The effects of restricted floor space allowance and virginiamycin supplementation on the feedlot performance of swine

Abstract

Three series of trials involving 732 pigs were conducted to evaluate the feedlot performance of starter and grower-finisher swine housed under conditions of restricted and adequate floor space allowance when fed diets with and without virginiamycin (11 mg kg −1). In starter Trials 1–4, floor space allowance was altered by housing either 12(0.12 m 2/pig) or 6 (0.24 m 2/pig) pigs in 1.2 × 1.2 m cages. Increasing the number of pigs per cage from 6 to 12 caused depressions in daily gain, in feed intake and in feed efficiency. Virginiamycin supplementation improved daily gain and feed efficiency. In starter Trials 5 and 6, floor space allowance was altered by varying cage size with six pigs per cage across treatments. Decreasing floor space allowance from 0.24 to 0.12 m 2 per pig caused depressions in daily gain and feed efficiency. Virginiamycin supplementation had no significant effect on performance. In grower-finisher Trials 7–9, floor space allowance was altered by varying pen size with 5 pigs per pen across treatments. Decreasing floor space allowance from 0.78 to 0.43 m 2 per pig caused depressions in daily gain, daily feed intake and feed efficiency over the entire trial, but virginiamycin supplementation had no significant effect on performance. The virginiamycin by floor space allowance interaction was significant in only one instance (Trials 1–4) with virginiamycin improving feed efficiency by 6.2% when pigs were housed at a density of 6 per pen, but only by 2.5% when housed at a density of 12/pen. These results show the importance of floor space allowance in relation to performance of starter and grower-finisher pigs, but indicate that the response to dietary virginiamycin was similar under conditions of restricted or adequate space allowance.