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OCR for page 101
JOHN A. MARCHELLO and
WILLIAM H. HALE
Nutrition and Management
Aspects of Ruminant Animals
Related to Reduction of
Fat Content in Meat and Milk
As knowledge in the field of animal nutrition increased and as the feedlot
industry developed, more and more high-concentrate foodstuffs were
incorporated into ruminant rations. This was largely due to the avail-
ability of low-cost feed grains, which significantly improved efficiency
and led to increased monetary returns to the production units while
providing animal products, primarily meat and milk, that possessed
very high consumer acceptability. As the affluence of the consumer
increased, the demand for these high-quality animal products increased,
with the result that our entire animal production system is geared to
providing these products.
Because of the shortage of feed-grain supplies, a management system
that requires less grain input for feeding to ruminant animals must be
considered. It must be efficient and must provide products that have high
consumer acceptability.
For many years, our marketing scheme for meat and milk has been
based largely on the fat content of these products, because this was a
good indication of high quality. A carcass graded Choice must possess
a specified amount of intramuscular fat. Many times the result of this
requirement is that carcasses graded Choice have substantial amounts
of subcutaneous waste fat. Actually, all that is necessary is a small
amount of surface fat enough to protect the carcasses during handling,
storage, and cooking.
Since its inception, the milk-marketing system has been based on the
fat content of the milk. Therefore, any management procedure that
101
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102
MARCHELLO AND HALE
changes the fat content of milk directly influences the economics of the
marketing system.
This chapter will present a review of some of the research that has
been conducted to determine the effect of nutritional practices and
management systems on the composition of carcasses and milk. These
remarks will be concerned primarily with efforts to control fat content
and with how these efforts affect consumers' acceptance of meat and
milk.
As early as 1920, researchers were concerned with the composition
of gain in ruminant animals. Haecker (1920) designed a study to de-
termine the composition of gain from 47 kg to various weights up to
685 kg (Table 1 ) . The initial weight gain of 226 kg was predominantly
water (59%~; fat and protein increased about equally (17.2% and
19.3% ). If the total gain from 47 to 458 kg is considered, fat content
accounts for a third of the gain in weight. As the final animal weight
increased to 685 kg, fat accounted for about 40% of the gain.
In a similar study, Moulton et al. (1922) evaluated the composition
of gain from birth to 48 months of age. Cattle on three nutritional
regimes were considered: full-fed, fed for growth, and limited-fed
(Table 21. As the age of the animal increased, fat accounted for a
greater percentage of the gain in weight, regardless of nutritional
regime. The composition of the increase from birth to 3 months was
only 5% fat in the young, thin calf and had an energy content of only
1,734 kcal per kilogram of gain. The composition of the increase from
birth to 48 months was about 50% fat in the finished steer and had
an energy value in excess of 5,000 kcal per kilogram.
When the cattle were fed for limited growth or for minimal growth,
the weight gains were primarily increases in water. The contributions
of fat and protein to gain in these cattle were similar and increased
with advancing age; each accounted for about 20% of the gain from
birth to 48 months of age in the two groups of cattle.
Wanderstock and Miller (1948) evaluated the influences of five man-
agement systems on the carcass composition of fed steers (Table 31.
TABLE 1 Composition of Gain in Cattle a
From To Water Fat Protein
(kg) (kg) (%) (%) (%)
47 273 59.1 17.2 19.3
47 458 49.9 29.4 16.8
47 642 45.9 34.8 15.9
52 685 41.3 40.2 15.4
a Adapted from Haecker (1920) .
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Nutrition and Management Aspects of Ruminant Animals 103
TABLE 2 Percentage of Fat in Cattle of Various Weights on Three
Nutritional Regimes e
Percentage of Fat, by Nutritional Regime
Fed for Limited
Age (months) Full-Fed Growth Fed
3 12.8 10.2 5.1
8 19.4 22.7 13.2
11 24.4 17.9 16.4
18 30.0 16.3 11.5
40 48.3 22.2 1 1.4
48 45.8 26.7 18.6
{b SOURCE: Adapted from Moulton et al (1922).
These researchers used the 9-10-11 rib cut to establish the physical
composition of the steers. Large differences in total fat content were
noted among the groups on the various nutritional regimes, even though
the cattle were fed to similar weights before slaughter.
Carcasses from the pasture-fed (no grain) cattle had the least amount
of fat and graded the lowest. Cattle fed on pasture for a short time
and then full-fed yielded carcasses that were leaner than those of cattle
on the other nutritional regimes, with the exception of the pasture-fed
cattle. On the basis of palatability studies, the investigators concluded
that beef produced by feeding grain on pasture, after pasturing, or after
feeding in drylot was more acceptable to the consumer than that
produced by finishing on pasture alone. Meat cuts from the pasture-
only cattle were significantly less desirable in palatability and in overall
appearance than cuts from the other cattle.
TABLE 3 Physical Analyses Data of the 9-10-11 Rib Cut of Cattle
under Five Management Schemes a
Treatment b
Trait
Lot 1
Lot 2
Lot 3
Lot 4
Totallean (%) 47.1 52.8 52.4 59.5 52.5
External fat (% ) 12.5 10.8 9.7 5.4 11.0
Total fat (% ) 35.4 28.7 27.7 17.6 30~5
Carcass grade c 12.6 11.6 9.1 8.7 10.6
a Adapted from Wanderstock and Miller (1948).
b treatments: Lot 1, full-fed in drylot; Lot 2, full-fed ground corn on pasture; Lot 3, grazed on
pasture for short time, then full-fed in drylot; Lot 4, grazed on pasture only; Lot 5, grazed on
pasture full season, then full-fed in drylot.
c 13 = average Choice; 10 = average Good; 7 = average Standard
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104 MARCHELLO AND HALE
Jacobson and Fenton (1956) observed the effects of three feeding
levels and animal age (30-80 weeks) on the quality of beef from
Holstein cattle. The three levels of nutrition represented 60%, 100%,
and 160% of the amounts of total digestible nutrients according to the
upper limits of Morrison's (1949) standards for growing dairy heifers.
Small differences in the amounts of intramuscular fat were noted as
the nutrition level increased (Table 41. About 3% of intramuscular
fat for the cattle receiving the high level of nutrition approaches the
lower limit of what is observed in a beef carcass graded Choice by
today7s standards.
The data in Table 4 strongly suggest that the levels of nutrition had
no effect on the palatability of the meat coming from these cattle.
Animal age had a much greater effect on palatability than nutritional
level. Ages considered were 32, 48, 64, and 80 weeks. Animals 32-48
weeks of age at slaughter had similar levels of intramuscular fat ( 1 .2~o );
older cattle had twice as much.
In general, Jacobson and Fenton (1956) concluded that the fat
content and shear values increased with animal age. Scores for aroma,
flavor, juiciness, and tenderness decreased after 48 weeks of age, re-
gardless of nutritional regime.
Guenther et al. (1965) used half-sib Hereford steer calves (225 kg)
to determine the effect of plane of nutrition on growth and development
from weaning to slaughter weight. The design permitted comparison on
both an age- and weight-constant basis. The design of the experiment
was as follows:
Lot W Calves were slaughtered at weaning time.
Lot HI Calves were fed on a high plane of nutrition to 125 kg post-
weaning gain, then removed from test and slaughtered.
TABLE 4 Levels of Nutrition for Beef Cattle: Their Effect on Fat
Content of Muscle and Palatability ~
Palatability Evaluation
Level of Fat
Nutrition ~( % ) Aroma c Flavor c Juiciness c Shear Value d
Low 0.8 6.8 6.7 7.0 6.4
Medium 1.8 6.6 7.3 7.5 7.7
High 2.7 6.7 7.3 7.3 6.4
a Adapted from Jacobson and Fenton (1956).
b Low, medium, and high represent, respectively, 60%, 100%, and 160% of the amounts of total
digestible nutrients recommended by Morrison (1949).
c Ten-point scale with 10 being most acceptable.
Kilograms of force to shear a core 2.5 cm in diameter. The higher value is less tender.
OCR for page 105
Nutrition and Management Aspects of Ruminant Animals 105
Lot Ma- Calves were fed on a moderate plane of nutrition. They
were removed from test and slaughtered at the same time as the H.
calves (age-constant basis) .
Lot H2-Calves were fed on a high plane to 205 kg postweaning gain,
then slaughtered.
Lot M2 Calves were fed on a moderate plane. They were removed
from test and slaughtered at an age-constant basis to the H2 calves.
Lot Ma-Calves were fed on a moderate plane to 205 kg postweaning
gain. They were slaughtered on a weight-constant basis with the He
calves.
Feed requirements per unit of gain were largest during the initial
phase of the feedlot period and greatly favored the high-level steers over
the age-constant moderate group of steers. On a weight-constant basis,
however, little difference was noted in feed requirements. Carcass grade
also favored the high-level cattle.
Fat accumulation was most rapid during the latter half of the feed-
ing period and showed a sharp increase after lean production began to
subside. Thus the lean: fat ratio became smaller and less desirable as
the feedlot period was extended past this point. Experimental steers
weighed about 355 kg and were almost 11 months old at this time. Com-
parisons of the influence of nutritional treatment on fat content of
certain carcass wholesale cuts are made in Figure 1. Sizable differences
were noted for some of these cuts. Fat-deposition trends were estab-
lished for each wholesale cut although considerable variation existed
between cuts.
Lofgreen (1968) determined the body composition of cattle follow-
ing the application of varying planes of nutrition in both feeder calves
and yearling steers.
The following design was used:
~t Low-energy ration (20% concentrate) for 273 days.
LEH Low energy for 182 days and high energy (90% concentrate)
for 91 days.
EMH Low energy for 91 days, medium energy (55% concentrate)
for 91 days, and high energy for 91 days.
HML High energy for 91 days, medium energy for 91 days, and low
energy for 91 days.
HHL High energy for 182 days and low energy for 91 days.
HHH High energy for 273 days.
The results of this experiment are given in Table 5. Increasing the
level of concentrate resulted in carcasses that carried greater amounts
OCR for page 106
l o -
7.5
ySO #:
O ~ 1 .
W H'M'H2M2M3
106 MARCHELLO AND HALE
CHUCK RIB LOIN ROUND
W H. Ml H2M2M3 W H. M, H2M2M3
TREATMENTS
W H' M'H2M2M3
FIGURE 1 Effect of plane of nutrition on deposition of fat in certain wholesale
cuts of beef. Treatments: W. slaughtered at weaning time; H1, high plane for
125 kg of gain; M1, moderate plane and slaughtered at the same time as H1; H.,
high plane for 205 kg of gain; M-, moderate plane and slaughtered at same time
as He; Me, moderate plane for 205 kg of gain. (Adapted from Guenther et Cal.,
1965)
of body fat. This effect was more pronounced in yearling cattle than
in calves. Differences in marbling score (intramuscular fat) were small
and apparently not influenced to a large degree by nutrition in either
age group. Marbling values observed would have permitted most of
the carcasses to be considered for the Choice grade as determined by
current federal grading standards. Therefore, meat cuts from these
cattle could be presumed to have high consumer acceptability, regard-
less of nutritional regime.
However, Zinn et al. (1970) found marbling scores and carcass
grades to increase significantly (p<0.05) up to 240 days on feed.
Steers reached a given grade 30-60 days earlier than heifers, even
though deposition of intramuscular fat was similar between sexes. The
data indicated that steers and heifers deposited intramuscular fat at a
similar rate and that deposition of intramuscular fat is not a continuous
process but proceeds in stages at intervals of 60-90 days.
The effect of nutritional level imposed from birth to 8 months of age
on subsequent development of full-fed beef calves was investigated by
Stuedemann et al. (19681. Each of five groups of calves was subjected
to one of the following nutritional levels: very restricted, restricted,
OCR for page 107
Nutrition and Management Aspects of Ruminant Animals 107
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108
MARCHELLO AND HALE
normal, high, and very high. These levels were based on milk pro-
duction of the dam and additional supplementation. In those calves
slaughtered at 8 months of age, the relative amounts of lean, fat, and
bone tissue produced were directly influenced by the level of nutrition
imposed. As the level of nutrition decreased, significantly (p<0.05),
less tissue was produced. The relative retardation of growth was greatest
in fat tissue, followed by lean and bone (Figure 21.
Differences in the average daily feedlot gains of the calves were not
statistically significant. However, calves subjected to the lower planes
of nutrition during early life required more days in the feedlot to attain
the desired constant market weight. Regardless of nutrition in early life,
once the cattle completed the feedlot period at a constant weight, no
differences were noted in carcass composition (Figure 21.
Results in contrast with these were obtained by Winchester et al.
(1967), who conducted a study in which identical twins were used.
One member of the pair was restricted in plane of nutrition for periods
of 3-6 months; the other was allowed to grow and develop on a normal
plane of nutrition. Little difference was observed in the final carcass
composition of these calves when they were slaughtered at equal body
weights.
CHUCK Rl B LOIN ~ ROUND
1 2 3 4 5
1
I.
1 2 3 4 5 1 2 3 4 5
MARKET
WT.
8 MO
WT.
1 2 3 4 5
TREATMENTS
FIGURE 2 Effect of nutritional level imposed from birth to 8 months of age on
the amount of fat in the round, rib, loin, and chuck of beef calves slaughtered at
8 months and at a constant market weight. Treatments: 1=very restricted, 2=re-
stricted, 3=normal, 4=high, 5=very high. (Adapted from Stuedemann et al.,
1968 )
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Nutrition and Management Aspects of Ruminant Animals 109
A similar situation appears to be true for sheep, as revealed by
Burton and Reid (19691. Regression coefficients between body com-
ponents and body weight are given in Table 6. The composition of the
carcasses was not influenced by plane of nutrition when the sheep were
evaluated at equal body weights.
Berg and Butterfield (1968) reviewed the growth pattern of bovine
muscle, fat, and bone and concluded that a high plane of nutrition in-
creases the percentage of carcass fat. This conclusion was based on the
results presented by Guenther et al. ( 1965), where the differences
were not statistically significant. Consequently, Preston (1971) stated
that the evidence for such an effect is meager arid that, in fact, there is
overwhelming evidence that plane of nutrition has little or no effect
on final carcass composition in cattle and sheep at constant weights.
Utley et al. (1971) conducted a 3-year study of two systems for
finishing beef steers. The purpose was to evaluate the influence of the
systems on feedlot performance and carcass merit. One system was
designed to make maximum use of harvested and grazed forages; the
other was designed to maximize gains by feeding a high-energy finishing
diet from weaning time (219 kg) to a slaughter weight of 455 kg. The
steers fed the high-energy diet reached market weight, on the average,
153 days sooner than the steers on the roughage system. Dressing per-
centages and subcutaneous fat thickness were slightly lower for the
forage-fed cattle, but carcass grades were similar for both groups.
However, Garrett (1974) found in comparing yearling steers fed
20%, 40%, or 60% alfalfa in the finishing diet that the carcass grades
were similar but that the 40% and 60% alfalfa groups had carcasses
with about 4% less body fat than the 20% alfalfa group (Table 71.
Grain consumption by the steers ore the 60% alfalfa diet was 28%
less than those on the 20% alfalfa diet, and steers in the former group
required an additional 40 days to reach comparable finishing weights.
These results suggest that management systems can be developed that
TABLE 6 Regression Coefficients between Body Components (kg)
and Empty-Body Weight (kg) of Sheep Receiving Two Energy Levels a
Energy
Level Water
Body Components
Fat Protein Ash
Energy
High 0.357 0.517 0.109 0.018 5.517
Low 0.376 0.498 0.106 0.019 5.344
a SOURCE: Burton and Reid (1969). Courtesy, Journal of Nutrition.
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Representative terms from entire chapter:
body composition
110
MARCHELLO AND HALE
TABLE 7 Response of Heavy Steer Calves Fed Three Levels of
Alfalfa a
Level of Alfalfa in the Ration
Variable 20% 40% 60%
Final weight (kg)b 474 486 495
Total gain (kg) 184 195 203
Days on feed 140 161 182
Average daily gain (kg)h 1.3 e 1.2e, f 1.1
Grain in the diet (% ) 71.2 53.3 35.3
Total "rain consumed (kg) 848 803 607
Total carcass fat (% ) 34.0 c 30 3 f 30.1 t
Carcass grade c 10.3 10.8 1 1.0
Yield grade ~2.9 3.0 2.8
SOURCE: Garrett (1974) .
7> Correct to dressing percentage of 62.
c Carcass grade: 9 = low Good; 10 = average Good; 11-high Good.
The lower scores have higher curability percentages.
e,t Values on the same line with unlike superscripts differ (p < 0.05).
utilize less grain with acceptable feedlot performance, yet produce
desirable carcasses with less fat.
Hormonal growth stimulants have been effectively used in the live-
stock industry for many years to increase weight gains. Marchello et al.
(1970) evaluated the influence of some of them on fat deposition in
conjunction with seasonal effects (Table 81. None of the stimulants
compared were effective in reducing the deposition of subcutaneous or
intramuscular fat. However, some of them improved the curability
of the carcass, which is surprising since curability is largely dependent
on the amount of subcutaneous fat present. Possibly this can be at-
tributed to a greater proliferation of muscle growth.
The cattle finished in the summer months significantly (p
Nutrition and Management Aspects of Ruminant Animals 111
TABLE 8 Influence of Season and Hormonal Growth Stimulants on
Certain Traits of Beef Carcasses a
Fat Intramuscular
Thickness Fat Cutability
(cm) (%) (%)
Summer
Control 1.7 19.1 49.0
MGA 1.6 19.4 49.1
Winter
Control 1.2 16.5 50.2 b, c
MGA 1.3 16.2 49.9 b
DES 1.1 17.0 50.7 c
Summer
Control 1.9 15.9 48.2 ~
MGA 1.8 16.2 48.3 b
Synovex-H 1.7 15.6 49.0 b, c
Rapigain-1 1.6 15.0 49.6 c
Winter
Control 1.0 15.5 50.5
MGA 1.0 14.5 50.5
Synovex-H 1.0 15.6 51.0
Rapigain-1 1.0 15.8 50.8
a Adapted from Marchello et al. (1970).
b,c Values for each season with unlike superscripts differ significantly (p < 0.05).
TABLE 9 Effect of Synovex and Ralgro on Body Composition of
Beef Cattle a
Body Composition c
Slaughter
Weight Quality Yield Fat Protein
Treatment (lb) Grade b Grade (% ) (% )
Control 1047 1 2.S 2.4 32.4 d 15.0 d
Synovex 5 initially
No additional 1074 11.9 2.3 29.5 e 15.66
Synovex reimplant 1156 12.3 2.3 29.06 15.7 e
Ralgro reimplant 1123 12.2 2.2 29.5 c 15.6 e
Ralgro initially
No additional 1091 11.8 2.1 29.se l5.6e
Synovex reimplant 1096 11.9 2.4 29.se l5.6e
Ralgro reimplant 1078 12.1 2.1 3o.o e 15.5 e
Synovex S+Ralgro 1105 12.3 2.3 29.0 e 15.7 e
a SOURCE: Lofgreen (1974).
h 13 = average Choice; 12 = low Choice; 11-high Good.
c Determined by specific gravity.
die Values within the same column with unlike superscripts differ significantly (p < 0.01).
i12
MARCHELLO AND HALE
different from those presented by alteration of the fat content of fed
steers. Differences in the fat content of milk from cows fed typical
diets are reflections of the genetics of the animals. A producer is paid
for his milk on the basis of fat content, and regulations in most states
fix, or at least limit, the lower level of fat in retail whole milk. Thus,
any feeding or management system whose purpose is to change the fat
content of milk may be undesirable. The chances that a change would
be undesirable are increased if the purpose is to lower the fat content.
Any desired change in the fat content of retail milk can easily be made
by the processor.
Fat percentages in milk may be depressed by certain feeding sys-
tems for example, feeding finely ground feeds, feeding highly digestible
roughages, and high levels of grain feeding (Davis and Brown, 19701.
In practice, fat levels in milk are sometimes inadvertently depressed by
some change in feeding management, and immediate efforts are made
to restore the fat level to normal. The effect of reduction of fat levels
in milk due to feeding systems on total milk production over the entire
lactation is unknown.
In the last 30 years, there has been a marked increase in milk yield
per cow. In part, this increase is due to genetic improvement, man-
agement, and disease control. The greatest increase is probably due to
improved nutrition for the cows. There has been an improvement in the
metabolizable energy (ME) of forages, resulting from improvement in
harvesting methods, and an increase in the ME intake of the lactating
cow as a result of grain feeding.
It is possible to meet the energy requirements of cows producing
20 kg or less of milk per day by feeding only good-quality alfalfa hay;
however, efficiency of production would be improved by including some
concentrate in the feeding system. For cows with the ability to produce
30 kg or more of milk per day, concentrate feeding is essential, because
roughage or corn silage diets do not contain sufficient ME to meet the
energy requirements of the cows.
S UM MARY
Alteration of carcass composition of ruminants through nutrition ap-
pears possible. However, when the available literature was surveyed,
it was apparent that compositional changes are difficult to accomplish
without resorting to drastic reduction in energy intake for prolonged
periods. Within the practical realm of rations fed to cattle and sheep,
plane of nutrition will not alter the gross chemical composition of their
carcasses. This is not to say that changes do not occur histologically
or in the distribution of carcass constituents.
Nutrition and Management Aspects of Ruminant Animals 113
In comparing usual nutritional regimes, it is apparent that if the ani-
mals are fed to constant final slaughter weight, major differences in
carcass composition are eliminated. However, if the ruminants are sub-
jected to a prolonged negative energy balance, a carcass is produced with
increased fat content if the animals are provided with a marked positive
energy balance before slaughter weight is attained.
Reduced planes of nutrition that result in compensatory growth when
cattle are placed on full feed yield animals with altered body composition
for a period of time. However, these animals have carcasses similar in
composition to those of full-fed animals once slaughter weight is
reached. Apparently, the growth phase of these animals is prolonged
until certain body needs are met, then fat accumulation predominates.
Animal age plays an important role in body composition. At very
young ages, body composition will be predominantly water and protein.
As the animals advance in age, fat content will increase at an increasing
rate regardless of nutritional regime provided the animals are in positive
energy balance. It seems reasonable to assume that reduced nutrition
at very young ages would result in altered composition at slaughter
weight. However, if a high plane of nutrition is provided as part of the
feeding regime, differences in carcass composition are minimal.
The season of the year may influence the deposition of fat. This
appears to be mediated as a body defense mechanism to cope with ad-
verse environmental conditions. High environmental temperatures pro-
mote the deposition of large quantities of fat. It is also conceivable
that high temperatures would alter fat composition.
With the possibility of an indefinite shortage of feed grains, feeding
systems must be evaluated with the aim of preserving quality while
using less grain. It is conceivable that these systems can be used without
sacrificing consumer acceptance of the meat cuts. The data presented
in this chapter show that lowering grain levels in finishing diets merely
results in lower daily gains with no effect on carcass composition. Ex-
periments must be designed to specifically evaluate the effects of reduced
grain feeding on economy, production, carcass composition, and palat-
ability.
Adoption of management systems that use less grain could necessi-
tate significant changes in the federal carcass-grading standards. Further-
more, for snaky years, packer buyers have selected cattle and sheep for
purchase primarily on the basis of grade and dressing percentage. The
use of dressing percentage poses a problem, because it promotes the
propagation of animals possessing unwanted quantities of waste fat.
Alternative procedures must be considered. The United States is
probably the only country using an outdated system for marketing ani-
mals. The use of a procedure that would reflect the merits of the carcass
114
MARCHELLO AND HALE
seems much more desirable. The adoption of mandatory yield-grading
would help alleviate this problem. However, until producers and feeders
are compensated for producing cattle and sheep with superior carcasses
(more high-quality lean and less fat), the marketing system will con-
tinue to price slaughter animals on the same level, regardless of merit.
Nutritional and management systems that can alter the fat content
of milk are available. However, because of the present pricing system,
which is based on fat, it is inadvisable to consider any of these systems;
they would result in direct monetary losses to the production unit.
Furthermore, fat level in retail milk can be adjusted easily at the
processing stage. An alternative system using solids-not-fat as a base
seems more realistic.
It is not within the scope of this chapter to consider the genetic consti
tution of ruminants. The propagation of superior animals with superior
genotypes with regard to carcass composition appears to be the most
logical procedure to attain the desired end product. This, coupled with
proper nutritional regimes, could result in the production of cattle and
sheep that provide carcasses that are relatively free of waste fat and
possess meat quality that has optimum consumer acceptance.
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