Effect of Feeding Therapeutic Level of Antibiotic at Breeding on Reproductive Performance of Swine

Feeding an antibiotic (tetracycline), at a therapeutic level (0.54 gm. per head per day) for a 10-day to 3-week period beginning 0 to 7 days prior to the start of the breeding season, resulted in a significant increase in the size of the litter farrowed. Antibiotic treated sows and gilts farrowed litters averaging 18.3% larger, and weaned 29.3% larger litters than controls. In addition, 9.3% more of the pigs farrowed were alive at birth.