The effects of direct fed microbials delivered through the feed and/or in a bolus at weaning on growth performance and gut health

Abstract

Weanling pigs ( n = 188) were used in a 5-wk experiment to determine the effects of a bolus of direct fed microbials (DFM) at weaning and/or feeding DFM on growth performance and gastrointestinal histology. Dietary treatments were: 1) basal negative control (NC), 2) Trt. 1 + DFM in a bolus at weaning, 3) Trt. 1 + DFM in the feed for d 1–34, 4) Trt. 1 + DFM in a bolus at weaning, and in the feed for d 1–34, and 5) Trt. 1 + in-feed antibiotics (carbadox, 55 ppm). Dietary antibiotics (Trt. 5) improved ADG ( P < 0.05) during phase 2 (d 7–21) compared to pigs fed DFM (Trt. 3). A bolus dose of DFM at weaning, with or without subsequent DFM in the feed (Trt. 2 and 4), resulted in similar growth performance to pigs on Trt. 1 or 5. However, providing DFM in the feed alone (Trt. 4), resulted in a reduced ADG during phases 1 (d 1–7; P < 0.05) and 2 (d 7–21; P < 0.10) compared to pigs fed the antibiotic diet (Trt. 5). Overall ADFI was higher for pigs fed antibiotics (Trt. 5) compared to all other treatments, except pigs given a bolus dose of DFM at weaning and provided with DFM in the feed (Trt. 4). On d 34, duodenal villus height was higher ( P < 0.05) for pigs fed the antibiotic diet (Trt. 5) compared to pigs receiving the bolus dose of DFM at weaning with no subsequent treatment (Trt. 2). Ileal crypt depths were greater ( P < 0.05) for pigs on the positive control diet (Trt. 5) compared to all other treatments on d 7. Cellular proliferation rates in ileal crypts were increased ( P < 0.05) on d 21 for pigs fed antibiotics (Trt. 5) compared to pigs fed the negative control diet (Trt. 1). On d 34, increased ileal crypt proliferation rates ( P < 0.05) were observed in pigs receiving DFM through the feed (Trt. 4) only compared to pigs receiving the combination bolus and in-feed DFM (Trt. 5) and pigs fed the negative control diet (Trt. 1).