.C)-pna Agricultural Research Center *
S RC-1972-6 April, 1972
The Use of Methionine Hydroxy Analogu IUME LIBRARY
Beef Cattle Rations
/ 1 M W1972
H. L. Chapman, Jr.. M,.g
Synthetic non-protein-nitrogen compounds, such as ur .W r bQ v 4cFlorida
increasingly in feeds,for beef cattle. It has been long recoughled that
rumen microorganisms can convert this synthetic nitrogen to protein. However,
there have been some indications, particularly with young cattle, that urea
nitrogen.may not be as well-utilized as plant protein nitrogen, particularly
during relatively short feeding periods. During recent years there has been
some suggestion that some amino acids, particularly methionine, may limit protein
synthesis by rumen microorganisms but research results have varied concerning
the value of adding supplemental amino acids to beef cattle rations. These
studies were to determine if methionine hydroxy analog (MHA) would stimulate
the growth of calves on pasture, or of steers fed in drylot, in south Florida.
Three experiments were conducted,two with weanling calves on pasture and
one with two-year-old steers being fattened in drylot. During the first study
48 weanling heifer calves were divided into four equal groups on the basis of
weight and breed and the groups randomly allotted to experimental treatment.
A complete concentrate mixture comprised of dried'citrus pulp, corn meal, cane
molasses, 17% dehydrated alfalfa meal, a mineral mixture and supplemental nitrogen
was fed. The feed mixture had 14% crude protein. Supplemental nitrogen was
finished by urea or cottonseed meal, each with and without 3 grams per head
daily of MHA. Each experimental group grazed 10 acres of mixed pasture and
received 1.5% of their body weight in concentrate for 166 days.
The second study was with 55 bull calves, divided into two groups on the
basis of breed and weight and fed for 166 days on unimproved pasture. The
protein supplements compared were cottonseed meal and urea plus 3 grams of MHA
1/ Animal Nutritionist and Director, Agricultural Research Center, Ona, Florida.
2/ W. G. Kirk. 1972. Unpublished data.
per animal, daily. 'Each group had 40 acres of unimproved pasture. The
experimental rations were the same as for the heifer calves. Since the bull
calves were on native range they were fed pangolagrass hay free.choice in
addition to lk% of their body weight in concentrate feed.
The third study involved 36 Brahman x Shorthorn.x Charolais steers being
fattened in the drylot. The experimental ration consisted.of 1600 lb. dried
citrus pulp, 1600 lb. cornmeal, 100 lb. 17% dehydrated alfalfa.pellets, 300 lb, *
cane molasses, 400 lb. bagasse pellets, 80 lb. Cyrea and 20.1b. mineral mixture.
The steers were divided into four groups of nine animals each, on the basis of
weight. Two groups received the above ration and two groups received the ration
plus 3 grams MHA per steer daily. The ration was full-fed in drylot for 134 days.
The results of the growth studies are shown in Tables 1 and 2. The effect
on gain was variable. MHA did not increase the rate of gain of the heifers
(Table 1). Calves receiving urea grew as well'as those fed cottonseed meal.
The bulls receiving urea.plus MHA had approximately 6% more gain than those
receiving cottonseed meal.'
In the fattening study (Table 3) when the groups receiving urea were
averaged together and thetwo groups, receiving urea plus MHA were averaged,
the former had about 4% more gain than the groups fed MHA. At the end of 70
days the steers fed MHA had gained about 47. faster, but this benefit did not
last for the entire feeding period.
Table 1. Average gain of heifer calves fed different protein supplements
on pasture (length of test, 166 days).
CSM MKA Urea MHA
Number of calves 12 12 12 12
Initial weight, lb. 482 479 484 484
Final weight, lb. 720 714 734 719
Total gain, lb. 238 235 250 235
Daily gain, lb. 1.43 1.42 1.51 1.42
Table 2. Average gain of steer calves fed different protein supplements
on pasture (length of test, 166 days).
Number of calves 26 28
Initial weight, lb. 567 563
Final weight, lb. 777 761
Total gain, lb. 210 198
Daily gain, lb. 1.27 1.19
1/ One calf died, cause unknown.
Table 3. Average gain of steers fed different protein supplements in drylot
(length of test, 134 days).
Urea MHA Urea MIA
Number of steers 9 9 9 9
Initial weight, lb. 816 816 814 816
Final weight, lb. 1131 1133 1132 1107
Total gain, lb. 315 317 318 291
Daily gain, lb. 2.35 2.37 2.37 2.17