The Effect of Virginiamycin on Gilt Productivity

Abstract

A field trial to demonstrate the effect of cirginiamycin (VM) on sow productivity under local environment was conducted on a 1,200 sow herd in Suphanburi province. A twin set of gilts was randomly allocated to either control or treatment group. Gilts in the treatment group received gestation and lactation diets containing 40 ppm of VM while gilts in the control group received diets containing none. Gilts were served on their second observed estrus using artificial insemination. The number of services and the sequence of boar used at the mated estrus were forced to be the same within a twin set. A twin set was excluded from this trial if either one returned to estrus, exhibited vaginal discharge of failed to conform with the service rules. The farrowing rates between groups did not differ singnificantly (84.7 VS 82.6, P = 0.7780). The treated gilts produced 1.7 piglets born alive/litter (P=0.000) and 1.6 piglets weaned/litter (P = 0.0044) more than the control gilts. However, the average weaning weight of piglets nursed by the treated gilts was significantly lower (6.28 VS 5.67, P =0.0114). When the treatment factor was withdrawn and the reproductive performance of both groups was followed through the subsequent parity, the averages of weaning to the first service interval (5.54 VS 5.60, P=0.8465), the farrowing rates (75.75 VS 75.75) and the piglets born alive/litter (9.10 VS 9.78, P =0.5575) in both groups became similar.