Interaction between lactose levels and antimicrobial growth promoters on growth performance of weanling pigs

In experiment 1, 224 pigs (initially 8.85 kg and 28 ± 2 days of age) were used in a 2 × 2 factorial arrangement of treatments to investigate the interaction between lactofeed (LF70) (860 g kg −1 whey permeate, 140 g kg −1 soya bean meal) level (175 g kg −1 and 350 g kg −1 ) and avilamycin (0 and 40 mg kg −1 ) inclusion in piglet starter diets. Pigs were fed starter diets from day 0 to day 22 and a transition diet was fed from day 23 to day 39. The inclusion level of LF70 in the transition diet was 75 g kg −1 and 150 g kg −1 . Pigs fed 350 g kg −1 LF70 had a higher daily gain (ADG) ( p < 0.01) and an improved feed conversion ratio (FCR) ( p < 0.05) during the starter period than the pigs fed 175 g kg −1 LF70. Pigs fed medicated diets had a higher ADG ( p < 0.05) and an improved FCR ( p < 0.05) than the non‐medicated fed pigs during the starter period. There was an increase in feed intake (AFI) ( p < 0.05) during the transition period with increasing levels of LF70. There was an improvement in FCR during the transition period with the inclusion of avilamycin ( p < 0.01). There was a significant interaction ( p < 0.01) between LF70 and avilamycin for ADG during the transition period. The inclusion of avilamycin at 175 g kg −1 LF70 inclusion had no effect ( p > 0.05) on ADG. However at 350 g kg −1 LF70 inclusion the pigs offered medicated diets had a higher ADG ( p < 0.001) compared with non‐medicated diets. In experiment 2, 224 pigs (initially 8.85 kg and 28 ± 2 days of age) were used in a 2 × 2 factorial to investigate the interaction between LF70 level (175 g kg −1 and 350 g kg −1 ) and zinc oxide (ZnO) (0 and 3.1 g kg −1 ) inclusion in piglet starter diets. The inclusion level of LF70 in the transition diet was 75 g kg −1 and 150 g kg −1 and of ZnO was 2 g kg −1 . There was a significant increase ( p < 0.05) in ADG with increasing levels of LF70 during the starter period. The inclusion of ZnO during the starter period resulted in an increase in ADG ( p < 0.001) and FCR ( p < 0.05) compared with no ZnO inclusion. Neither the inclusion of zinc oxide not of LF70 had an effect ( p > 0.05) on performance during the transition period. In conclusion the supplementation of starter diets with increasing levels of LF70, ZnO and avilamycin resulted in increased ADG and improved FCR.