The effect of dietary protein supply on the performance and risk of post-weaning enteric disorders in newly weaned pigs
The effect of dietary protein supply, as manipulated by both crude protein content and/or substitution of existing ingredients, mainly soya (SOYA), with the more digestible dried skimmed milk powder (DSMP), and the consequences of removing in-food antimicrobial growth promoters (AGPs) on the performance and risk of post-weaning enteric disorders (PWED) in newly weaned pigs was investigated. Pigs weaned at 28.7 +/- 3.45 days of age (no. =49) were individually housed in an environmentally controlled room and assigned to one of seven dietary treatments; a 3x2 factorial combination of dietary protein content (130, 180 and 230 g crude protein (CP) per kg) and main protein source (DSMP and SOYA), plus an additional control containing 230 g CP per kg, DSMP and in-food AGPs (ZnO, CuSO4 and avilamycin). Individual food intake, faecal score (FS), cleanliness score (CS) and health score (HS) were taken daily, and live weight and faecal samples were taken on days 0, 4, 7, 11, 12, 13 and 14. All animals were slaughtered on day 14 to examine variables describing aspects of gastro-intestinal health. Increasing CP content and the removal of AGPs both led to a significant increase in faecal fluidity and contamination although there was no effect on HS. There was no effect of DSMP inclusion on FS, CS or HS. Increasing CP content led to an increase (hairspP < 0.05) in the number of coliforms in faecal and proximal colon (PC) samples taken at slaughter and a decrease (hairspP < 0.01) in the lactobacilli to coliform ratio (L:C) in the PC. Increasing CP content had no effect on average daily food intake (ADFI) but led to improvements in average daily gain (ADG) (hairspP < 0.001) and food conversion ratio (FCR) (hairspP < 0.001) over the whole trial period. The inclusion of DSMP had no effect on performance during the 1st week, but animals on the DSMP diets had improved ADG (hairspP < 0.05) and FCR (hairspP < 0.01) compared with those on the SOYA diets in the 2nd week. The inclusion of AGPs increased ADFI (hairspP < 0.05) and ADG (hairspP < 0.05) but had no effect on FCR over the whole trial period. The results indicate that in the absence of AGPs both growth performance and the risk of PWED increased as protein supply was increased. The increased risk of PWED was associated with an increased fluidity of faeces, a reduction in the L:C ratio and an increase in intestinal pH. Consequently, it is important to balance the trade-off between maximizing performance and minimising the risk of PWED through manipulating protein supply, particularly in an environment where AGPs are no longer permitted.