Effects of dietary supplementation of antimicrobial peptide-A3 on growth performance, nutrient digestibility, intestinal and fecal microflora and intestinal morphology in weanling pigs

In this study, effects of dietary supplementation of the antimicrobial peptide-A3 (AMP-A3) on growth performance, coefficient of total tract apparent digestibility (CTTAD) of nutrients, serum immunoglobulins, intestinal and fecal microflora and intestinal morphology in weanling piglets were evaluated when used as a substitute to the antibiotics. A total of 240 weanling piglets (Landrace × Yorkshire × Duroc, initial body weight (BW): 5.74 ± 0.38 kg) were randomly allotted to 4 treatments on the basis of BW. There were 4 replicate pens in each treatment with 15 pigs per pen. The dietary treatments were: PC (positive control; basal diet + 1.5 g apramycin/kg diet) and AMP-A3 (basal diet supplemented with 0, 60 and 90 mg AMP-A3/kg diets). The experimental diets were fed in a meal form for 2 phases (d 0-14, phase I and d 15-28, phase II post-weaning). Pigs fed the PC diet had greater (P<0.05) overall average daily gain (ADG), average daily feed intake (ADFI) and the CTTAD of crude protein (CP, phase I) and dry matter (DM) and CP (phase II) than pigs fed the AMP-A3 diet. Increasing levels of dietary AMP-A3 linearly improved (P<0.05) overall ADG and CTTAD of DM and CP (phase I and II). Pigs fed the PC diet had lower (P<0.05) coliforms (cecum and feces) and total anaerobic bacteria (TAB, cecum) than pigs fed the AMP-A3 diet. When pigs offered increasing levels of the AMP-A3 diets, there was a linear decline (P<0.05) in TAB, coliforms and Clostridium spp. in the ileum, cecum and feces (d 14 and 28). Pigs fed the PC diet had lower (P<0.05) crypt depth and greater (P<0.05) villus height to crypt depth ratio (VH:CD) of the jejunum than pigs fed the AMP-A3 diets. Increasing levels of AMP-A3 in the diets of pigs increased (linear, P<0.05) villus height and VH:CD and decreased (linear, P<0.05) crypt depth of the duodenum and jejunum. Dietary treatments had no effect (P>0.05) on the coefficient of ileal apparent digestibility of amino acids and serum immunoglobulin concentrations. The results obtained in the present study indicate that the AMP-A3 had beneficial effects on growth performance, CTTAD of nutrients, intestinal morphology and intestinal and fecal microflora and can be used as a potential alternative to antibiotic growth promoters in weanling pigs.