THE EFFECT OF VIRGINAMYCIN SUPPLEMENTATION IN SOW DIETS ON THE REPRODUCTIVE-PERFORMANCE OF THE GILT SOW/

This trial investigated the effects of virginiamycin on sow and litter performance. Virginiamycin was added to the sow diet during the perio d of gestation and lactation at the levels of 0, 40 and 60 mg/kg, thro ughout two breeding cycles. Virginiamycin did not significantly affect sow weight change during gestation or lactation, or litter size and w eight; there were no significant effects on food consumption (P > 0.05 ). However, when added at a level of 40 mg/ kg virginiamycin tended to produce a better condition of sows which resulted in a significant re duction of replacement rate (P < 0.05), even though the proportion of gilts culled in the treated and untreated groups was high. The most ev ident result was a significantly shorter weaning-to-conception interva l for the virginiamycin group at the end of the second reproductive cy cle (first period, 5.9 days less than the control group, 2.5 days less than the 60 mg/kg group; second period, -9.5 days v. control group, P < 0.05, and -7.1 days v. 60 mg/kg group, P < 0.05), allowing a numeri cal improvement in productivity. Piglet performance was not significan tly improved by the use of virginiamycin even though there was an evid ent trend in favour of the 40 mg/kg group which presented a higher pro portion of heavier piglets (P < 0.05) and a reduction of pre-weaning m ortality. A significant quadratic regression was found for weaning-to- conception interval and numeric productivity, indicating that the dosa ge more efficient to improve these parameters was 32 mg/kg. The result s obtained in the virginiamycin 60 group were generally inferior to th ose of the 40 mg/kg group and also to the control group and seem to de monstrate that the 60 mg/kg dosage was too high.