The effects of the periodical use of in-feed chlortetracycline on the reproductive performance of gilts and sows of a commercial pig farm with a history of clinical and subclinical viral and bacterial infections.

The objective of this study was to assess the effects of in-feed chlortetracycline (CTC) as a measure of preventing or minimizing infectious problems of reproductive failure in gilts and sows. In a farm of 400 Large White x Landrace gilts and sows with a clinical history of porcine respiratory and reproductive syndrome (PRRS) virus, the animals were treated with CTC. Treatment consisted of 10 g CTC sow/day for 15 days every 3 months. It improved the health status of sows by decreasing post-farrowing clinical mastitis and vaginal discharges, abortions, return-to-oestrus and irregular return-to-oestrus rates. These beneficial effects had a positive impact on the performance of the litter. More piglets were born live and weaned. These positive effects improved with repeated use of CTC. The serological evidence of PRRS virus, Leptospira spp. and Chlamydia spp. and the subsequent beneficial use of the antimicrobial agent indicate that reproductive failure, possibly resulting from the bacterial agents can be controlled with in-feed use of broad spectrum antimicrobials.