Effects of chlortetracycline administration on the health status and performance of sows: Results of a field trial

Objectives: To investigate the effects of in-feed chlortetracycline (CTC) during lactation on health status and reproductive performance of gilts or sows in a herd with a history of porcine reproductive and respiratory syndrome; to evaluate health status and performance of the piglets born to these females; and to investigate health status and reproductive performance of the same sows during the subsequent lactation period, when no in-feed CTC was administered. Methods: Two groups of 200 gilts or sows were monitored for two consecutive breeding cycles (phases). During Phase 1, the CTC+ group received CTC in the feed (10 g per animal daily) from 5 days before farrowing until the first service after weaning. The CTC- group received non-medicated feed. During Phase 2, both groups received non-medicated feed. Results: Rates of occurrence of poor appetite and vaginal discharges were lower for the CTC+ group during both phases, and rates of occurrence of clinical mastitis, anestrus, and returns-to-estrus were lower for CTC+ sows in Phase 1. The CTC+ sows lost less body weight during lactation, had a shorter wean-to-first estrus interval in Phase 1, and had a shorter interval between Phases 1 and Phase 2 farrowing dates. More piglets were weaned from CTC+ sows, and the piglets had lower mean throughout-lactation diarrhea scores in both phases and heavier weaning weights in Phase 1. Implications: In-feed administration of CTC during lactation improved health and performance of sows and their piglets. The beneficial effects continued during the subsequent lactation, when no CTC was administered