.082
82 Otsego 0.031 0.36 24.52 21.11 0.085
83 Cass 0.031 0.28 18.81 18.56 0.082
84 Cass 0.031 0.27 22.03 19.41 0.082
85 Cass 0.027 0.31 18.65 18.79 0.058
86 Cass 0.031 0.28 23.14 19.29 0.054 n
87 Cass 0.033 0.27 27.43 17.27 0.031
88 Lapeer 0.031 0.27 20.17 17.73 0.0711
89 Cass* 1.54 1.04 604.71 244.27 0.313
90 Cass* 1.17 0.58 247.55 108.14 0.183
i 91 Gratiot 0.096 0.27 21.76 19.21 0.055
I 92 Eaton 0.096 0.31 18.68 18.27 0.054
I 93 Ottawa 0.096 0.34 21.21 19.56 0.071
98 Gratiot 22.65 25.63
Mean N/A 0.032 22.30 19.04 0.056
NRC** N/A 0.030 0.28 33.00 19.00 0.070
* reeds (excluded from calculation of the mean)

** NRC,

1988

67

minerals. According to the requirements of a 25 kg pig
(NRC, 1988), on average, tested corns can supply only 5.3%
of calcium, 56% of phosphorus, 37.2% of iron, 31.7% of

zinc and 37.3% of selenium. Generally, the mineral
content of corn is lower compared to the mineral content in
small grains. In order to prevent deficiencies in pigs, it
is necessary to include supplemental sources of macro and
micro minerals to diets. Comparisons of average values of

individual minerals with NRC values show, that only iron

(-32.4%) and selenium (-20%) were different from tabular
values. Calcium, phosphorus and zinc values are almost
identical to tabular values. Samples 89 and 90 are actually
mixed, composited feeds; this is reflected by their high

concentration of minerals.

4.4 Protein Fractions

The amounts of protein fractions extracted with
various solvents from the test weight corns along with
procedures leading to results are shown in Table 10.
Literature on nutritional quality of corn is largely
limited to interaction between protein content and amino
acids of corn, nitrogen and energy utilization, and effect
of protein fractions on nutritional quality of corn.
However, literature is lacking data on compositional
changes in protein fractions of corn in comparison to

different test weight. Because of this fact, the author

68

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69

could not compare his results with other putative results
on test weight-protein fraction relationships, but could
only compare his results with protein fractions results
from typical (normal test weight) corns.

Extraction of albumins and globulins was carried out
with 0.5!! NaCl and water and removed 11.0, 23.5, 23.7, and

38.7% of albumins and globulins from test weight corns 54,
62, 66, and 76 kg/hl, respectively. Data for corn 54 are
similar to those found by Osborne and Mendel (1914). Corns
62 and 66 kg/hl are consistent with findings of Hertz
(1957). However, amount of albumins and globulins of 76
kg/hl corn are significantly higher than any literature
report. Partial explanation for this fact is that potential
error was induced in salt/water extraction. Extractions
were carried out in numerous experiments (8 times). Despite
the fact that the fineness of the corn was improved through
the procedures, results were identical to those from the

beginning when corns were grounded through a 1 mm sieve.
Extraction of prolamins was accomplished with 70%
ethanol solution and removed 23.0, 23.5, 19.5, and 18.8%
of prolamines from test weight corns 54, 62, 66, and 76
kg/hl, respectively. Results are far below majority of

other authors' findings, though similarity was observed
with Boundy’s et al.(l967) figures. These authors accounted

for only 76.2% of total corn protein in their extracts.

Most likely the difference (23.8%) was not extracted

bysalt,water or ethanol and was apparently detained in the

70

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72

residue. An analogous situation emerged from my
observations when the apparent high glutelins levels of all
test weight corns prompted me to hypothesize that
prolamines were incompletely extracted from.or precipitated
in the glutelins. The methods I adopted for removal of
protein fractions ‘were apparently' not 'well suited for
separation of prolamins from glutelins and were probably
complicated by the tendency for cereal proteins to
associate, for instance alcohol soluble fraction. binds
strongly to glutelins (Bietz, 1983), consequently making it
resistant to more efficient separation. The constant, low
lysine levels across all corns indicate that prolamin
concentrations had to be higher than my values and also
show that protein fractions were apparently unaffected by
test weight. Figures 22 and 23 show distribution of corn
protein fractions as categories and as percent of corn,

respectively.

5.0 SUMMARY

The results of the four experiments, within the limits
of the experimental conditions employed, have led the
author to make the following conclusions:

1. Wide variations in protein content (7.3-10.2%)
were observed among test weight corns. However, similar
data appeared to be the norm for all corn test weight
categories. Apparently the variation in protein content
‘within a given corn test weight category is about the same
as the variation among test weight categories. There was no
significant effect of test weight on crude protein content.

2. There was significant effect of crude protein on
lysine. Lysine content changed proportionally with crude
protein content. In other words, lysine levels increased or
decreased as protein levels changed.

3. There was no significant effect of test weight on
lysine. Lysine content did not change proportionally with
test weight.

4. Lower test weight reduced the amount of energy
available, presumably a reflection of a somewhat lower
caloric density of low test weight corn. Consequently,
producers should attempt to use lightweight corn in less
critical phases of production such as for gestating sows or

finishing pigs.

73

74

5. Protein. quality"va1ues tended. to increase 'with
higher test weight corns.

6. The digestibility of DM, GE and N were
significantly higher for corn 76 than for corns 54, 62, and
66 kg/hl.

7. Two corns with higher test weight retained more
nitrogen (g/day) than the two corns with lower test weight.

8. Major elements (Ca,P) fall within a fairly narrow
range, while for trace elements (Zn,Fe,Se), greater
differences were found between minimum.and maximum.values.

9. Corns do not display distinct patterns of relative
mineral variations across the State of Michigan.

10. Comparison of average values of individual minerals
with NRC values shows, that only Fe (-32.4%) and Se (-20%)
‘were different, while Ca, P and Zn are almost identical to
NRC values.

11. The higher amounts of albumins and. globulins
obtained in this study were most likely due to errors
induced during salt/water extraction and incomplete residue
recovery. Similarly, the lower values for prolamins than
usual or expected were probably the result of incomplete

extraction from glutelins with our procedures.

6 . 0 BIBLIOGRAPHY

AACC Edition. 1987. Corn: Chemistry and Technology, p.202.

Adeola, 0., Young, L.G., Mc Millan, 3.6. and Moran, E.T.
1986. Comparative protein and energy value of OAC
Wintri Triticale and Corn for pigs. J.Anim.Sci.
63:1854-1861.

Agricultural Outlook. USDA, March 1985, p.29.

Alexander, D.H. and Creech, R.G. 1977. Breeding special
industrial and nutritional types. Pages 363-390 in:
Corn and Corn Improvement. Am. Soc. Agronomy, Madison,
WI.

Allee, G.L. and Baker, D.H. 1970. Limiting nitrogenous
factors in corn protein for adult female swine. J.
Anim. Sci. 30:748.

Anonymous. 1969. United States-Canadian Tables of Feed
Composition. Nat. Acad. Sci., Washington, D.C.

Anonymous. 1982. United States-Canadian Tables of Feed
Composition, 3rd ed. Natl. Academy Press, Washington,
D.C. p.148.

AOAC. 1990. Official Methods of Analysis (15th ed.)
Association of Official Analytical Chemists,
Washington, D.C.

ARC. 1967. The nutrient requirements of farm livestock.
No.3. Pigs. Agr. Res. Council, London.

ARC. 1981. The nutrient requirements of pigs. 2nd ed.
Slough, England: Commonwealth Agricultural Bureau.

Arnold, J.M., Bauman, L.F. and Aycock, H.S. 1977.

Interrelations among protein, lysine, oil, certain
mineral element concentrations, and physical kernel

75

76

characteristics in two maize populations. Crop Sci.
17:421-425.

Asche, G.L., Lewis, A.J., Peo, E.R. and Crenshaw, J.D.
1985. The nutritional value of normal and high lysine
corns for weaning and growing-finishing swine when fed
at four lysine levels. J. Anim. Sci. 60:1412-28.

Asche, G.L., Crenshaw, J.D., Lewis, A.J. and Peo, E.R.
1986. Effect of dry, high moisture and reconstituted
normal and high-lysine corn diets and particle size on
energy and nitrogen metabolism in growing swine. J.
Anim. Sci. 63:131-38.

Asghari, M. and Hanson, R.G. 1984. Climate, management and
N effect on corn leaf N, yield and grain N. Agron. J.
76:911-916.

Asplund, J. M. and Harris, L.E. 1969. Metabolizable energy
values of nutrient requirement for swine. Feedstuffs
41(14):38.

Baird, D.M. 1971. Digestibility and energy value of blight-
damaged corn diets for hogs. Feedstuffs, vol.43,
No.37, p.36.

Baird, D.M. 1974. New metabolizable energy values for
swine . Proceedings of the Georgia Nutrition
Conference, pp.88-94.

Baker, D.H., Becker, D.E., Norton, H.W., Jensen, A.H. and
Harmon, B.G. 1969a. Lysine imbalance of corn protein
in the growing pig. J. Anim. Sci. 28:23.

Baker, D.H., Clausing, W.W., Harmon, B.G., Jensen, A.H. and
Becker, D.E. 1969b. Replacement value of cystine for
methionine for young pig. J. Anim. Sci. 29:581.

Baker, D.H., Katz, R.S. and Easter, R.A. 1975. Lysine
requirement of growing pigs at two levels of dietary
protein. J. Anim. Sci. 40:851.

77

Ball, R.O., Atkinson, J.L. and Bayley, H.S. 1986. Proline
as an essential amino acid for young pig. British J.
Nutr. 55:659.

Bayley, H.S., Holmes, J.H.G. and Stevenson, H.R. 1974.
Digestion in the pig of the energy and nitrogen in
dried, ensiled and organic acid preserved corn, with
observations on the starch content of digesta samples.
Canadian J. Anim. Sci. 54:419-27.

Becker, D.E., Jensen, A.N., Terrill, S.W. and Norton, H.W.
1955. The methionine-cystine need of the young pig.
J.Anim. Sci. 14:1086.

Beeson, W.M., Mertz, E.T. and Jackson, H.D. 1951. Effect of
arginine, leucine, phenylalanine and valine on the
growth of weanling pigs.J. Anim. Sci. 10:1037 (Abstr.) .

Bethke, R.M. 1929. The calcium-phosphorus relationship in
the nutrition of the growing chick.Poultry Sci. 8:257.

Bietz, J.A. 1983. High performance liquid chromatography:
How proteins look in cereals. The role of HPLC in
cereal chemistry, AACC 68th Annual Meeting, Kansas
City, MO. Oct.30-Nov.1. 1983.

Bird, H.R. and Olson, D.W. 1972. Effect of fertilizer on
the protein and amino acid content of yellow corn and
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