Purdue University
Agricultural Experiment Station
Lafayette, Indiana
Mimeo A.H. 164 April 27, 1956 (Progress Report)
DIFFERENT LEVELS OF AUREOMYCIN IN A FATTENING RATION
D0 L. Jeter, Te W. Perry and W. Mo Beeson Department of Animal Husbandry
Feeding antibiotics to suckling calves has been shown to be beneficial in increasing growth rate and alleviating scours. With the discovery of this fact, work was then initiated to test the effect of antibiotics when fed to older animals in which rumen function was more developed.
Early work along this line indicated that antibiotics had a depressing effect on growth rate or no effect at all, but later work has shown that this result was due to the fact that either too high levels of antibiotics were being fed or that the feeding of the antibiotics was for too short a period of time. Work at Purdue (A.H. Mimeos 120, 130, 142) and at other stations has more recently shown that antibiotics, such as aureomycin or terramycin, have increased feed efficiency and rate of gain when fed to cattle on high roughage rations or when a limited amount of corn is fed.
The generally recommended level of feeding antibiotics on this type of ration is 10 milligrams of antibiotic per one hundred pounds of liveweight daily, or, if it is to be fed to yearling cattle, a level of 75 to 80 milligrams per head per day over the entire fattening period is effective. On high corn or low roughage diets, supplementation with antibiotics at this level has not given consistent improvements in rate of gain or feed efficiency.
This experiment was designed to determine the most effective level of feeding aureomycin in a high corn diet.
Experimental
Seventeen yearling Shorthorn steers and heifers from the experimental Shorthorn herd and seven yearling Hereford steers, that were raised in New Mexico, were divided into four lots on the basis of weight and sex, and so that the Herefords were as evenly distributed as possible. All lots were fed a basal ration of mixed hay free choice, a full-feed of ground ear corn (approximately 2 pounds of corn per 100 pounds of liveweight per day;, 2 pounds of Purdue Supplement A per head daily, and a simple mineral mix and salt free choice. The cattle were hand-fed twice daily, and the supplement was mixed in with the ground ear corn by hand at the time of feeding.
Treatments are as follows:
Lot 1	-	Control (basal ration only)
Lot 2	-	Basal	ration	plus	25 nig. of	aureomycin/head	daily
Lot 3	-	Basal	ration	plus	75 mg. of	aureomycin/head	daily
Lot 4	-	Basal	ration	plus	125 mg. of aureomycin/head daily
Aureomycin was supplied by Aurofac 2A which contains 3•6 gm. aureomycin per pound. This was incorporated in Supplement A so that two pounds °T Supplement A supplied the levels indicated above.