Bacillus subtilis PB6 Supplementation in Weaned Holstein Steers During an Experimental Salmonella Challenge.
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abstract
To evaluate the effects of a patented Bacillus subtilis probiotic, weaned Holstein steers, not shedding Salmonella (n=40; 90kg), were supplemented (CLO) or not (CON) with CLOSTAT (13 g/hd per day; Kemin Industries, Des Moines, IA) in a starter ration for 35 d. The calves were assigned to one of four treatments in a 22 factorial design with CLO and CON calves that were orally administered Salmonella (STM) or not (NoSTM). Calves were challenged with 1.6106 colony-forming unit (CFU) Salmonella Typhimurium (resistant to 50g/mL nalidixic acid) in 1L of milk replacer on day 0. Blood samples were collected through jugular catheters every 6h for 96h, and body temperature was measured every 5min through indwelling rectal temperature recording devices. Five calves from each treatment were harvested 48h postchallenge, and the remaining calves were harvested 96h postchallenge. During necropsy, tissues were collected for the isolation and quantification of the inoculated STM from various tissues. The CLOSTM group had reduced STM concentrations in the jejunum, ileum, and transverse colon 48h after the challenge (p0.03), but were not different 96h postchallenge (p>0.05). Decreased (p<0.01) pyrexia was observed after the challenge in CLOSTM calves when compared with CONSTM calves. White blood cells and lymphocyte counts were increased (p0.05) in CLOSTM calves after the challenge in comparison with other treatments. In calves given STM, the CLO group had greater feed intake before and after the challenge (p<0.01) compared with the CON group. Increased serum IL-6 and IFN- concentrations were observed in the CONSTM group compared with other treatments. Overall, CLO reduced Salmonella presence and concentrations in gastrointestinal tissues while simultaneously reducing the severity of the challenge as indicated by blood parameters and the reduced febrile response.
