Different Protein Levels with and without Antibiotics for Growing-Finishing Swine: Effect on Growth Rate and Feed Efficiency

Abstract

Protein levels of 10, 12, 14, 16, 18 and 20 percent, with and without 5 mg. of aureomycin or terramycin per lb. of ration, were fed in two experiments (numbers 536 and 554) to a total of 288 pigs. The fortified corn-soybean oil meal rations were fed in concrete drylot to pigs weighing from 31 to 36 lbs. to 200 lbs. The level of protein in the ration significantly affected the rate of gain made by the pigs in both experiments as measured by the linear and quadratic components. In general, the average daily gains of the pigs reached a maximum between 16 and 18 percent protein without antibiotics and at 14 percent protein with antibiotics (effect not statistically significant) and then leveled off or declined. Feed efficiency was not significantly affected by the level of protein fed in the first experiment. However, in the second experiment, the protein level had a significant effect on feed requirements which paralleled the performance in daily gains. In the first experiment, terramycin (but not aureomycin) significantly increased the rate of gain of the pigs during the 36- to 75-lb. period. However, this effect had disappeared by the time the pigs reached 200 lbs. Although the pigs fed aureomycin or terramycin required 21 and 18 lbs. less feed per 100 lbs. of gain respectively, these differences were not statistically significant. In the second experiment, the feeding of aureomycin significantly increased the daily gains and feed efficiency of the pigs for the entire feeding period, but not for the 31- to 75-lb. period. The effect of protein levels and antibiotic feeding on carcass measurements will be reported separately. Copyright © . .