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L I E> R.AR.Y

OF THL

UNIVERSITY
OF ILLINOIS



G30.7



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MRICULTURE



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PREGNANCY



QUALITY OF BEEF



By R. R. Snapp and Sleeter Bull



Bulletin 508

UNIVERSITY OF ILLINOIS
AGRICULTURAL EXPERIMENT STATION



CONTENTS

INTRODUCTION 431

PLAN OF THE EXPERIMENT 432


DISCUSSION OF RESULTS 434

Live Animals 434

Carcasses 439

SUMMARY 451

CONCLUSIONS . .452



Urbana, Illinois December, 1944

Publications in the Bulletin series report the results of investigations made
or sponsored by the Experiment Station



EFFECT OF PREGNANCY ON
QUALITY OF BEEF

By R. R. SNAPP, Chief in Beef Cattle Husbandry, 1 and
SLEETER BULL, Chief in Meats

IN THE LIVESTOCK and meat industry the effect of sex on the
quality of beef has always been a subject of considerable contro-
versy. On the livestock market heifers usually sell for two or three
cents a pound less than steers of equal grade, and heifer beef usually
sells for less in the wholesale house than steer beef. There is, however,
no price distinction in the retail market. Altho sex differences are not
discernible in retail cuts, most consumers believe that heifer beef is
inferior to steer beef and will not knowingly buy it except at a cut
price. For this reason the retailer usually sells heifer beef as steer
beef and at the same price.

The Illinois Station made a comparison of the beef from steers and
open heifers in 1926-27, from which the following conclusions were
drawn : 2

. . . the much vaunted superiorities of the steer over the non-pregnant
heifer as a butcher's beast are not so great as has been claimed by many in
the beef trade. As a matter of fact, light heifers (weighing around 700
pounds after 140 days of feeding) proved to have distinct advantage over
steers of similar feeding, breeding and weight in the matter of finish and
they cut out almost as well. There would seem to be no logical reason for
a price discrimination against the light heifer on account of her sex.

Heavier heifers (weighing 800 to 900 pounds after 200 days of feeding)
are slightly inferior to steers of equal weight, being a little over-done. The
heavy steer cuts out to slightly better advantage than the heavy heifer,
owing to the excessive condition which is oftentimes found in the heifer,
but the superiority of the heavy steer is not sufficient to justify the usual
price discrimination of 1 to 3 cents a pound in favor of the steer carcass.
If the producer will market heifers after a shorter feeding period and at
lighter weights than steers of equal age and quality, it will be to his
financial advantage.

There were no differences in dressing percentages between steers and
heifers slaughtered in feeder condition nor when slaughtered after 140 days
of feeding. There is an indication that the heifers dressed a little better
than the steers when fed for 200 days. . . .

As slaughter cattle the heifers graded about the same as the steers.
When both were fed 140 days, the heifer carcasses, however, graded some-
what higher than the steer carcasses. When fed for 200 days, the slaughter

] On leave for military service.

"Effects of sex, length of feeding period, and a ration of ear-corn silage on the quality
of baby beef. 111. Agr. Exp. Sta. Bui. 355. 1930.

431



432 .BULLETIN No. 508 {December,

steers graded slightly higher than the heifers. The carcass grades were
about the same; however, considering the usual discrimination against any
except light heifers, it is probable that the carcasses of the heifers fed for
140 days would have sold better than those of the heifers fed for 200 days.
The palatability committee did not detect any particular differences in
the palatability of the roasted beef that could be attributed to sex.

Since many heifers are bred before they are marketed, an experi-
ment was conducted in 1930-31 to study the effect of pregnancy on the
quality of beef. That pregnancy has an important effect on the feeding
and killing qualities of cows and heifers is commonly believed by
feeders and butchers. Many farmers have an aversion toward heifers
for feeding purposes, because they believe that the frequent heat
periods (every three weeks) give rise to considerable disturbance
among feedlot cattle, which is detrimental to good gains. It is largely
to lessen such disturbances that the breeding of heifers soon after they
are started on feed is a rather common practice. Feeders are inclined
also to believe that the gains are increased by the presence of the
young in utero ; consequently they favor the breeding of cows and
heifers which are being fattened for market on the theory that preg-
nancy induces more rapid and economical gains.

On the other hand, buyers and butchers object to heifers largely
on the grounds that many of the heifers marketed are pregnant and
hence have a relatively low dressing percentage. Sometimes the claim
is made that heifers slaughtered while pregnant do not bleed out well
and consequently produce dark-cutting carcasses. Thus buyers con-
sider that they have good reasons for making severe price discrimina-
tions against female cattle that are old enough to be several months
along in gestation. Feeders, on the other hand, believing that their cows
and yearling heifers will be bought on a pregnancy basis, feel fully
justified in marketing them in a pregnant condition. Thus a circle of
cause and effect exists, futile in nature if the alleged benefit of larger
and cheaper gains credited to pregnancy is largely offset by decreased
dressing percentage, lower quality of carcass, and lower selling price.



PLAN OF THE EXPERIMENT

For the experiment 10 Hereford heifers were selected from a car-
load of choice yearlings bought in the fall of 1930 in northern Texas:
Their exact age was unknown, but their weight and general appearance
indicated that they were about 16 or 18 months old when purchased.



1944~\ EFFECT OF PREGNANCY ON QUALITY OF BEEF 433

The paired feeding method, a method first described by Armsby 1
in 1917, was used. The animals were compared by pairs, each pair
consisting of one open and one bred heifer as nearly alike as possible
in age, type, weight, condition, and other items which presumably
affect their feeding and killing qualities. The animals were started
on feed November 7.

The original plan of the experiment was -to feed each pair of heifers
a maintenance ration of about 4 pounds of shelled corn and 6 pounds
of clover hay per head until one of the pair was observed to be in heat,
whereupon this heifer was to be bred. Then she and her paired mate
were to be fed a fattening ration for 150 days. At the end of this period
both animals were to be slaughtered. Since none of the heifers, how-
ever, had shown any signs of estrum after two weeks on the low level
of feeding, the ration was increased to a full feed of grain and one
pound of linseed meal per head daily. Apparently the improved ration
was effective, for at least one heifer of each pair came in heat during
the next thirty days. The dates when the heifers conceived (Table 1)
are considered the beginning of the experiment for each pair.

All the heifers, haltered and tied to separate mangers for two hours
each morning and evening, were fed individually. Both heifers of each
pair were fed identical rations, the amount of feed being determined
by the animal with the smallest appetite. Since some of the heifers
would not eat all their hay, it was replaced in all rations on December
19 by about 10 pounds of corn silage. Except at feeding time the heifers
were allowed to run loose in their sheds, which adjoined open lots. As
soon as five heifers were bred, the bred and open heifers were kept in
different lots in order that observations might be made of the relative
activity of the two groups. At 28-day intervals each animal was
weighed and ten body measurements were taken.

One hundred and fifty days after the breeding of a heifer she and
her paired mate were slaughtered (Fig. 1). This period of time was
chosen because yearling heifers are seldom fed longer than six months
for the open market. If it takes three or four weeks of rather liberal
rations in the feedlot before thin range-bred heifers show signs of heat,
as was true in this experiment, few heifers that are open when put into
the feedlot will be more than five months in calf when sold for
slaughter. Consequently, the effects of gestation observed in this experi-
ment may be regarded as the maximum effects to be expected in year-
ling heifers bred after being placed in the feedlot. The effects of

'Cooperative experiments upon the protein requirements for the growth of
calves. Bui. Natl. Res. Council 12, 219-288. 1921.



434 BULLETIN No. 508 [December,

gestation after 150 days would, of course, be more marked in heifers
that were well advanced in pregnancy when started on feed.

All data were analyzed statistically by Student's method for the
interpretation of paired experimental data. When the value of "P" was
greater than .05, the results were regarded as insignificant.



DISCUSSION OF RESULTS
Live Animals

Activity. The pregnant heifers showed a little more tendency to
lie down than did the open heifers, and when lying down they were
less inclined to rise when being approached. These differences, how-
ever, were not statistically important. Of more importance were the
differences in temperament. The pregnant heifers were more easily
caught and tied than were the open heifers and appeared to be more
content. The more quiet disposition of the pregnant heifers was ap-
parent each month when body measurements were being taken. It was
comparatively easy to measure the pregnant heifers, but the open
heifers resented being handled and frequently became nervous and
excited.

Close observations were made of the five open heifers to determine
the extent to which they were disturbed by one of them being in heat.
Signs of heat were not easily detected, however, particularly during
the last half of the feeding period. Only on three occasions was a heifer
in heat ridden repeatedly by other heifers in the lot. 1

Appetite. The amount of feed consumed could not be taken as a
measure of appetite, since the bred and the open heifers 'were given
the same amounts of feed. Accordingly observations were made to de-
termine how rapidly and completely each animal consumed its feed.

The pregnant heifers possessed keener appetites than their open
mates, as was evident from both the speed and completeness with which
they ate their feed. At practically all stages of the test the bred heifers
would have eaten somewhat more feed if it had been given to them. 2

Rate of gain. Altho all heifers made fairly g-ood gains, the gains
of the pregnant heifers were not significantly larger than those of
the open animals (Table 1). Apparently the (continued on page 439)

'In experiments at the California Station it was concluded that "activity of
open heifers in riding each other at estrual periods is not serious." Cal. Agr.
Exp. Sta. Bui. 645. 1940.

"These results do not agree with those of the California Station (Bui. 645),
from which it was concluded that "pregnancy in cattle does not cause increased
appetite."




Fig. 1. Heifers at the time of slaughter. The bred heifers (B) are shown
at the left; their open mates (O), at the right.



436



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increase in the weight of the bred heifers due to the developing fetus
was largely balanced by slower body growth. These results agree
closely with the findings of other investigators who kept open and bred
heifers on the same level of feeding during the first half of the gesta-
tion period. 1 Had the bred heifers been fed to the limit of their appe-
tites instead of being limited to the amounts of feed consumed by their
unbred mates, it is likely that the bred heifers would have shown
larger gains. 2

Growth. The growth made by each animal during the test was
determined by 10 body measurements taken at 4- week intervals. The
parts of the body measured were those believed most likely to be
affected by the devoloping fetus. Pregnancy had little effect on most
of the body measurements taken, but it did have a marked effect on
some (Table 2). If height at withers be taken as the best single mea-
sure of growth, pregnancy retarded growth approximately 11 percent
during the first five months.

The measurements most noticeably affected by pregnancy were
width of loin and width of hip. Thru the loins the bred heifers grew
only 72 percent as much as their open mates, and thru the hips, only
62 percent as much.

Carcasses

Slaughter data. Pregnancy had a significant effect upon the
weights of the liver, uterus and contents, stomach, thymus, spleen, and
shanks (Table 1). The livers of the bred heifers were 6 percent heavier
than those of the open heifers. This difference, altho small, is signifi-
cant (odds 41 to 1). As would be expected, the uteri and contents were
much larger in the bred heifers, averaging 30.2 pounds per 1,000 of
empty live weight 3 compared with 1.6 pounds per 1,000 in the open
heifers.

The percentages of spleen, stomach, and shanks (expressed in per-
centage of empty live weight) in the pregnant heifers were significantly
less (10 to 20 percent) than in the open heifers. In view of other results
of this experiment (see above) it seems logical to conclude that the
lighter weights of these organs were due to the general retarding
effect which pregnancy had on growth. The (continued on page 445)

'Eckles, C. H., and Swett, W. W. Some factors influencing growth of dairy
heifers. Missouri Exp. Sta. Bui. 31, 1918.

"At the California Station (Bui. 645), bred heifers made slightly larger and
more economical gains than open heifers.

"Empty live weight is the live weight just before slaughter minus the weight
of the contents of the digestive tract.




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1944] EFFECT OF PREGNANCY ON QUALITY OF BEEF 445

development of the thymus of the pregnant heifers was less (35 per-
cent) than in the open heifers. If the size of the thymus is, as is gen-
erally believed, an index of potential growth, it appears that pregnancy
hastens maturity.

Dressing percentages. Pregnancy did not affect the dressing per-
centages. Apparently the larger weights of the uteri and contents in the
pregnant heifers (24 pounds on the average at the time of slaughter)
were approximately balanced by the lighter weights of other offal and
the higher condition of the bred heifers. 1

Carcass grade. Two days after a pair was slaughtered, the car-
casses were graded. The carcass grades ranged from Good- to Choice
(Table 1). Altho four carcasses of the bred heifers were assigned
higher grades than those of their open mates, statistical analysis did
not show that the differences were significant. The carcasses of the
bred heifers, however, were without exception more highly finished
than were those of the open heifers. 2

Cutting percentages. One side of each carcass was divided into
ordinary wholesale cuts according to the methods recommended by the
Committee on Cooperative Meat Investigations of the State Agricul-
tural Experiment Stations and the U. S. Department of Agriculture. 3

The loin ends of the open heifers were about 7 percent heavier than
those of the bred heifers (Table 3). Statistically this difference is
highly significant (odds 88 to 1). The rounds also (shanks on, rumps
off) of the open heifers were 11 percent larger than those of the bred
heifers. This difference too is statistically significant (odds 2,500 to 1).
There were no significant differences between the percentages of
other cuts.

Physical composition of carcasses and cuts. The wholesale cuts
were separated with the knife into lean, fat, tendon, and bone, and the
percentage composition of the cuts and of the entire carcass was cal-
culated. Since there was only a small percentage of tendon in any cut,
it is not included in the published tables.

Pregnancy had no greater or more significant effect on any other of
the major items studied in this experiment than on physical compo-
sition of the carcass and cuts (Tables 4 and 5). On the average, the
carcasses of the bred heifers contained approximately 20 percent more

*In the California Station experiments (Bui. 645), pregnancy up to the fifth
or sixth month did not affect dressing percentage.

2 No significant differences in the carcass grades of bred and open heifers
were observed in the California experiments (Bui. 645).

3 A study of the factors which influence the quality and palatability of meat.
Issued for the cooperators by the Anim. Husb. Div., Bur. of Anim. Indus.,
U. S. Dept. of Agr. Mimeo. Rev. ed. Feb., 1927.



446



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1944] EFFECT OF PREGNANCY ON QUALITY OF BEEF 447


1

Online LibraryRoscoe R. (Roscoe Raymond) SnappEffect of pregnancy on quality of beef → online text (page 1 of 2)