CHLORTETRACYCLINE AND PROTEIN LEVEL IN RATIONS FOR MARKET HOGS: I. EFFECT ON RATE OF GAIN AND EFFICIENCY OF FEED UTILIZATION

A study was made of the effect of protein level and chlortetracycline (aureomycin) supplementation on rate of gain and feed efficiency of market hogs, self-fed from weaning to market weight. Four different levels of protein (i.e., approximately 13, 15, 17 and 19 per cent from weaning to 70 lb.; approximately 12, 13.5, 14.5 and 15.5 per cent from 70 to 130 lb.; and approximately 11, 12, 12.5 and 13 per cent from 130 to 200 lb.;) with and without chlortetracycline were used.For the over-all feeding period (i.e. from weaning to market weight) the addition of aureomycin caused statistically significant increases in rate of gain at all protein levels. Protein level also affected rate of gain significantly. The effect of the "Protein × Antibiotic" interaction on rate of gain was found to be significant.Aureomycin improved feed efficiency at all protein levels, significantly so at the low and medium levels. Protein level had no significant effect on feed efficiency for the feeding period as a whole.Aureomycin significantly increased over-all feed consumption at the standard protein level only. Protein level significantly influenced feed consumption. The effect of the "Protein × Antibiotic" interaction on feed consumption was significant.