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 x 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 x 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. (C) 2004 Society of Chemical Industry.