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This is to certify that the

thesis entitled

THE IMPACT OF SUPPLEMENT WITHDRAWAL AND WHEAT
MIDDLING INCLUSION 0N PORK NUTRIENT QUALITY
AND BONE QUALITY

presented by

DANIEL TOWNER SHAW

has been accepted towards fulfillment
of the requirements for

M. S . degree in Animal Science

 

 

 

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Major professor

Date April 15, 2001

 

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DATE DUE DATE DUE DATE DUE

 

 

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6/01 cJCIRC/DateDuepGS-p. 15

 

THE IMPACT OF SUPPLEMENT WITHDRAWAL AND WHEAT MIDDLING
INCLUSION ON PORK NUTRIENT CONTENT AND BONE QUALITY

By

Daniel Towner Shaw

A THESIS
Submitted to
Michigan State University
in partial fillfillment of the requirements
for the degree of
MASTER OF SCIENCE
Department of Animal Science

2001

ABSTRACT

THE IMPACT OF SUPPLEMENT WITHDRAWAL AND WHEAT MIDDLING
INCLUSION ON PORK NUTRIENT CONTENT AND BONE QUALITY

By
Daniel Towner Shaw

A study was conducted to determine if supplement withdrawal (omission of
dietary vitamin and trace mineral premixes and 2/3 reduction of inorganic P) 28-d pre-
slaughter and wheat middling inclusion affect the vitamin and mineral concentrations of
the longissimus dorsi muscle (LDM), bone quality, and the incidence of bone fi’actures
occurring at slaughter. Supplement withdrawal did not affect LDM thiamin, vitamin E,
Ca, P, Zn, Fe, or Cu concentrations; however, riboflavin and niacin concentrations were
decreased (P < 0.01). Supplement withdrawal increased serum osteocalcin and
pyridinoline concentrations (P < 0.05), indicating an increase in bone turnover;
consequently, bone mineral density, peak force, ultimate shear strength, and percent ash
(P < 0.01) of the metacarpal bone was decreased. Dietary wheat middlings inclusion
increased LDM thiamin, niacin, riboflavin, and vitamin E concentrations (P < 0.04), but
did not alter bone quality. Neither supplement withdrawal nor wheat middlings aflected
the incidence of bone fi'actures at slaughter. The results of this study indicate that
supplement withdrawal and dietary wheat middlings alter the nutrient content of pork.

Additionally, supplement withdrawal increases bone metabolism and decreases bone

quality.

TABLE OF CONTENTS

LIST OF TABLES .............................................
LIST OF FIGURES .............................................
INTRODUCTION .............................................

CHAPTER 1

LITERATURE REVIEW

HISTORY OF SUPPLEMENT WITHDRAWAL .....................
Introduction .............................................
Grth studies .......................................
Bone quality .............................................
Dietary influence on pork nutrient content .....................
Supplement withdrawal and pork nutrient content ...............
Literature cited .......................................

CHAPTER 2

LITERATURE REVIEW

WHEAT MIDLLFEEDS IN SWINE DIETS ...........................
Introduction .............................................
Wheat milling .......................................
Feeding value of wheat middlings ...........................
Wheat middlings in swine diets ...........................
Conclusion .............................................

CHAPTER 3

EFFECT OF SUPPLEMENT WITHDRAWAL AND WHEAT

MIDDLING INCLUSION ON THE NUTRIENT CONTENT OF

PORK, PORK OXIDATIVE STATUS, AND NUTRIENT

EXCRETION ...................................................
Abstract .............................................
Introduction .............................................
Materials and Methods .................................
Results and Discussion .................................
Implications .............................................
Literature cited .......................................

CHAPTER 4

EFFECT OF SUPPLEMENT WITHDRAWAL AND WHEAT

MIDDLING INCLUSION ON BONE METABOLISM, BONE

STRENGTH, AND INCIDENCE OF BONE FRACTURES AT
SLAUGHTER .............................................

NOVI-hb-DUJUJ

v—au—A

Abstract ...... ‘. . .
Introduction .........

Materials and Methods
Results and Discussion

Implications .........
Literature cited . . . .

APPENDIX A .........

OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

iv

6 1
62
63
66
72
73

77

LIST OF TABLES
Table 1. Effect of dietary thiamin supplementation on longissimus
dorsi concentrations, fresh weight basis .................

Table 2. Effect of dietary riboflavin and niacin supplementation on
longissimus dorsi concentrations, fi'esh weight basis ...........

Table 3. Effect of dietary a-tocopheryl supplementation on longissimus
dorsi a-tocopheryl concentrations, fi'esh weight basis .....

Table 4. Nutrient composition of common energy feeds ...........
Table 5. Percentage composition of nursery diets, as fed basis .....
Table 6. Percentage composition of growing and early finishing diets,

as fed basis .........................................
Table 7. Percentage composition of late finishing diets, as fed basis .....
Table 8. Analyzed mineral composition of diets, as fed basis ...........
Table 9. Effects of supplement withdrawal and wheat middling

inclusion rate on pork vitamin and mineral concentrations

and oxidative stability .............................

Table 10. Effects of supplement withdrawal and wheat middling
inclusion rate on growth performance .................

Table 11. Effects of supplement withdrawal and wheat middling
inclusion rate on carcass characteristics .................

Table 12. Efl‘ects of supplement withdrawal and wheat middling
inclusion rate on nutrient excretion during the finishing
phase ...............................................

Table 13. Effects of supplement withdrawal and wheat middling
inclusion rate on serum bone markers .................

Table 14. Effects of supplement withdrawal and wheat middling
inclusion rate on metacarpal bone quality .................

Table 15. Effect of dietary treatment on carcass blood splash ...........

Figure 1.

Figure 2.

LIST OF FIGURES

Diagram of wheat kernel

Flow diagram of milling process .....................

INTRODUCTION

Economic returns in the pork industry are the value of the pork products minus
the costs expended to produce them. Production costs per unit of pork are generally
lowest in pigs that are provided the amounts and types of nutrients that allow each
biological process to proceed at the maximum rate. Deficient or excessive nutrient
intakes relative to biological needs result in lower biological and economical eficiency
of pork production. Furthermore, additions of dietary nutrients that only slightly enhance
performance may not return the cost of the added nutrients.

An area where feed cost per unit of pork may be reduced is the late finishing
period. Feed costs represent 60 to 70% of the total cost of production, and pigs consume
approximately one-third of their total feed intake during the final four weeks of the
finishing period (NRC, 1998). Therefore, even modest decreases in late-finishing feed
costs that cause little or no hindrance to grth will likely decrease production cost per
unit of pork.

The research described in this thesis evaluated the merits of the two methods of
reducing ration costs: supplement withdrawal (removing dietary vitamin and trace
mineral premixes and reducing inorganic P) 28 d prior to slaughter and wheat middling
inclusion. The research provides a comprehensive review of these practices of interest to
producers (growth performance, nutrient excretion), packers (carcass traits, bone
fiactures, blood splash), and consumers (nutrient content of pork).

Thesis Organization
The following thesis is organized as a literature review followed by two papers,

which are in the style and format of the Journal of Animal Science, and will be submitted

to the Journal of Animal Science. The literature review is divided into two sections: the
history of supplement withdrawal in the swine industry and the biological feeding value
of wheat middlings for growing and finishing pigs. The research reported in the papers
was conducted by Daniel T. Shaw under the direction of Dale W. Rozeboom, Gretchen
M. Hill, Diana S. Rosenstein, Alden M. Booren, Michael W. Orth, and Jane E. Link.
Included in the appendix is an explanation of blood splash as it relates to supplement

withdrawal.

CHAPTER 1. HISTORY OF SUPPLEMENT WITHDRAWAL

Introduction

Nutrient concentrations in pig diets are typically based on minimum standards set
by the National Research Council (1998), with sometimes generous safety margins to
ensure against deficiencies. The suggested nutrient requirements for finishing pigs (NRC,
1998) were extrapolated from research trials where pigs were slaughtered at lighter
weights than is common today. As pigs increase in age and size, their nutrient
requirements as a percentage of the diet decrease. Therefore, dietary excesses of many
nutrients are probably common in late-finishing diets.

Growth Studies

Omission of costly ingredients in late finishing diets has been studied for many
years as a means of decreasing feed costs. Gall and associates (1982) replaced the
complete finishing diet with ground corn three weeks prior to slaughter. This practice,
while reducing the cost of the ration, also reduced ADG by 47% and gain/feed by 51%.
Days to market increased by 19 d. An financial analysis identified that the costs
associated with extended days to market and increased kg of total feed required to reach
market weight exceeded the savings of the reduced ration cost, making this practice a
nonviable economic alternative.

Subsequently, researchers in Brazil compared the effects of replacing a complete
finishing ration with a com-soybean meal mixture that provided adequate crude protein.
Pigs fed the diet devoid of all supplemental vitamins and minerals for 21 days tended to
experience a 6.5% reduction in ADG and an 8.6% reduction in ADFI relative pigs fed a

complete and balanced ration. Replacing the complete ration with the com-soybean meal

mixture for either 51 or 71 days prior to slaughter significantly reduced ADG and ADFI
(Donzele et al., 1982).

The more modest approach of removing only vitamin and mineral premixes
and/or reducing inorganic P additions may be a more viable alternative for reducing late-
finishing ration costs. During recent years, several studies have established that removal
of vitamin and mineral premixes from finishing diets 3 to 5 wk prior to slaughter does not
affect growth performance as measured by ADG, ADFI, and gain/feed, or carcass quality
as measured by backfat thickness, loin eye area, marbling, color, firmness, and tenderness
(Patience and Gillis, 1995, 1996; Kim et al., 1997; Mavromichalis et al., 1999; McGlone,
2000).

Bone Quality
The dietary Ca and P concentrations needed to maximize growth performance in
growing-finishing pigs are well defined (NRC, 1998). Maximum bone mineralization and
bone strength requires higher dietary Ca and P concentrations than is required to
maximize growth (Crenshaw et al., 1981; Maxson and Mahan, 1983; Combs et al., 1991).
What remains unknown is whether the increased mineralization resulting fiom higher
mineral supplementation reduces the likelihood of bone fiactures.

In recent years, interest in minimizing inorganic P additions in finishing pigs diets
to reduce nutrient excretion and feed costs has risen. Previous research has indicated that
minimal dietary inorganic P additions are necessary during late finishing to maintain
grth performance. Inorganic phosphorus can be deleted from barley-pea-based diets 75
days prior to slaughter without affecting growth performance if a Ca to total P ratio of

1.3:] is maintained (Michal and Froseth, 1999). Furthermore, the authors observed a 40%

decrease in fecal P concentrations during the withdrawal period. O’Quinn and associates
(1997) reported that removing inorganic P additions 48 d prior to slaughter from
sorghum-soybean meal-based diets reduced fecal P excretion by 12% during the same
period without affecting structural soundness, carcass leanness, and carcass
clmracteristics.

During the withdrawal period, animals draw upon mineral body reserves found in
bone and other tissues to support metabolic requirements that are not met by the diet.
Consequently, bone strength is decreased (O’Quinn et al., 1997); however, it remains
unknown if reducing dietary mineral additions prior to slaughter alters bone metabolism
and decreases bone strength to the extent of increasing the incidence of bone fiactures
occurring at slaughter.

Dietary Influence on Pork Nutrient Content

The publishing date of the available research that evaluates the vitamin and
mineral content of pork reflects the perceived value of the nutrient. Prior to World War
II, meat, poultry, and fish were the primary sources ofthiarnin and niacin in the American
food supply, and dairy products were the primary source of riboflavin. In the mid 1940’s,
flour was emiched with vitamins to ensure against deficiencies in the American
population, making grains the leading dietary source of B-vitamins. Subsequently, the
amount of research investigating the B-vitamin content of pork declined. Increasing the
vitamin E content of pork is a current focus of research as it known to increase the shelf
life and color stability of raw pork.

Because pigs lack a rumen and are unable to synthesize B-vitamins, they require

that most nutrients be provided in the diet. Thus, there is a general relationship between

the vitamin concentrations of the diet and the muscle tissue (Tables 1 and 2). Miller and
coworkers (1943) fed pigs diets containing 2.9, 7.6, and 12.7 mg/kg of thiamin.
Increasing thiamin intake from 2.9 to 7.6 mg/kg and fiom 7.6 to 12.7 mg/kg increased
loin thiamin concentrations by 110% and 15%, respectively. Ensrninger and associates
(1947) reported that the average loin thiamin concentration of gilts fed a thiamin-
deficient diet was 0.09 mg/ 100g, while the average of gilts fed 23 mg/d of supplemental
thiamin was 7.8 mg/ 100g.

Ittner and Hughes (1941) found that increasing dietary riboflavin supplementation
fi'om 0 to 6 mg/d increased loin riboflavin concentrations from 0.14 to 0.25 mg/ 100g.
However, increasing supplementation to 12 mg/d did not further increase loin thiamin.
Miller and coworkers (1943) observed no differences in loin riboflavin concentrations
when feeding diets containing 3.68 to 5.44 mg/kg.

Christensen and associates (1943) showed that longissimus dorsi thiamin
concentrations reflect the level of dietary niacin supplementation. In summary, this
literature review shows that dietary B-vitarnin supplementation influences the
concentrations of thiamin, riboflavin, and niacin present in pork, though muscle
riboflavin appears to reach saturation at moderate levels of supplementation.

Vitamin E acts as an antioxidant at the cellular level to prevent the peroxidation of
polyunsaturated fatty acids. Feeding supranutritive amounts (100 to 700 mg/kg) of
dietary a-tocopherol increases the muscle a-tocopherol concentrations (Table 3),
decreasing lipid oxidation of raw pork (Monahan et al., 1990ab, 1992ab; Asghar et al.,
1991ab; Cheah et al., 1995; Cannon et al., 1996; Jensen et al., 1997; O’Sullivan et al.,

1997; Zamrdi et al., 1998, 1999; Corino et al., 1999; Lauridsen et al., 2000).

 

 

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The trace mineral content of pork is relatively consistent regardless of dietary
levels (Leonhardt and Wenk, 1997). Muscle Zn concentrations are maintained during
times of deficiency (Bentley and Grubb, 1991; O’Leary et al., 1979) Muscle Cu
concentrations are not affected by dietary deficiencies (Ledoux et al., 1989) or excesses
(Zanardi et al., 1998; Lauridsen et al., 2000). An exception to the lack of variation of the
mineral content of meat may be Fe. Injecting growing pigs with 1600 mg of Fe IM fi‘om
Fe-dextran during the nursery and growing phases increased ham Fe concentrations by
21% (Henry et al., 1961), and increasing dietary Fe fi'om 62 to 209 mg/kg for 13 weeks
increased loin Fe concentrations by 38% (Miller et al., 1994).

Supplement Withdrawal and Pork Nutrient Content

The impact of supplement withdrawal on pork nutrient content is not conclusive.
Patience and Gillis (1996) removed vitamin supplements in wheat-barley-canola meal-
based diets 35 (1 prior to slaughter. This resulted in a 20% decrease in longissimus dorsi
(LDM) thiamin concentration, but did not affect the riboflavin, niacin, or pantothenic
acid content. Rozeboom (personal communication), feeding a com-soybean meal-based
diet, removed vitamin and trace mineral supplements 31 d prior to slaughter and also
observed no change in LDM thiamin content. However, supplement withdrawal reduced
LDM iron concentrations by 12% and Zn concentrations by 17%.

Edmonds and Arentson (2001) fed diets devoid of supplemental vitamins and
trace minerals for 6 to 12 wk prior to slaughter. Length of withdrawal did not afi‘ect
grth performance or carcass traits, but reduced vitamin E concentrations of the LDM

and ham muscles by 76 and 55%, respectively. Copper concentrations were reduced by

10

35% in the ham muscle, but not in the LDM. Muscle Zn and Fe concentrations were not
afl‘ected by dietary treatment.

The purpose of this research was to identify the effects of supplement withdrawal
of corn-soybean meal-based diets on pork nutrient content, pork oxidation, nutrient
excretion, bone metabolism and quality, and skeletal integrity at slaughter. The results
provide a comprehensive view of the practice from the perspective of the producer, the

packer, and the consumer.

11

Literature Cited

Asghar, A, J. 1. Gray, A. M. Booren, E. A. Gomaa, M. M. Abouzied, and E. R. Miller.
1991a. Effects of supranutritional dietary vitamin E levels on subcellular deposition of a-
tocopherol in the muscle and on pork quality. J. Sci. Food Agric. 57:31-41.

Asghar, A., J. 1. Gray, E. R. Miller, P. K Ku, and A. M. Booren. 1991b. Influence of
supranutritional vitamin E supplementation in the feed on swine growth performance and
deposition in different tissues. J. Sci. Food Agric. 57:19-29.

Bentley, P. J ., and B. R. Grubb. 1991. Effects of a zinc-deficient diet on tissue zinc
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Cannon, J. E., J. B. Morgan, G. R. Schmidt, J. D. Tatum, J. N. Sofos, G. C. Smith, R. J.
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Combs, N. R, E. T. Komegay, M. D. Lindemann, D. R. Notter, J. H. Wilson, and J. P.
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12

Gall, T. J., M. G. Hogberg, and M. J. Parsons. 1982. Corn vs. finisher diet for the final
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Kim, I. H., J. D. Hancock, J. H. Lee, J. S. Park, D. H. Kropf, C. S. Kim, J. O. Kang, and
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Lauridsen, C., S. K. Jensen, L. H. Skibsted, and G. Bertelsen. 2000. Influence of
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13

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weight, cellularity and zinc concentration of different skeletal muscles in the post-
weanling rat. Br. J. Nutr. 42:487-495.

O’Quimi, P. R, D. A. Knabe, and E. J. Gregg. 1997. Digestible phosphorus needs of
terminal-cross growing-finishing pigs. J. Anim Sci. 75:1308-1318.

O’Sullivan, M. G., J. P. Kerry, D. J. Buckley, P. B. Lynch, and P. A. Morrissey. 1997.
The distribution of dietary vitamin E in the muscles of the porcine carcass. Meat Sci.
45:297-305.

Patience, J. F., and D. Gillis.1995. Removal of vitamins and trace minerals fi'om

finishing diets. Annu. Res. Rep., Prairie Swine Center, Inc., Saskatchewan, Canada. pp
29-31.

14

Patience, J. F ., and D. Gillis. 1996. Impact of pre-slaughter withdrawal of vitamin
supplements. Ann. Res. Rep., Prairie Swine Center, Inc., Saskatchewan, Canada. pp 29-
32.

Pence, J. W., R C. Miller, R A. Dutcher, and P. T. Ziegler. 1945. The rapidity of the
storage of thiamin and its retention in pork muscle. J. Anim. Sci. 4:141-145.

Shaw, D. S., D. W. Rozeboom, G. M. Hill, A. M. Booren, and J. E. Link. 2001. Effects of
supplement withdrawal and wheat middling inclusion on the nutrient content of pork,
pork oxidative stability, and nutrient excretion. Companion paper. Chapter 3.

USDA. 2001. United States Department of Agriculture home page. Available at:
http://www.nal.usdagov/firic/cgi-bin/list_nut.pl. Accessed April 18, 2001.

Zanardi E., E. Novelli, N. Nanni, G. P. Ghiretti, G. Delbono, G. Campanini, G. Dazzi, G.
Madarena, and R Chizzolini. 1998. Oxidative stability and dietary treatment with
vitamin E, oleic acid, and copper of flesh and cooked pork chops. Meat Sci. 49:309-320.

Zanardi E., E. Novelli, G. P. Ghiretti, V. Dorigoni, and R Chizzolini. 1999. Colour
stability and vitamin E content of flesh and processed pork. Food Chem. 67:163-171.

15

CHAPTER 2. WHEAT MILLFEEDS IN SWINE DIETS

Introduction
Corn, without question, is the most common grain used in swine diets in the
United States. However, other energy sources such as sorghum, barley, rye, tricticale,
wheat, and by-product feeds are ofien cost effective substitutes for corn. In much of the
Midwest, wheat middlings, a by-product of flour milling, is a favorite choice due to its

availability and nutrient profile.

Wheat Milling

The milling of wheat flour for human use yields several by-products available for
livestock feeding. A diagram of the wheat seed is shown in Figure 1. The endosperrn,
which is mainly starch, is covered by several fibrous layers that contain high protein and
mineral concentrations. The ultimate purpose of wheat milling is to procure a maximum
amount of flour from the endosperrn with minimum foreign material; the normal flour
extraction rate is 75 to 80 percent (Kent and Evers, 1994). Thus by-products, or
millfeeds, represent 20 to 25 kilograms of every 100 kilograms of wheat processed. A
flow diagram illustrating the milling process appears in Figure 2.

The first step of milling wheat is to remove contaminants from the wheat sample.
The removal of wood, metal, straw, foreign seeds, dust and insect infested wheat kernels
is accomplished by the use of differential sieving, magnetic separation, and aspiration
(Posner and Hibbs, 1997). The removed products are referred to as “screenings” and are

often ground and later mixed with the millfeed.

16

Figure 1. Diagram of Wheat Kernel

(Crop and Food Research Institute, 2001)

 

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Seed Cod (Team—ll. _.

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17

Figure 2. Flow diagram of milling process

WHEAT

l

 

 

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l

CONDITIONING

l

CLEANED AND CONDITIONED GRAIN

l

BREAK

l

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18

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The second step is tempering the kernels to facilitate optimal extraction. Water is
added to the wheat, which was previously stored at low moisture content for maximum
preservation, to raise the moisture content to between 14 and 17% (Posner and Hibbs,
1997). Wheat is stored at this elevated moisture content for 12 to 18 hr. Tempering
toughens the bran and mellows the endosperm; thus when milled, the bran tends to
remain in large particles from which the endosperm can be more efficiently separated.
After tempering the wheat is dried to the desired milling moisture content.

The final phase is the actual milling. The wheat passes through a series of four or
five break rolls, which consist of pairs of spirally fluted iron rollers that rotate in opposite
directions (Posner and Hibbs, 1997). One of the rollers in each pair rotates faster than the
other so a speed difl‘erential exists. As wheat progresses fiom the first break roll through
last, the fluting becomes less coarse, the speed differential decreases, and the opening
between the rollers diminishes. The ground material leaving the break rolls is sieved into
three general streams based on particle size. The finest stream is pure flour. The very
course stream consists of large bran particles. The intermediate stream, also known as
break middlings, consists of shattered bran mixed with endosperm. Break middlings may
either be marketed as millfeed or undergo further processing to separate additional flour.

Further processing of break middlings begins in purifiers that separate
components according to size, shape and specific gravity (Kent and Evers, 1994).
Purifiers consist of a series of screens enclosed in an airtight container. Break middlings
enter at the head of the purifier and are conveyed to the taiL Screen apertures are
graduated from very fine at the head to relatively coarse at the tail. As break middlings

are conveyed across the screen, upward moving air passes through the screen. The less

19

dense material floats upwards with the moving air while the more dense middlings pass
through the screen apertures. The material moved by aspiration, known as tailings,
contains fine particles of fiber and is added to millfeeds. The material that passed through
the coarse screen apertures, known as branny middlings, contains particles of bran and
endosperm that are still stuck together. The branny middlings may either be marketed as
millfeed or enter the scratch system where it passes through very finely fluted break rolls

before reentering at the head of the purifier. The material that passes through the fine

screen apertures of the purifiers is called clean middlings.

'\A
_A

In the reduction system, clean middlings pass through a series of four to six non-
fluted roller mills that further reduce the particle size (Kent and Evers, 1994). In the
dressing stage, the material undergoes final sieving into its flour and millfeed fi'actions.
Wheat germ may also be extracted during the flour dressing sieving.

Millfeeds. All non-flour fractions produced in the milling of wheat are collectively
known as “millfeeds”. Different mill streams may be combined to produce a variety of
products of varying compositions. The following description of wheat milling by-
products supplied to the feed industry comes from the AAFCO (1999) handbook.

(1) Wheat mill run (INF 4-05-206): consists of course wheat bran, fine particles

of wheat bran, wheat shorts, wheat germ, wheat flour, and the offal from the
"tail of the mill”. This product must be obtained in the usual process of
commercial flour milling and must not contain more than 9.5% crude fiber.

(2) Wheat bran (INF 4-05-190): the course outer covering on the wheat kernel as

separated from cleaned and scoured wheat in the usual process of commercial

20

(3) Wheat middlings (INF 4-05-205): consists of fine particles of wheat bran,
wheat shorts, wheat germ, wheat flour, and some of the ofl‘al fiom the "tail of
the mill”. This product must be obtained in the usual process of commercial
milling and must contain not more than 9.5% crude fiber.

(4) Wheat shorts (IFN 4-05-201): consists of fine particles of wheat bran, wheat
germ, wheat flour and ofi°al from the "tail of the mill”. This product must be
obtained in the usual process of commercial milling and must contain not
more than 7% crude fiber.

(5) Wheat red dog (IFN 4-05-203): consists of the ofi‘al from the ”tail of the mill"
together with some fine particles of wheat bran, wheat germ, and wheat flour.
This product must be obtained in the usual practice of commercial milling and

must contain not more than 4% crude fiber.

Feeding Value of Wheat Middlings

Wheat middlings as an energy source. The organic matter of wheat middlings,

like that of cereal grains, is largely carbohydrate. Wheat middlings are primarily

composed of the intermediate layer of the wheat kernel between the endosperm and the

outer bran covering. The cells of this layer, known as the aleurone layer, are the primary

source of DB in wheat middlings. The non-ruminant is able to completely break down the

aleurone layer including the cell walls, although a portion of the carbohydrate and about

10 percent of the protein are not absorbed and appear in the feces (Saunders et al., 1969;

Saunders and Kohler, 1972).

Whole wheat grain contains about 82% of the white-starchy endosperm, which

cannot possibly be separated exactly fiom the 18% of the bran, aleurone, and the embryo.

21

Thus, three to ten percent of the endosperm of whole wheat ends up in wheat middlings.
The endosperm fiaction of wheat middlings contains three percent of readily soluble
monosaccharides, disaccharides, and oligosaccharides (Lineback and Rasper, 1988).
Starch is the most abundant carbohydrate in the endosperm comprising 63 to 72 percent
of the total organic matter (Pomerenz and MacMasters, 1968). The two components of
starch, amylose and amylopectin, are essentially 100% digested in the small intestine of
the non-ruminant (Lin et al., 1987).

Wheat middlings may contain a maximum of 9.5% CF. Fiber digestion, occurring
primarily in the cecum and the large intestine, is a microbial fermentation process.
Volatile fatty acids formed during fiber fermentation serve as a secondary energy source
for pigs and may provide 14 to 16% of the energy requirements of the growing pig
(Imoto and Namioka, 1978; Kass et el., 1980; Lin et al.,1987).

Wheat middlings contain 3,075 kcal/kg of DE and 3,025 kcal/kg of ME (NRC,
1998). While these values are somewhat lower than that of other grains (Table 4), wheat
middlings is generally regarded as a satisfactory energy source in swine rations.

Wheat middlings as a protein source. Although grains are primarily considered as
contributors of energy, the high levels at which they are used means they are incidentally
suppliers of a considerable portion of the dietary protein. Consequently, CP and amino
acid profile becomes an additional point of importance when fed to non-ruminants.
Wheat middlings compares very favorably to other grains in regard to protein quality and
quantity (Table 4).

Wheat middlings as a micro-nutrient source. The most expensive feed ingredients

in swine rations are inorganic phosphorus and vitamin and mineral premixes. Including .

22

 

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23

primary feed ingredients with high rnicronutrient concentrations in the ration formulation
lessens the amount of supplementation necessary for maximum growth performance.
Wheat middlings are an excellent source of P and most vitamins and minerals (Table 4).

Variability. Although wheat middlings are widely used throughout the world and
can supply a considerable proportion of the protein, energy, and trace elements in swine
diets, the variability in nutrient content is a concern. There are five primary classes of
wheat produced in the United States: hard red spring, sofl red winter, hard red winter,
durum, and white; and within each class there are a number of species, each with a
distinct nutrient profile (Oldfield, 1970). When provided with such a variety of inputs,
there is no practical way for millers to produce flour to the buyers' specifications and also
produce standardized millfeeds.

Wheat middlings are classified according to their bulk density as being "heavy" or
"light". Heavy wheat middlings contain a high proportion of starchy endosperm attached
to the bran. Light wheat middlings contain bran that is relatively free of endosperm.
Heavy wheat middlings have a higher feeding value than light middlings for growing-
finishing swine (Cromwell et al., 1992).

Wheat middlings have an average bulk density of 320 g/L, but the variation
ranges fi'om 289 to 365 g/L (Cromwell et al., 2001). Normal CP and P variation of wheat
middlings are 14.6 to 17.8 percent and .70 to 1.19 percent, respectively, with the higher
values associated with light middlings. Selenium content of wheat middlings varies by

the region in which the wheat was raised.

24

 

Wheat Middlings in Swine Diets
Fiber in growing-finishing diets. The use of wheat middlings in growing-finishing
diets is limited by its fiber content. Dietary fiber may dilute DE to the point that feed
intake is restricted by physiological fill. Growing swine offered diets containing 6 to 8%
CF are not able to consume enough feed to meet their energy needs (Hochstetler et al.,

1959; Drewry, 1981). However, when DE does not decrease, incorporation of fibrous

ingredients such as wheat bran, cellulose and ground corn cobs does not affect

. '(Lfi'. 1

performance (Troelson and Bell, 1962). Likewise, when ME levels are held constant, it:
dietary inclusion of cottonseed hulls, wheat bran, and rice mill feeds do not decrease
performance (Baird et al., 1970).

Wheat middlings for growing-finishing pigs. A number of studies compared the
biological value of wheat millfeeds to other cereal grains as a major energy source in
growing-finishing swine rations. Generally these studies follow two patterns: either
equivalent substitution of grains on a unit weight basis or dietary inclusion based on
“least cost” ration formulation adjusted for lysine and/or energy. Experimental results
most likely favor wheat middlings when rations are balanced for both lysine and energy.

Conrad and Harrington (1969) conducted a study in which wheat middlings
replaced corn on a pound for pound basis. Their results showed a decrease in ADG and
feed efliciency when growing and finishing pigs consumed diets containing more than
20% wheat middlings.

Researchers at the University of Guelph studied extensively the use of wheat
shorts in market pig diets. Wheat shorts, like middlings, are comprised primarily of cells

of the aleurone layer of the wheat kernel and contain a maximum of 7% CF. Young

25

(1980) reported two studies in which he evaluated the influence of wheat short inclusion
rate on pig performance. In both trials, wheat shorts obtained fiom the milling of hard red
spring wheat comprised either 0, 32.2, 64.4, or 96.6% of the diet; corn and soybean meal
were allowed to float to maintain CP levels.

In trial 1, 64 pigs weighing 18 kg were fed the experimental diets for 8 weeks.
Analyzed lysine and CP concentrations of all diets exceeded minimum recommended
levels. However, the DE content of the diets containing wheat shorts was lower than
recommended levels. Rate of gain was decreased with dietary levels of wheat shorts
above 64.4%. There was also a linear decrease in gainzfeed as level of wheat shorts
increased.

In trial 2, 64 pigs weighing 21 kg were fed to approximately 90 kg or for 98 days,
whichever came first. Animals were fed in 2 phases, from start to 50 kg and from 50 kg
to slaughter. There was a quadratic decrease in ADG up to 50 kg with increasing levels of
wheat shorts. From 50 kg to slaughter, ADG decreased in a linear manner as level of
wheat shorts increased. Dietary level of shorts did not affect ADFI. The author attributed
differences in performance between the two trials to differences in the wheat short bulk
densities. The wheat shorts used in the second trial contained considerably more ADF
than those used in the first (16.5 vs. 10.4%, respectively). Likewise, the estimated DE
values of the shorts used in the first trial were appreciably greater than those used in the
second (3.38 vs. 3.02 kcal/g, respectively).

Patience and coworkers (1977) at the University of Guelph conducted a grth
trial evaluating the effect of level of wheat short inclusion in typical com-soybean meal

diets. Thirty-one pigs were allotted to receive a 15% CP diet containing either 0, 9.7,

26

19.3, 29.0, 38.6, 48.3, 58.0, 67.6, 77.3, 86.9, or 96.9% wheat shorts. Pigs were marketed
when a carcass weight of about 70 kg was expected. Wheat short inclusion rates above
19.6% tended to depress ADG, though the trend was not significant. However, there was
a linear depression in feed efliciency.

Erickson (1979) fed 96 crossbred pigs growing-finishing diets containing 0, 20,
40, or 60% wheat middlings milled from white winter wheat. Diets were pelleted and
balanced for lysine and available P. Neutral detergent fiber varied from 38 to 41% in the
grower diets and 33 to 37% in the finishing diets. Increasing the level of wheat middlings
did not affect ADG or gain/feed. The author suggested that there may have been no
difference because the ME values of the diets containing wheat middlings were very
similar to the com-soybean meal-based control diet. As level of wheat middlings
inclusion increased, the amount of soybean meal and dicalcium phosphate required
decreased, reducing the overall cost of the ration. The control diets also contained a
binder to improve pellet quality. Removing the non-nutritive pellet binder in diets
containing wheat middlings fi‘eed up 2.5% more nutritive space in the diet. Pellet quality
did not deteriorate, rather pellet quality improved as the percentage of wheat middlings
increased.

Erickson and coworkers (1985) evaluated the effects of increasing levels of wheat
middlings on pig performance. In the first study, control diets were formulated to meet
NRC requirements for starting, growing, and finishing pigs. Wheat middlings replaced
corn on a pound for pound basis at 0, 10, 20 and 30% of the diet. One hundred sixty
crossbred pigs were allotted to the four dietary treatment groups. In the starting phase,

ADG and gain/feed linearly decreased and ADF I linearly increased as concentration of

27

dietary wheat middlings increased. However, pigs receiving 10 to 30% wheat middlings
appeared to experience compensatory gain during grower period as they tended to have
higher ADG than pigs consuming the control diets. Wheat middling inclusion in the
finishing diets and overall did not afiect ADG, but increased feed intake and decreased
feed eficiency.

In the second study, the wheat middling inclusion rates in the growing and

finishing diets were 0, 20, 40 and 60%. All diets were calculated to meet NRC

- in: mumm- it'll“:
I a -

requirements and were balanced for lysine. Feeding 96 crossbred pigs increasing amounts a
of wheat middlings linearly depressed ADG during both the growing and finishing

phases. Wheat middling inclusion did not affect ADF I and linearly decreased feed

efiiciency in the finisher phase, but not in the grower phase. The authors attribute the lack

of agreement in the grower pig performance of these two trials to the dietary lysine

levels. In trial one, wheat middlings replaced corn on an equal weight basis. Thus, as the

level of dietary wheat middlings increased fi'om 0 to 30%, the calculated lysine level

increased fi'om .79 to .92%. In trial two, all diets were formulated to contain .75% lysine.

The higher lysine levels in the diets containing wheat middlings of trial one may have

prevented the decreased grower performance observed in trial two.

O'Heam and Easter (1983) conducted two growth trials to evaluate the effect of
various levels of wheat middlings inclusion on nursery pig performance. The average pig
starting weight in both trials was 8.64 kg, and the estimated DE of the wheat middlings
used in both trials was 2.89 kcal/g. In trial 1, a com-soybean meal-based control diet was
compared to diets containing 30% wheat middlings with and without tallow to determine

ifenergylimitedperformance.Thetrialwas28dinlength. Therewerenodifi‘erencesin

28

ADG or ADFI due to the addition of wheat middlings with or without added tallow.
Energy was not a limiting factor in using wheat middlings in the nursery diets, suggesting
that greater wheat middlings levels may be used.

In trial 2 the researchers utilized increasing levels of wheat middlings (0, 28.9,
56.7, and 85.0%) in com-soybean meal-based diets to determine at which inclusion rate
grth performance was depressed in the nursery pig. Diets were fed for 28 days. As the
level of middlings in the diets increased, ADG and gain/feed decreased. Although diets
were formulated to be isonitrogenous, the diets containing wheat middlings contained a
poorer overall amino acid profile than the control diet, which may have compromised
performance. Protein quality may be a limiting factor in using wheat middlings in
nursery diets.

Cromwell and associates (1992) evaluated the feeding value of two sources of
wheat middlings in pigs weighing 37 to 100 kg. The bulk density of the Source A
middlings was relatively low and the bulk density the Source B middlings was relatively
high. Wheat middlings were added to the diet, on a lysine basis, at levels of 0, 10, 20, 40,
and 60%. Feed intake was not affected by level of middling inclusion. Pigs fed Source A
middlings grew slower and less eficiently as the level of middlings increased in the diet.
For pigs fed Source B middlings, ADG and gain/feed were not affected with up to 20%
inclusion, while grth performance was only slightly reduced with 40% inclusion in the
diet.

Conclusion
Wheat middlings with a heavy bulk density can constitute up to 20% of swine

growing-finishing rations without afi‘ecting performance. Light wheat middlings can

29

comprise 10 to 15% of growing-finishing diets. Wheat middlings can be used in nursery
diets at an inclusion level of 5 to 10%, but care should be taken to maintain an adequate
amino acid profile. Higher levels of wheat middlings may be incorporated into the rations
of pigs with lower metabolic requirements (older, less lean gain potential). Furthermore,
the moderately depressed grth performance tlmt may accompany higher inclusion rates
(greater than 30%) may be economically practical if the price of wheat middlings is

suficiently lower than that of the primary feed ingredients it replaces.

30

Literature Cited

AAFCO. 1999. Oflicial Publication of Association of American Feed Control Oflicials,
Oxford, IN.

Baird, D. M., H. C. McCampbell, and J. R Allison. 1970. Levels of crude fiber with
constant energy levels of growing-finishing swine using computerized rations. J. Anim.
Sci. 31 :518-525.

Conrad, J. H., and R B. Harrington. 1969. A comparison of energy values and the
addition of amino acids in linear programmed growing-finishing diets. Maryland Nutr.
Conf., Washington, DC, p. 36.

Cromwell, G. L., T. R. Cline, J. D. Crenshaw, T. D. Crenshaw, R. A. Easter, R C. Ewan,
C. R Hamilton, G. M. Hill, A. J. Lewis, D. C. Mahan, J. L. Nelssen, J. E. Pettigrew, T. L.
Veum, and J. T. Yen. 2001. Variability among sources and laboratories in nutrient
analysis of wheat middlings. J. Anim Sci 79 (In press).

Cromwell, G. L., T. S. Stahly, and H. J. Monegue. 1992. Wheat middlings in diets for
growing-finishing pigs. J. Anim. Sci. 70 (Suppl. 1):239 (Abstr.).

Crop and Food Institute. 2001. New Zealand Crop and Food Research Institute home
page. Available at: http://www.crop.cri.nz/foodinfo/millbake/whgrain/htm. Accessed
April 14, 2001.

Drewry, K J. 1981. Postwean performance of crossbred pigs fed nomral and high fiber
diets. J. Anim. Sci. 52:197-209.

Erickson, J. P. 1979. Wheat middlings in swine diets. 1. Performance 11. Nitrogen and
phosphorus utilization 111. Economic assay. Research Report 386, Michigan St. Univ. Ag.
Exp. Sta, East Lansing, MI.

Erickson, J. P., E. R Miller, P. K. Ku, G. F. Collins, and J. R Black. 1985. Wheat
middlings as a source of energy, amino acids, phosphorus and pellet binding quality for
swine diets. J. Anim Sci. 60:1012-1020.

Hochstetler, L. N., J. A. Hoefer, A. M. Pearson, and R W. Luecke. 1959. Effect of
varying levels of fiber of different sources upon grth and carcass characteristics of
swine. J. Anim. Sci. 18:1397-1404.

Imoto, S., and S. Namioka. 1978. VFA production in the pig large intestine. J. Anim. Sci.
47:467-478.

Kass, M. L., P. J. Van Soest, and W. G. Pond. 1980. Utilization of dietary fiber fi'om

alfalfa by growing swine. II. Volatile fatty acid concentrations in and disappearance from
the gastrointestinal tract. J. Anim. Sci. 50:192-197.

31

Kent, N. L., and A. D. Evers. 1994. Technology of Cereals. 4th ed. Elsevier Science,
Ltd., Oxford, United Kingdom

Lin, F. D., D. A. Knabe, and T. D. Tanksley, Jr. 1987. Apparent digestibility of amino
acids, grow energy, and starch in corn, sorghum, wheat, barley, oat groats and wheat
middlings for growing pigs. J. Anim. Sci. 64:1655-1663.

Lineback, D. R, and V. F. Rasper. 1988. Wheat Carbohydrates. In: Y. Pomeranz (ed.)
Wheat: Chemistry and Technology. American Association of Cereal Chemists, Inc., Saint
Paul, MN.

NRC. 1998. Nutrient Requirements of Swine. 10th ed. National Academy Press,
Washington, DC.

O'Heam, V. L. and R A. Easter. 1983. Evaluation of wheat middlings for swine diets.
Nutrition Reports International. 28:403-411.

Oldfield, J. E. 1970. A reappraisal of wheat in swine rations. In: Wheat in Livestock and
Poultry Feeds: Proceedings of an International Symposium at Oklahoma State University,
June 18-19, 1970. Stillwater, OK

Patience, J. F., L. G. Young, and I. McMillan. 1977. Utilization of wheat shorts in swine
diets. J. Anim. Sci. 45:1294-1301.

Pomeranz, Y., and M. M. MacMasters. 1968. Structure and composition of the wheat
kernel. Baker’s Digest. 42:24-29, 32.

Posner, E. S., and A. N. Hibbs. 1997. Wheat Flour Milling. American Association of
Cereal Chemists, Inc., St. Paul, MN.

Saunders, R. M., and G. O. Kohler. 1972. In vitro determination of protein digestibility in
wheat millfeeds for monogastric animals. Cereal Chem. 49:98-103.

Saunders, R M., H. G. Walker, Jr., and G. O. Kohler. 1969. Aleurone cells and the
digestibility of wheat mill feeds. J. Poult. Sci. 48: 1497-1 503.

Troelson, J. E., and J. M. Bell. 1962. Ingredient processing interrelationships in swine
feeds. IV. Effects of various levels and kinds of fibrous diluents in finisher rations, fed as
meal or pellets on performance and carcass quality in swine. Can. J. Anim Sci. 42:63-74.

Young, L. G. 1980. Lysine addition and pelleting of diets containing wheat shorts for
growing-finishing pigs. J. Anim. Sci. 51:1113-1121.

32

CHAPTER 3. EFFECT OF SUPPLEMENT WITHDRAWAL AND WHEAT
MIDDLING INCLUSION ON THE NUTRIENT CONTENT OF PORK, PORK
OXIDATIVE STABILITY, AND NUTRIENT EXCRETION.l

A paper to be published in the Journal of Animal Science

D. T. Shaw, D. W. Rozeboom, G. M. Hill, A. M. Booren, and J. E. Link.
Department of Animal Science, Michigan State University, East Lansing, 48824
Abstract
A study was conducted to determine if supplement withdrawal (omission of

vitamin and trace mineral premixes and 2/3 reduction of inorganic phosphorus) for 28 d
pre-slaughter in com-soybean meal-based diets containing either 0 or 30% added wheat
middlings affects the nutrient content and oxidative stability of the longissimus dorsi
muscle, growth performance, carcass characteristics, and nutrient excretion. Crossbred
pigs (11 = 62) were blocked by weight and assigned to one of four treatments in a 2 x 2
factorial design (with or without supplement withdrawal; 0 or 30% wheat middlings).
Supplement withdrawal decreased longissimus dorsi riboflavin, niacin, and P
concentrations (P < 0.05). Longissirnus dorsi thiamin, vitamin E, Fe, Cu, Zn, and Ca
concentrations were not altered. Inclusion of 30% wheat middlings increased longissimus
dorsi thiamin, niacin, riboflavin, and vitamin E concentrations (P < 0.04) and decreased
Cu concentrations (P < 0.04). However, wheat middling inclusion did not affect
longissimus dorsi Ca, P, Fe, and Zn concentrations. Dietary treatment did not affect either
Cu/Zn superoxide dismutase or glutathione peroxidase activity in the loin. In diets

containing firll vitamin and mineral supplementation, wheat middling inclusion decreased

 

1 Appreciation is expressed to Roche Vitamins Inc. for vitamin E analysis

33

fecal Ca, Cu, Fe, and Zn concentrations (P < 0.01) and increased fecal Mn (P < 0.01).
Supplement withdrawal decreased fecal Ca, P, Cu, Fe, Mn, Zn concentrations (P < 0.01).
Supplement withdrawal did not influence ADG, ADF I, gainzfeed, or carcass traits. The
results from this study indicate that supplement withdrawal and dietary wheat middling
inclusion alter pork nutrient content and nutrient excretion, but not the oxidative stability
of pork.

Introduction

Removing dietary vitamin and mineral premixes from finishing diets 3 to 5 wk
prior to slaughter does not afl‘ect pig growth and carcass traits (Patience and Gillis, 1995,
1996; Kim et al., 1997; Mavromichalis et al., 1999; McGlone, 2000). Deleting inorganic
phosphorus fiom barley-pea-based diets 75 (1 prior to slaughter does not affecting growth
performance and decreases fecal P by 40% during the removal period (Michal and
Froseth, 1999). O’Quinn and associates (1997) demonstrated that removing inorganic P
supplements 48 d prior to slaughter fiom sorghum-soybean meal-based diets reduced
fecal P excretion by 12% without affecting structural soundness, carcass leanness, or
carcass quality.

The effect of supplement withdrawal on pork’s nutrient content is not conclusive.
Patience and Gillis (1996) removed dietary vitamin supplements fiom wheat-barley-
canola meal-based diets during the firml 35 (1 prior to slaughter and found that the
longissimus dorsi muscle (LDM) thiamin concentration was reduced by 20%.
Longissirnus riboflavin, niacin, or pantothenic acid concentrations were not affected.
When Rozeboom (personal communication) removed vitamin and trace mineral

supplements 31 d prior to slaughter fiom com-soybean meal-based diets, LDM thiamin

and Mg concentrations were not changed, but Fe and Zn concentrations were reduced by
12 and 17%, respectively.

Edmonds and Arentson (2001) fed diets devoid of supplemental vitamins and
trace minerals for 6 to 12 wk prior to slaughter. Length of withdrawal did not affect
growth performance or carcass traits. However, vitamin E concentrations of the LDM and
ham muscles were reduced by 76 and 55%, respectively. Copper concentrations were
reduced by 35% in the ham muscle, but not in the LDM. Muscle zinc and iron
concentrations were not affected by dietary treatment.

The objective of our research was to determine the effect of withdrawal of
vitamin and trace mineral premixes and 2/3 reduction of inorganic phosphorus 28 d prior
to slaughter on the nutrient content and oxidative stability of pork, growth performance,
carcass characteristics, and nutrient excretion. Furthermore, this research evaluated the
effect of dietary wheat middling inclusion on the same parameters.

Materials and Methods

Animal Use and Care. The experimental protocol used in this study was approved
by the All-University Committee on Animal Use and Care at Michigan State University
(AUF number: 01/00-030-00).

Experimental Design. Crossbred barrows [(Yorkshire x Landrace) x DRU or
(Yorkshire x Musculor)] were blocked by weight and allotted to dietary treatments
arranged in a 2 x 2 factorial design, replicated twice over time. The factors evaluated
were the efi‘ects of supplement withdrawal (omitting vitamin and trace mineral premixes

and 2/3 of the inorganic phosphorus) 28 d pre-slaughter in com-soybean meal-based diets

35

containing either 0 or 30% added wheat middlings. Replication 1 was conducted from
February to June, and replication 2 was conducted fi'om July to November.

Sixty-two pigs with an average initial weight of 8.5 i 0.7 kg were individually
penned (1.51 x 1.58 m) in a totally enclosed, ventilated nursery-to-finish facility, with
23% solid-concrete and 77% slatted-concrete flooring. Pigs were fed 6 dietary phases to
meet the changing physiological needs of the pigs in the nursery through early finishing
periods. These diets met or exceeded NRC (1998) recommendations for all nutrients.
Thirty pigs received typical com-soybean meal-based (CSBM) diets. The remaining 32
pigs received com-soybean meal-based diets with added wheat middlings (CSBM+WM)
at the inclusion rates of 5% in nursery diets, 15% in the transition diet, and 30% in
growing and early finishing diets. Diets were calculated to contain identical lysine, ME,
Ca, and total P concentrations for each phase and had identical vitamin and trace mineral
premixes additions. The compositions of the nursery and transition diets are presented in
Table 5 and the growing and early finishing diets in Table 6.

Three vitamin premixes were utilized in this study, each prepared to provide the
vitamins at or slightly above NRC (1998) recommendations for various stages of growth
The premixes were stored in air-tight containers at -20° C until diets were mixed.
Complete feeds were mixed weekly and were stored at 5° C to maintain vitamin activity.
Any feed that remained in the feeders more than 72 hr was weighed and discarded.

Dietary Treatments. Twenty-eight days prior to slaughter and at an average age of
114 d and weight of 79.0 kg, barrows were provided late finishing diets formulated to
contain identical lysine and ME concentrations. Vitamin and trace mineral premixes and

2/3 of the inorganic P were removed from the diets of 15 pigs receiving CSBM diets and

36

 

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16 pigs receiving CSBM+WM diets. Limestone additions were adjusted to maintain a Ca
to available P ratio of 2.5:1.

Performance and Sample Collection. Pig weights and feed disappearance were
determined for each dietary phase and were used to calculate ADG, ADFI, and gain/feed.
Random samples of feed were placed in whirl-pac bags and fiozen at —20° C until
analyzed for thiamin, riboflavin, niacin, vitamin E, Ca, Cu, Fe, Mn, P, and Zn content.
Ten random samples of wheat middlings were collected for bulk density measurement
and were stored at —20° C until analyzed for Ca, Cu, Fe, Mn, P, and Zn.

To quantify fecal nutrient excretion during the early and late finishing periods, the
top portion three fi‘eshly voided feces were obtained fiom each pig 48 hr prior to
placement on the late finishing diet, and again 48 hr prior to slaughter. Fecal samples
were weighed, freeze-dried, ground in a stainless steel blender, and frozen at -20° C until
mineral analyses were performed.

Upon reaching an average live weight of 103.4 kg, all pigs were slaughtered at the
Michigan State University Meat Laboratory according to standard operating procedures.
Dressing percentages were calculated using hot carcass weights. Following a 24 h chill at
1° C, longissimus muscle area and bacld‘at depth were recorded at the 10th rib. Two 1-in.-
thick loin chops were collected beginning at the tenth rib and proceeding anteriorly. The
LDM was removed and flown at ~80° C until analyzed. Tissue from the initial chop was
analyzed for thiamin by fluorometric method and riboflavin and niacin by microbial
method (AOAC, 1995). The vitamin E content of the second chop was determined as DL-

a-tocopherol by the method of Liu et al. (1996). The remaining tissue from the second

41

chc

310.

C0;

COHCC

chop was analyzed for Cu/Zn superoxide dismutase activity (Cu/ZnSOD), glutathione
peroxidase activity (GPX), and mineral concentrations.

Mineral Analyses. Feed, LDM, and fecal samples obtained in replication 1 were
prepared for mineral analyses using nitric-perchloric acid wet digestion (Hill et al., 1983).

Due to equipment failure, feed, LDM, and fecal samples obtained in replication 2 were

prepared for mineral analyses using microwave digestion (Model HP-500Plus, CEM,

Matthews, NC). For feed and fecal microwave digestion, 10 mL of nitric acid (70%) was 1”
added to either .5 g of feed sample or .4 g of fecal sample in a pressurized Telfon-lined
digestion vessel. For LDM digestion, approximately .5 g of LDM samples was sliced
fi'om within the area of the fiozen tissue and 5 mL of nitric acid and 2 mL of double
distilled water were added. Samples were allowed to digest for 1 hr at room temperature.
Vessels were then placed in the microwave digestor and power was intermittently applied
for 25 min to gradually increase vessel pressure to 210 psi while maximum vessel
temperature was 210° C. Vessels were maintained at 210 psi for 10 min, were allowed to
cool for 10 min, and were vented. Two mL of hydrogen peroxide (30%) was added to the
digested feed and fecal samples and 1 mL was added to the digested LDM. Digested
samples were poured into volumetric flasks and brought to a uniform volume.

Calcium, copper, iron, manganese, and zinc armlyses were conducted by flame
atomic absorption spectrophotometry (Smith-Heifije 4000, Thermo Jarrell Ash
Corporation, Franklin, MA), and P concentrations were determined using the DU 7400
spectrophotometer (Beckman, Palo Alto, CA). Feed, LDM, and fecal mineral

concentrations were reported on an as-fed, flesh, and DM basis, respectively.

42

Instrument accuracy for all mineral analyses was established using bovine liver
standard (1577b; NI ST: National Institute of Standards and Technology, Gaithersburg,
MD). All glassware used in mineral analyses was washed in 30% nitric acid and rinsed
with double deionized distilled water.

Superoxide Dismutase and Glutathione Peroxidase Activities. Longissirnus dorsi
muscle Cu/ZnSOD (EC 1.15.1.1) activity was determined with the method of Hill et al.
(1999). Longissirnus dorsi muscle samples (approximately 1 g) were sliced fiom within
the area of the frozen tissue and homogenized with an Ultra Turrax T25 homogenizer
(Tekmar—Dohrmann Corp., Cincinnati, OH) in 10 x volumes of ice—cold potassium
phosphate buffer (pH 7.2, .05 M phosphate, .24 M sucrose) using a tissumizer probe
(SZSN-IOG, IOImn diameter). The subsequent procedures were the same as for red blood
cell hemolysates in the Hill et al. method. One writ of Cu/ZnSOD activity was defined as
the amount of SOD necessary to inhibit the autoxidation of pyrogannol by 50%. Muscle
GPX (EC 1.11.1.9) activity was determined with the method of Sunde and Hoekstra
(1980). One GPX unit was defined as 1 pmol NADPH oxidized per minute, using the
molar extinction coemcient of 6.22 x 103 for NADPH and the stoichiometry of reaction
of 2 moles GPX formed per mole NADPH oxidized. Protein concentrations of the
supernatant were determined by the method of Lowry et al. (1951), and units of
Cu/ZnSOD and GPX activity were expressed per gram of protein.

During replication 2, two pigs receiving CSBM diets were removed fi'om the
experiment during the growing phase due to health considerations. One pig contracted a
respiratory disease and the other a severe middle ear infection. One of the pigs would

have received a supplement withdrawal diet in the late finishing phase.

43

. . Statistical Analysis. All data were analyzed by least squares AN OVA “1;??ng the .4 /
MIXED procedures of SAS (SAS Inst. Inc, Cary, NC) for a randomized complete block
design. Pig served as the experimental unit. The model included the fixed efi'ects of the
factorial treatments, their interaction, replication, and block by initial weight. Litter J .51-1*”?!

«kw? ‘Lobe —Q "U

within replication wasspecified as a random efi‘ectf All means presented are least square
means. Differences were considered significant at the level of P < 0.05.
Results and Discussion

Nutrient Content of Pork. Dietary nutrient composition altered the B-vitamin
content of the LDM (Table 9). Supplement withdrawal decreased the LDM riboflavin and
niacin concentrations (P < 0.01), but not thiamin. Feeding 30% wheat middlings during
the growing-finishing period increased LDM thiamin, riboflavin, and niacin (P < 0.04)
concentrations.

Contrary to the findings of our study, Patience and Gillis (1996) fed wheat-barley-
canola meal-based diets and observed that removing the vitamin premix 35 (1 prior to
slaughter reduced LDM thiamin. Riboflavin and niacin concentrations were numerically
but not significantly decreased by vitamin premix removal. Inconsistency of results may
be attributed to barley grain and canola meal, which, unfike corn, are rich sources of
riboflavin and available niacin, thus lessening the need to draw upon riboflavin and
niacin muscle reserves to satisfy metabolic demands during supplement withdrawal.
Patience and Gillis analyzed 15 LDM samples for vitamin content. We analyzed 62 LDM
samples, increasing the power of the test and decreasing the probability of type II

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45

Results from poultry studies indicate that removing supplemental riboflavin fi'om
broiler diets for 7 and 14 d decreases pectoralis major bioavailable riboflavin by 22 and
43%, respectively (Patel et al., 1997). A 21 d vitamin withdrawal period decreased p.
major total thiamin and niacin concentrations by 45 and 31%, respectively (Deyhim et al.,
1996). Standard practice is to slaughter broilers at 9 weeks of age. Broilers at six, seven,
and eight weeks of age typically weigh 59, 73, and 87% of their slaughter weight,
respectively (NRC, 1994). At the initiation of the supplement withdrawal period, the pigs
in our study weighed 76% of their slaughter weight.

Previous swine research supports that there is a general relationship between the
thiamin concentrations of the diet and skeletal muscle. Miller and coworkers (1943) fed
diets containing 2.9, 7.6, and 12.7 mg/kg of thiamin for 100 d prior to slaughter.
Increasing thiamin intake from 2.9 to 7.6 mg/kg and fi'om 7.6 to 12.7 mg/kg increased
loin thiamin concentrations by 110% (0.95 :t 0.21 to 2.00 i 0.44 mg/ 100g) and 15% (2.00
:t 0.44 to 2.31 :t 0.51 mg/ 100g), respectively. Pence and associates (1945) supplemented
finishing diets with 50 mg/d of thiamin for 8, 15, 22, 35 or 155 d prior to slaughter. Loin
thiamin concentrations increased with lengthened periods of supplementation up to 35 d
prior to slaughter. In our study, 30% wheat middling inclusion increased the thiamin
content of the diet by 1.8 to 2.6 mg/kg. The late finishing vitamin premix provided 1 mg
of thiamin/kg of feed. This explains why wheat middling inclusion significantly
influenced LDM thiamin concentrations while supplement withdrawal did not.

Like thiamin, dietary niacin is strongly correlated to pork niacin concentrations.
Christensen and associates (1943) increased the niacin content of pork fi'om 4.66 to 7.35

mg/ 100g by feeding 100 mg/d of supplemental niacin to growing and finishing pigs. In

46

[TEN

our study, the pigs receiving 30% wheat middlings received an additional 146 mg/d of
dietary niacin, increasing LDM niacin concentration fi'om 4.94 to 7.64 mg/ 100g.
Supplement withdrawal decreased dietary niacin by 27 mg/d, decreasing LDM niacin
from 7.25 to 5.32 mg/ 100g. Although NRC (1998) states that the niacin in wheat is
totally unavailable, this data indicates that a large portion of the niacin in wheat
middlings is bioavailable to the pig.

Dietary riboflavin concentrations influence muscle riboflavin content, but to a
lesser extent than other B-vitamins. Ittner and Hughes (1941) found that increasing
dietary riboflavin supplementation fiom 0 to 6 mg/d increased loin riboflavin
concentrations from 0.14 to 0.25 mg/lOOg. However, when doubling supplementation to
12 mg/d, loin riboflavin remained at .26 mg/ 100g. Miller and coworkers (1943) observed
no diflerence in loin riboflavin concentrations when feeding diets containing 3.68 to 5.44
mg/kg, confirming that the LDM approaches saturated storage capacity at 0.23 mg/ 100g.
In our study, LDM riboflavin concentrations steadily increased as the dietary
concentration increased from 1.2 to 3.6 mg/kg.

Supplement withdrawal did not affect the LDM Ca or trace mineral
concentrations, but decreased LDM P (P < 0.05). Wheat middling inclusion decreased
LDM concentrations of Cu (P < 0.03), but not Ca, Fe, P, or Zn. All late finishing diets
contained Cu, Fe, Mn, and Zn in excess of the estimated requirements (NRC, l998),for
optimal growth with the exception of Zn in the CSBM withdrawal diet, which was
approximately 30% below NRC (1998) recommendations.

Similarly, Edmonds and Arentson (2001) reported that removing vitamin and

trace mineral premixes fi'om finishing diets either 6 or 12 wk prior to slaughter did not

47

 

afl‘ect LDM Zn, Cu, or Fe concentrations. However, both 6 and 12 wk withdrawal
reduced Cu concentrations in the ham The trace mineral concentration of pork is
relatively consistent regardless of dietary concentrations (Leonhardt and Wenk, 1997).
Muscle Zn concentrations are maintained during times of deficiency (Bentley and Grubb,
1991; O’Leary et al., 1979). Muscle Cu concentrations are not affected by dietary
deficiencies (Ledoux et al., 1989) or excesses (Zanardi et al., 1998; Lauridsen et al.,
2000). An exception to the lack of variation of the mineral content of meat may be Fe.
Injecting growing pigs with 1600 mg of Fe IM from Fe-dextran during the nursery and
growing phases increased ham Fe concentrations by 21% (Henry et al., 1961), and
increasing dietary Fe from 62 to 209 mg/kg for 13 weeks increased LDM Fe
concentrations by 38% (Miller et a1, 1994).

The reduced LDM P caused by supplement withdrawal in our study indicates that
during periods of modest Ca and P deficiencies the pig draws upon muscle P reserves to
increase serum P and meet metabolic needs. Nicodemo et al. (1998) fed pigs diets
containing high supplementation (.86% Ca and .56% P), intermediate supplementation
(6.0% Ca and .4% P), or low supplementation (3.9 % Ca and 2.5% P). After 56 d on trial,
plasma Ca concentrations did not difi‘er between dietary treatments, but low
supplementation considerably reduced plasma P concentrations. Other studies found that
serum and plasma P concentration are reduced during periods of extreme (Howe and
Beecher, 1983; Koch and Mahan, 1985) but not moderate (Carter et al., 1996) dietary P
deficiencies. Thus, during periods of mineral deficiencies the pig may rely upon

secondary P reserves such as muscle to sustain adequate circulating P concentrations.

48

Pork Oxidative Stability. Supplement withdrawal did not decrease LDM vitamin
E concentrations (Table 9). O’Sullivan et al. (1997) found that feeding 0 vs 20 mg DL-a-
tocopheryl acetate/kg feed for 130 d prior to slaughter did not affect LDM vitamin E
concentrations. In contrast, Dove and Ewan (1991) reported that deleting supplemental a-
tocopheryl acetate from pig diets for 13 weeks prior to slaughter reduced LDM a-
tocopherol concentrations by 82% (1.035 vs 0.185 ug/g). Likewise, Edmonds and L
Arentson (2001) reported that removing vitamin and trace minerals for 6 weeks pre-

slaughter decreased LDM vitamin E concentrations by 77%. While withdrawal times and i '-

 

premix vitamin E concentrations differed between our study and the Edmonds and
Arentson report, the vitamin E analyses were performed by the same laboratory using the
same methods.

Supplementing 100 to 200 mg/kg of dietary a-tocopherol for extended periods of
time has been reported to increase muscle a-tocopherol concentrations and decrease lipid
oxidation as measured by thiobarbituric acid reactive substances (TBARS) (Monahan et
al., 1990ab, 1992; Asghar et al., 1991ab; Cannon et al., 1996; Jensen et al., 1997;
Lauridsen et al., 2000). In our study we did not conduct a TBARS assay because of the
assay’s high inherent variability. We anticipated that removing only 11 mg/kg of dietary
a-tocopherol for 28 (1 would not sufliciently decrease LDM vitamin E concentrations to
elicit a measurable increase of TBARS.

Wheat middling inclusion increased LDM vitamin E concentrations. However,
laboratory analyses found that the diets containing wheat middlings had lower vitamin E
concentrations than the diets not containing wheat middlings. Additional choice white

grease was added to the CSBM+WM diets to balance diets for MB. This observation

49

suggests that the vitamin E in either the choice white grease or the wheat middlings may
be more bioavailable than the supplemented vitamin E. Zanardi et al. (1998) reported that
adding 6% dietary sunflower oil, though increasing total dietary vitamin E by 27 mg/kg,
had a much greater influence on LDM vitamin E concentrations than 200 mg/kg of
supplemental a-tocopheryl acetate.

Dietary treatment did not affect the activity of the LDM antioxidative enzymes
Cu/ZnSOD and GPX. Previous research with 4 to 9 week-old weanling pigs shows that.3
mg/kg of supplemental dietary Se is necessary to maintain muscle GPX activity (Lei et
al., 1998). Our study shows that this is not the case with finishing pigs. In agreement with
our study, previous research has shown that removing supplemental Cu fi'om the diets of
growing pigs (Lauridsen et al., 1999) and rats (Paynter et al., 1979) does not affect
Cu/ZnSOD activity in skeletal muscle. The analyzed concentrations of Cu of the
withdrawal diets were 124 to 204% of the NRC (1998) estimated requirement, and the
calculated Se concentrations of the withdrawal diets were 70 to 201% of the NRC
estimated requirement.

Growth Performance and Carcass Characteristics. Supplement withdrawal did
not affect growth performance as measured by ADG, ADFI, and gainzfeed (Table 10), or
carcass traits as measured by backfat depth, LEA, and dressing percentage (Table 11).
These data agree with previous studies (Patience and Gillis, 1995, 1996; Kim et al., 1997;
Mavromichalis et al., 1999; McGlone, 2000; Edmonds and Artentson, 2001) in which
withdrawing vitamin and/or mineral supplementation for 17 to 45 d prior to slaughter did

not afl’ect growth and carcass traits.

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Wheat middling inclusion did not afl'ect growth performance with the exception
of ADG during the growing phase. Growth performance was not affected by lesser wheat
middling inclusion rates (5 to 15%) during the nursery phase and 30% wheat middling
inclusion during the early and late finishing phases.

Previous research (Patience et al., 1977) reported that a maximum of 20% wheat
middlings can be included in growing diets before decreasing grth performance, while
others found that inclusion rates of 30% (Young, 1980; Erickson et al., 1985) did not
decrease growth. Cromwell et al. (1992) reported that when wheat middlings with a light
bulk density are used, growth performance of growing-finishing pigs decreased linearly
as the amount of wheat middlings increased. Wheat middlings with a heavy bulk density
could constitute 20 to 40% of the ration without substantially afl‘ecting performance. The
bulk density of the wheat middlings used in our study was 387.4 g/L, much heavier than
the average wheat middling bulk density of 320 g/L as reported by Cromwell et al.
(2001). The observed decrease in ADG during growing phase may reflect that these pigs
had a higher lean gain potential than pigs used in previous research studies, thus requiring
a more nutrient-dense ration

Nutrient Excretion. As presented in Table 12, dietary mineral concentrations
influenced nutrient excretion. There was a statistical interaction between the main effects
of supplement withdrawal and wheat middling inclusion. In diets containing full vitamin
and mineral supplementation, wheat middling inclusion reduced fecal Ca, Cu, Fe, and Zn
concentrations (P < 0.01) and increased fecal Mn (P < 0.01).

Supplement withdrawal reduced fecal P excretion by 20% and trace mineral

excretion by 59 to 78% (P < 0.01). These decreases are noteworthy when considering that

the market hog consumes approximately one-third of its total lifetime feed intake during
the final 4 wk prior to slaughter, thus producing approximately one-third of its total fecal
excretion. Michal and Froseth (1999) and O’Quinn et al. (1997) observed 40% and 12%
decreases in P excretion, respectively, when deleting inorganic P fiom barley-pea and
sorghum-soybean meal-based finishing diets, respectively.
Implications

The concentrations of many vitamins and minerals in pork are influenced by
premix inclusion and the choice of primary feed ingredients utilized in ration
formulation. Supplement withdrawal does not affect growth perfornmnce or carcass traits
and decreases nutrient excretion, making it an attractive practice to pork producers.
However, it also decreases the nutrient content of pork and may diminish consumer

perception of the healthiness of pork.

55

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56

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59

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60

CHAPTER 4. EFFECTS OF SUPPLEMENT WITHDRAWAL AND WHEAT
MIDDLING INCLUSION ON BONE METABOLISM, BONE STRENGTH, AND
INCIDENCE OF BONE FRACTURES OCCURING AT SLAUGHTER.

A paper to be published in the Journal of A nimal Science
D. T. Shaw, D. W. Rozeboorrr, G. M. Hill, M. W. Orth, D. S. Rosenstein and J. E. Link.
Department of Animal Science, Michigan State University, East Lansing, 48824
Abstract

The objective of this study was to determine if supplement withdrawal (omission of
dietary vitamin and trace mineral premixes and 2/3 reduction of inorganic P) 28-d pre-
slaughter affects bone metabolism, bone strength, and the incidence of bone fiactures at
slaughter. The effect of adding either 0 or 30% wheat middlings to com-soybean meal-
based growing and finishing diets was also evaluated. Crossbred pigs (n = 62) were
assigned to one of four treatments in a 2 x 2 factorial design (with or without supplement
withdrawal, 0 or 30% wheat middlings). Serum was collected on d O, 14, and 27 of the
withdrawal period to determine changes in the concentrations of osteocalcin, an indicator
of osteoblast activity, and pyridinoline, an indicator of collagen degradation. The serum
osteocalcin and pyridinoline concentrations on d 14 and d 27 were analyzed as change
from the d 0 concentration. At slaughter, radiographs of the lumbar vertebrae and of the
right and left femurs were taken to determine the incidence of bone fi'actures. Third
metacarpal bones were analyzed for bone mineral density, peak load, ultimate shear
stress, and percent ash. Removing dietary supplements increased the change of serum
osteocalcin and pyridinoline concentrations, indicating an increase in osteoblast activity
and bone resorption (P < 0.05). Supplement withdrawal decreased the bone mineral

density, peak load, ultimate shear stress, and percent ash of the metacarpal bones (P <

0.01 ). Dietary wheat middling inclusion did not alter bone quality. Neither supplement
withdrawal nor wheat middling inclusion affected the incidence of bone fiactures at
slaughter. The results of this study indicate that supplement withdrawal increases bone
turnover and decreases bone quality.
Introduction

The dietary Ca and P concentrations necessary to maximize growth performance
in growing-finishing pigs are well defined (NRC, 1998). However, maximum bone
mineralization and bone strength require higher dietary Ca and P concentrations than is
required to maximize growth performance (Crenshaw et al., 1981; Maxson and Mahan,
1983; Combs et al., 1991). It is not known if increased mineralization reduces the
likelihood of bone fractures occurring during the slaughtering process.

In recent years, there has been increased interest in minimizing P in finishing pig
diets to reduce nutrient excretion and feed costs. Previous research (O’Quinn et al., 1997;
Mavromichalis et al., 1999; Shaw et al., 2001) has indicated that minimal dietary
inorganic P additions are necessary during the late finishing phase to maintain growth
performance and carcass quality. During this period, the animal may draw upon mineral
body reserves found in the bone and other tissues to support metabolic requirements that
are not met by the diet. Consequently, bone strength is decreased (O’Quinn et al., 1997).
However, it is currently unknown if reducing dietary mineral additions prior to slaughter
alters bone metabolism and decreases bone strength to the extent of increasing the
incidence of bone fiactures occurring at slaughter.

The objectives of this study were to determine the effect of supplement

withdrawal (omission of vitamin and trace mineral premixes and 2/3 reduction of

62

inorganic phosphorus) for 28 d prior to slaughter on bone metabolism, bone strength, and
incidences of bone fi'actures occurring at slaughter. Furthermore, this research evaluated
the influence of dietary wheat middling inclusion on the same parameters.

Materials and Methods

The experimental design, dietary treatments, and management of the pigs utilized
in this study have been reported previously (Shaw et al., 2001). In summary, 62 crossbred
barrows were individually penned and fed com-soybean meal-based grow-finish diets
containing either 0 (CSBM) or 30% (CSBM+WM) wheat middlings. During the final 28
d before slaughter, 31 pigs were fed supplement withdrawal diets. The Ca to available P
ratio was maintained at 2.5:] in all late finishing diets.

On (I 0, d 14, and d 27 of the withdrawal period, blood was collected from each
pig by venapuncture from the anterior vena cava into 10 m1. vacutainer tubes with 20
gauge, 1‘/2 inch needles. Blood was centrifuged at 4° C, 3,000 x g, for 15 min (Beckman
GS-6KR, Palo Alto, CA). Serum was collected into polypropylene tubes and stored at -
80° C until osteocalcin and pyridinoline assays were performed.

Twenty-eight days after the initiation of the late finishing diets and at an average
live weight of 103.4 kg, pigs were transported to the Michigan State University Meat
Laboratory for slaughter. No visible indications of bone fi'actures were observed
preslaughter. Pigs were electrically stunned (110 volts, 420 amps, 3 sec.), hoisted by
chain from the right leg, and exsanguinated. Following scalding, pigs were mechanically
dehaired (approximately 60 sec.) and the remaining hair and feet were manually

removed. Pigs were eviscerated and the carcasses were split along the spinal colurrm.

63

Radiographs. Following evisceration and prior to splitting the spine, a
ventrodorsal projection radiograph of the lumbar vertebrae was taken (80 KVp, 17 mA,
.18 sec., 30 cm focal film distance) of each carcass using a portable radiograph machine
(Minxray, Northbrook, IL). Following the splitting of the spine, radiographs were taken
(75 KVp, 17 mA, .12 sec., 30 cm focal film distance) of the right and left femurs,
including the femoral heads. Radiographs were examined by a radiologist for incidence
of bone fractures.

Computed Tomography. Bone mineral density of the third metacarpal of the right
foot (MC 111) was examined by x-ray-conrputed tomography (CT scan). Excised feet
were placed on the CT table (CT 9800, GE Medical Systems, Milwaukee, WI) in palmar
recumbency. A scout view was taken to determine mid-shait location and a cross-
sectional image was then acquired through the transverse plane. The pad on which each
foot was placed contained three hydroxyapatite standards. The standards served as
internal controls for each CT image to account for x-ray energy fluctuations that may
occur between images. The bone mineral density of the MC 111 was determined by
comparison of the x-ray linear attenuation coefficient of the bone to that of the
hydroxyapatite standards. Total and cortical cross-sectional area were estimated by
tracing the endosteal and periosteal margins of the MC III. Area within the outlined
region and bone mineral density were estirmted when recorded images were analyzed
with a bone mineral density software package.

Bone characteristics. The MC 111 bones were cleaned of all muscle and
connective tissue with a scalpel. Peak force and ultimate shear stress of the MC 111 was

determined with an Instron Universal Testing Machine (Model 4202, Instron, Canton, .

MA) fitted with a 20 kN load cell and that moved at a test speed of 5.0 min/min
according to the procedure described by Combs et al. (1991). The shape of the cross-
sectional area of the bone tissue was assumed to be that of an elliptical quadrant and area
was calculated using the following equation:

V4 * 1t * (B* D—b*d)+d* (B—b)/2+b* (D—d)/2
Where B is the outside major diameter, b is the inside major diameter, D is the outside
minor diameter, and d is the inside minor diameter. Ultimate shear stress was calculated
according to the following equation (ASAE, 1999): stresss = Ultimate load/2 x Area.

The same bones that were mechanically tested were wrapped in cheesecloth and
extracted with ethyl ether using a Soxhlet apparatus for 72 h. Bones were dried at 100°C
for 12 h to determine the dry fat-flee weight, placed in crucibles, then ashed in a muffle
firmace for 16 h at 500°C. Percent ash was calculated as a percentage of the dry fat-fi'ee
weight.

Mineral Analysis. The ashed MCIII bones were prepared for mineral analysis by
nitric acid wet digestion. Samples were transferred to Phillips beakers and the crucibles
were rinsed twice with 10 mL nitric acid (70%). Samples were digested in 30 mL of '
nitric acid with heat, and then rehydrated to 100 mL with .5% nitric acid. Calcium
concentrations were determined by flame atomic absorption spectrophotometry (Smith-
Heiftje 4000, Thermo Jarrell Ash Corporation, Franklin, MA), and P concentrations were
determined using DU 7400 spectrophotometer (Beckman, Palo Alto, CA). Bone mineral
concentrations were calculated as the percentage of the dry fat-free weight.

Osteocalcin Assay. Serum osteocalcin concentrations were determined in

duplicate using commercially available ELISA tests (N ovocalcin; Metra Biosystems,

65

Mountain View, CA) according to the manufacturer’s instruction (Catalog number 8002,
Metra Biosystems, Mountain View, CA). The antibody employed in the osteocalcin assay
recognizes only the intact osteocalcin produced by osteoblasts and not the osteocalcin
fi'agments fi'om resorbed bone. Consequently, the analyzed serum osteocalcin
concentrations are a reflection of osteoblast activity specifically, and not bone turnover.

Pyridinoline Assay. Serum pyridinoline concentrations were determined in
duplicate using commercially available ELISA tests (Serum Pyd; Metra Biosystems,
Mountain View, CA) according to the manufacturer’s instruction (Catalog number 8019,
Metra Biosystems, Mountain View, CA). This assay demonstrates high aflinity for fi'ee
pyridinoline and negligible binding to deoxypyridinoline and pyridinoline and
deoxypyridinoline peptides, reducing variability in estimating collagen degradation.

Statistical Analysis. All data were analyzed by least squares AN OVA using the
MIXED procedures of SAS (SAS Inst. Inc., Cary, NC) for a randomized complete block
design. Pig served as the experimental unit. The model included the fixed efl‘ects of the
factorial treatments, their interaction, replication, and block by initial weight. Litter
within replication was specified as a random efl‘ect. All means presented are least square
means. Difl‘erences were considered significant at the level of P < 0.05.

Results and Discussion

Analysis of Diets. The analyzed Ca concentrations of Diets 1 to 4 were .68, .67,
.38, and .61%, and the total P concentrations were .45, .55, .34, and 52%, respectively.
The resulting Ca to total P ratios were 1.51, 1.22, 1.12, and 1.17 for treatments 1 to 4,
respectively. A suggested Ca to total P ratio for com-soybean meal-based diets is

between 1:1 and 1.25:1 (NRC, 1998).

66

Bone Metabolism. Because initial osteocalcin and pyridinoline concentrations
were statistically different between dietary treatments, the d 14 and d 27 values were also
analyzed as deviation from the d 0 concentration. Supplement withdrawal, but not wheat
middling inclusion, increased serum osteocalcin concentrations on d 14 and d 27 of the
withdrawal period (Table 13). Similar responses have been noted in other swine studies.
Carter et al. (1996) observed that serum osteocalcin concentrations linearly decreased as
dietary Ca decreased fiom 1.14 to .42% and dietary P decreased from .95 to .35% over a
30 d period. Eklou-Kalonji et al. (1999) found in a 30 d trial that reducing of dietary Ca
from .90 to either .38 or .11% increased serum osteocalcin in growing and finishing pigs.
Studies with rats have also concluded that serum osteocalcin concentrations are inversely
correlated with dietary Ca and/or P content (Lian et al., 1987; Tanimoto et al., 1991,
Harnalainen, 1994).

Serum osteocalcin, and therefore osteoblast activity, may be increased during
dietary mineral deficiencies because of increased mechanical loading on the bone cells.
Decreased mineralization of the bone surfaces increases the mechanical stress on
individual cells of the bone matrix. Osteoblasts sense changes in matrix deformation and
increase their activity.

Not all studies have concluded that decreased dietary mineral supplementation
increases serum osteocalcin concentrations. Nicodemo et al. (1998) found that decreasing
dietary Ca fi'om .86 to .39% for 8 wk did not alter serum osteocalcin in growing pigs.
Also, Hillman and coworkers (1993) did not observe differences in serum osteocalcin
when neonatal pigs were fed diets containing excess, normal, or deficient Ca and P for 28
d.

67

 

 

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In our study, supplement withdrawal, but not wheat middling inclusion, increased
the change in serum pyridinoline concentration on d 14 and d 27 of the withdrawal
period. Few published reports identify the relationship between serum pyridinoline and
dietary mineral intake. Studies with rats (Egger et al., 1994) and humans (Garnero et al.,
1994; Shapses et al., 1995; Shen et al., 1995) reported that urinary pyridinium excretion
was inversely proportional to dietary calcium concentration.

Bone measurements. As shown in Table 14, supplement withdrawal decreased
total bone mineral density, cortical bone mineral density, peak force, shear stress, percent
bone ash, and the Ca and P concentrations of the MC III (P < 0.04). This indicates that
bone resorption exceeded bone formation. Increased bone resorption caused by
supplement withdrawal is reflected by the change of serum pyridinoline fiom d 0 to d 14
and from d 0 to d 27 rather than the analyzed d 14 and d 27 concentrations. Therefore,
adjusting serum pyridinoline to reflect change over time appears to be an appropriate data
modification.

Several nutrients that contribute to bone quality were decreased in diets where
supplements were withdrawn. In swine studies, bone strength is decreased in pigs during
moderate dietary restriction of Ca (O’Quinn et al., 1997; Nicodemo et al., 1998; Eklou-
Kalonji et al., 1999) and P (Carter et al., 1996; Hall et al., 1991). Furthermore, dietary
vitamin A (Zile et al., 1973), vitamin D (Sinha et al., 1988), vitamin K (Knapen et al.,
1993), and Zn (Miller et al., 1968) are essential to maintain bone quality and were present
below NRC (1998) suggested minimum concentrations in one or both of the supplement

withdrawal diets.

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70

Bone fiactures. While supplement withdrawal decreased metacarpal bone quality,
no femoral or vertebral fractures were observed in this study. It was observed that one
pig, which received a fully supplemented CSBM diet, had a broken right tibia following
hoisting by the clmin.

Pond and others (1969) reported that the vertebrae and the proximal and distal
ends of the femur are depleted of mineral before the mid-diaphyseal region of the long
bones in young pigs. Crenshaw and associates (1981) reported that decreasing bone
quality in the metacarpals parallels decreasing bone quality of the vertebrae and femoral
bones in growing and finishing pigs. Although no bone fractures were observed in the
radiographic films, the decreased bone mineralization of the MC 111 indicates that the
pigs were at increased risk for vertebral and femoral fiactures.

Dritz et al. (2000) described a case study in which a processor reported that the
incidence of minor loin damage of pigs from a single farm was greater than twice that of
pigs received fiom other producers. Most of the loin damage was reportedly caused by
vertebral fiactures occurring during the stunning process. Dietary available P of pigs
weighing 95 to 109 kg and 109 kg to market was increased from approximately 4.4 and
3.2 g/d, respectively, to 5.7 and 4.8 g/d. After a two-month transition period, the
incidences of minor loin damage dropped to that of pigs fi'om other producers.

In the present study, 31 pigs were fed supplement withdrawal diets. Because
wheat middlings are naturally high in P, only the 15 pigs fed CSBM supplement
withdrawal diets received dietary Ca and P concentrations below the suggested NRC
(1998) minimum requirements. Assuming that the industry average for loin damage

caused by vertebral fiactures approaches the .58% reported by Dritz and coworkers, it is

71

 

not surprising that we did not observe vertebral and femoral fractures in the present
study. Furthermore, differences in livestock handling and slaughter procedures between
commercial and university conditions decreased the likelihood bone fi'acture occurrence
in this study.
Implications

Supplements should not be withdrawn from potential breeding animals so that
sow longevity is maintained. Because of the relationship between dietary vitamins and
minerals concentrations and bone metabolism, determination to practice supplement
withdrawal should include consideration of the bone quality and its effect on carcass
value. It still remains to be determined if supplement withdrawal increases the incidence

of bone fractures occurring at slaughter.

72

Literature Cited

ASAE. 1999. ASAE standards: standards, engineering practices and data adopted by the
American Society of Agricultural Engineers. St. Joseph, MI.

Carter, S. D., G. L. Cromwell, T. R. Combs, G. Colombo, and P. Fanti. 1996. The
determination of serum concentrations of osteocalcin in growing pigs and its relationship
to end-measures of bone mineralization. J. Anim. Sci. 74:2719-2729.

Combs, N. R., E. T. Komegay, M. D. Lindemann, D. R. Notter, J. H. Wilson, and J. P.
Mason. 1991 . Calcium and phosphorus requirement of swine fi'om weaning to market

weight: 11. Development of response curves for bone criteria and comparison of bending
and shear bone testing. J. Anim. Sci. 69:682-693.

Crenshaw, T. D., E. R. Peo, A. J. Lewis, B. D. Moser, and D. Olson. 1981. Influence of
age, sex and calcium and phosphorus levels on the mechanical properties of various
bones in swine. J. Anim. Sci. 52:1319-1329.

Dritz, S. S., M. D. Tokach J. M. Sargeant, R D. Goodband, and J. L. Nelssen. 2000.
Lowering dietary phosphorus results in a loss in carcass value but not decreased growth
performance. Swine Health Prod. 8:121-124.

Egger, C. D., R. C. Muhlbauer, R. Felix, P. D. Delmas, S. C. Marks, and H. Fleisch.
1994. Evaluation of urinary pyridinoline crosslink excretion as a marker of bone
resorption in the rat. J. Bone Miner. Res. 9:1211-1219.

Eklou-Kalonji, E., E. Zarath, C. Colin, C. Lacroix, X. Holy, 1. Denis, and A. Pointillart.
1999. Calcium-regulating hormones, bone mineral content, breaking load and trabecular
remodeling are altered in growing pigs fed calcium-deficient diets. J. Nutr. 129:188-193.

Garnero, P., W. J. Shih, E. Gineyts, D. B. Karpf, and P. D. Delmas. 1994. Comparison of
new biochemical markers of bone turnover in late postmenopausal osteoporotic women
in response to alendronate treatment. J. Clin. Endocrinol. Metab. 79:1693-1700.

Hall, D. D., G. L. Cromwell, and T. S. Stahly. 1991. Effects of dietary calcium,
phosphorus, calciumzphosphorus ratio and vitamin K on performance, bone strength and
blood clotting status of pigs. J. Anim. Sci. 69:646-655.

Harnalainen, M. M. 1994. Bone repair in calcium—deficient rate: Comparison of xylitol +
calcium carbonate with calcium carbonate, calcium lactate and calcium citrate on the
repletion of calcium. J. Nutr. 124:874-881.

Hillman, L., L. Meyer, J. Saunders, C. Foster, K. Zinn, D. Ledoux, and T. Veum. 1993.

Effect of dietary calcium and phosphorus on mineral homeostasis, bone mineralization
and calcium absorption in the neonatal pig model. J. Bone Miner. Res. 8:8292 (Abstr.).

73

Knapen, M. H. J., K S. G. Jie, K. Hamulyak, and C. Vermeer. 1993. Vitamin K-induced
changes in markers for osteoblast activity and urinary calcium loss. Calcif. Tissue Int.
53:81-85.

Lian, J. B., Cames, D. L., and M. J. Glimcher. 1987. Bone and serum concentrations of
osteocalcin as a function of 1,25-dihydroxyvitamin D3 circulating levels in bone disorders
in rats. Endocrinol. 120:2123-2130.

Mavromichalis, I., J. D. Hancock, 1. H. Kim, B. W. Senne, D. H. Kropf, G. A. Kennedy,
R. H. Hines, and K. C. Behnke. 1999. Effects of omitting vitamin and trace mineral
premixes and(or) reducing inorganic phosphorus additions on growth performance,
carcass characteristics, and muscle quality in finishing pigs. J. Anim. Sci. 77:2700-2708.

Maxson, P. F., and D. C. Malian 1983. Dietary calcium and phosphorus levels for
growing swine fi'om 18 to 57 kilograms body weight. J. Anim. Sci. 56:1124-1134.

" H.152. .m-

Miller, E. R., R. W. Luecke, D. E. Ullrey, B. V. Baltzer, B. L. Bradley, and J. A. Hoefer.
1968. Biochemical, skeletal and allometric changes due to zinc deficiency in the baby
pig. J. Nutr. 95:278-286.

 

Nicodemo, M. L. F., D. Scott, W. Buchan, A. Duncan, and S. P. Robins. 1998. Effects of
variations in dietary calcium and phosphorus supply on plasma and bone osteocalcin
concentrations and bone mineralization in growing pigs. Exp. Physiol. 83:659-665.

NRC. 1998. Nutrient Requirements of Swine. 10th ed. National Academy Press,
Washington, DC.

O’Quinn, P. R., D. A. Knabe, and E. J. Gregg. 1997. Digestible phosphorus needs of
terminal-cross growing-finishing pigs. J. Anim Sci. 75:1308-1318.

Pond, W. G., F. E. Lovelace, E. R. Walder, and L. Krook. 1969. Distribution of
parenterally administered “Ca in bones of growing pigs. J. Anim Sci. 29:298-302.

Shapses, S. A., S. P. Robins, E. I. Schwartz, and H. Chowdhury. 1995. Short-term
changes in calcium but not protein intake alter the rate of bone resorption in healthy
subjects as assessed by urinary pyridinium cross-link excretion. J. Nutr. 125:2814-2821.

Shaw, D. S., D. W. Rozeboom, G. M. Hill, A. M. Booren, and J. E. Link. 2001. Effects of
supplement withdrawal and wheat middling inclusion on the nutrient content of pork,
pork oxidative stability, and nutrient excretion. Companion paper. Chapter 3.

Shen, V., R. Birchman, R. Xu, R. Lindsay, and D. W. Dempster. 1995. Short-term

changes in histomorphometric and biochemical turnover markers and bone mineral
density in estrogen and/or dietary calcium-deficient rats. Bone. 16:149-156.

74

Sinha, R., J. C. Smith, Jr., and J. H. Soares, Jr. 1988. Calcium and vitamin D in bone
metabolism: Analyses of their efiects with a short-term in vivo bone model in rats. J.
Nutr. 118:99-106.

Tanimoto H., K. H. W. Lau, S. K Nishirnoto, J. E. Wordegal, and D. J. Baylink. 1991.
Evaluation of the usefulness of serum phosphatases and osteocalcin as serum markers in
a calcium depletion-repletion rat model. Calcif Tissue Int. 48:101-110.

Zile, M., H. Ahrens, and H. F. DeLuca. 1973. Vitamin A and bone metabolism in the rat.
J. Nutr. 103:308-313.

75

APPENDIX

76

APPENDIX A
Supplement Withdrawal Does Not Cause Blood Splash in Pork
Background

Blood hemorrhaging is a serious commercial problem and may occur in as much
as 10% of pork carcasses (Swatland, 1984). Capillaries may rupture during slaughter
causing small dark red areas to spread over the meat surface. During and afier stunning,
blood pressure escalates as the heart continues to pump; the muscles contract,
constricting the capillaries, ofien causing the capillaries to rupture (Romans et al., 1994).
Blood hemorrhage also occurs when violent muscular contractions tear the muscle tissue,
resulting in hemorrhages that appear along muscle seams (Warrington, 1974).

The occurrence of blood hemorrhages can be reduced with proper stunning.
Stunning pigs with either higher voltage or higher frequency electricity for a shorter
period of time decreases the incidence of muscle hemorrhages (Warrington, 1974).
Decreasing the time from stunning to sticking relieves blood pressure and also decreases
the chance of capillary rupture (Romans et al., 1994).

Bone fi'actures are a third cause of muscle hemorrhages. Dritz et al. (2000)
describe a case study of minor vertebral fiactures causing minor loin damage. The
authors proposed that inadequate dietary available P sufliciently decreased skeletal
integrity to increase the incidences of loin damage. Dietary available P of pigs weighing
95-109 kg and 109 kg to market was increased from approximately 4.4 and 3.2 g/d,
respectively, to 5.7 and 4.8 g/d. After a two-month transition period, the incidences of

minor loin damge dropped to that of pigs fi'om other producers.

77

Description

The experimental design, dietary treatments, and management of the pigs utilized
in this study are presented in chapters 3 and 4. After fabricating the carcasses of the first
replication of pigs, the Meat Lab stafl notified the investigators that the frequency of
intramuscular blood splash was 40 to 50%, much higher than that of previous pigs killed
at the facility. This blood splash differs from the extramuscular loin damage reported by
Dritz et al. (2000), which was likely caused by vertebral fi'actures. In the present study,
no vertebral fiactures were observable in the radiographic film. Therefore, we
investigated if supplement withdrawal increases intramuscular blood splash by observing
the carcasses of the pigs from the second replication.

Digital pictures were taken of the fabricated loin, shoulder, belly, and ham of each
carcass. The pictures from each carcass were categorically scored based on the amount

and the severity of blood splash as follows:

Score Description

1 No BS No signs

2 Slight BS Splash at seams g tissues — 1 muscle in 1 to 2 cuts

3 Moderate BS Splash at seams m tissues — multiple muscles in 1 to 2
cuts

4 Severe BS Splash at seams and tissues — multiple muscles in 3+ cuts

5 Excessive BS Splash throughout all tissues
There were insufficient carcasses (n = 30) for chi-square statistical analysis; therefore,

mean averages are provided in Table 15.

78

Table 15. Effect of dietary treatment on carcass blood splashab

 

 

Full supplementation Supplement withdrawal
CSBM Midds CSBM Midds
Score
1.0 1 1 3 2
1.5 2 O 2 2
2.0 3 6 0 2
2.5 1 0 1 l
3.0 0 l l 1
Mean 1.78 2.29 1.44 1.81

 

ItNo. of animals by treatment: CSBM and full suppl. (n = 7), CSBM+WM and full
suppl. (n = 8), CSBM and suppl. withdrawal (n = 7), CSBM+WM and suppl.
withdrawal (n = 8).

bIndicates the number of animals assigned each catgorical score.

79

Sixty percent of the carcasses contain at least slight blood splash, and 13%
contained moderate blood splash. No severe or excessive blood splash was found.
Neither supplement withdrawal nor wheat middling inclusion appeared to affect the
incidences of blood splash. The high incidences of blood splash may be due to error of
the electrical stunning mechanism or genetic disposition. These pigs were also the first
offspring of the Musculor x York sire line slaughtered at the MSU Meat Lab. Overall,
carcass quality was poor as the muscle was pale and watery. Similar carcass observations
were noted in Musculor-sired pigs that were later slaughtered in the MSU Meat Lab. In
addition to producing carcasses of poor quality, this genetic line may be susceptible to
blood splash.

Literature Cited
Dritz, S. S., M. D. Tokach, J. M. Sargeant, R. D. Goodband, and J. L. Nelssen. 2000.
Lowering dietary phosphorus results in a loss in carcass value but not decreased growth

performance. Swine Health Prod. 8:121-124.

Price, J. F ., and B. S. Schweigert. 1987. The Science of Meat and Meat Products. 3rd ed.
Food and Nutrition Press, Inc., Westport, CN.

Romans, J. R, W. J. Costello, C. W. Carlson, M. J. Greaser, and K W. Jones. 1994. The
Meat We Eat. 13th ed. Interstate Publishers, Inc., Danville, IL.

Swatland, H. J. 1984. Structure and Development of Meat Animals. Prentice-Hall Inc.,
Englewood Cliffs, NJ.

Warrington, R. 1974. Electrical stunning: a review of the literature. Vet. Bull. 44:617-
628.

80

 
    

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