Effects of combined feed additives in diets to support growth performance and intestinal health profile in nursery piglets

Two experiments were conducted to assess the effects of feed additive blends in nursery piglets diets on growth performance, apparent total tract digestibility (ATTD) of nutrients and energy, and intestinal health. In Exp. I, 144 male piglets (6.9 ± 0.04 kg) were allotted randomly into 4 treatments: 1) negative control (NC, no feed additive or antibiotic), 2) positive control (PC, amoxicilin + norfloxacin), 3) simple blend (SB) containing sodium butyrate + dried hydrolyzed yeast + zinc proteinate, and 4) complex blend (CB) containing SB + dried brewery yeast + yeast cell wall, with 12 replicates and 3 animals/pen. Diarrhea occurrence (DO) was monitored daily. On d 44, 9 animals/treatment were slaughtered to collect intestinal samples. Dietary treatments had no effect on growth performance, but piglets fed SB and CB diets showed lower DO than those fed PC diet. Lower DO was observed in starter piglets fed CB and PC diets. Pre-starter piglets fed NC diet showed greater plasma urea concentration than piglets fed PC diet. Starter piglets fed CB diet showed lower eosinophils concentration than those fed NC diet. Piglets on CB diet showed greater stomach pH. Piglets fed the NC diet had greater small intestine weight and lower spleen weight compared to piglets fed the PC and SB diets, respectively. Piglets fed CB diet showed greater jejunum villi than animals on PC and SB diets. Furthermore, greater ileum crypt depth and lower VH:CD ratio was observed in piglets fed SB diet than in CB diet. Piglets fed CB diet showed lower jejunal Enterobacteriaceae count compared to piglets fed PC diet. Goblet cells were more abundant in the jejunum of piglets fed CB diet compared to those in NC diet. Lower tissue necrosis was observed in piglets fed SB and CB diets compared to NC and PC diets. In Exp. II, 24 male piglets (20.3 ± 0.05 kg) were allotted randomly in metabolic cages with the same treatment groups as Exp. I and 6 replicates/treatment. Piglets fed PC and SB diets showed greater ATTD compared to those in CB diet. However, piglets fed SB diet had greater digestible protein and lower digestible OM was observed in piglets fed CB diet. In conclusion, SB did not improve growth performance despite favorable effects on ATTD, but CB was the most promising combination on development of the structure and function of the intestinal epithelium, no detrimental effect on growth performance in nursery piglets.