Growth and Carcass Characteristics of Pigs Fed Antibiotics for Part or all of the Growing-Fattening Period

Abstract

One hundred and fifty-two weanling pigs were fed in two experiments to compare the value of aureomycin, terramycin and procaine penicillin when fed for part or all of the feeding period, and to determine the need for vitamin B12 supplementation of a ration which contained dry-rendered tankage. The addition of vitamin B12 to the basal ration produced a highly significant (P less than .01) increase in rate of gain, even though the supplement fed contained 20 percent of high quality, dry-rendered tankage. The addition of aureomycin produced a further increase that was highly significant. The addition of terramycin or procaine penicillin increased gains significantly (P less than .05) The withdrawal of the antibiotics when the pigs weighed an average (lot weight) of 125 pounds had a pronounced depressing effect on daily feed consumption and rate of gain in the first experiment. In the second experiment there was no adverse effect on feed consumption, but withdrawal of aureomycin or terramycin had a slight depressing effect on rate of gain. The feeding of added vitamin B12 or of any of the antibiotics did not affect feed efficiency of the pigs significantly. The percent of moisture, crude protein or fat in the carcasses was not affected significantly by the feeding of any of the antibiotics or of vitamin B12.The percent of ash in the carcasses was decreased significantly in all but one of the lots of pigs fed antibiotics. It is concluded that when environmental conditions are such that an antibiotic will have a significant effect on the growth rate of the newly weaned pig, the antibiotic should be fed from weaning to market weight, if maximum gains are desired. It is concluded also that aureomycin, terramycin or procaine penicillin per se do not directly affect carcass quality.