Effect of direct fed microbial Bacillus subtilis C-3102 on enteric health in nursery pigs after challenge with Porcine Epidemic Diarrhea Virus (PEDv)

This study examined the effects of feeding Bacillus subtilis C-3102 (Calsporin® Calpis Co. Ltd., Japan) at the target inclusion rates of 0 CFU/g, 500 000 CFU/g and 1 000 000 CFU/g on intestinal health in weaned pigs after challenge with Porcine Epidemic Diarrhea virus (PEDv).

A two by three factorial design composed of three diets containing 0 CFU/g or 500 000 CFU/g or 1 000 000 CFU/g of Calsporin® and PEDv or sham challenge was conducted. Pigs were 14 days old at the start of the study and PEDv naïve. Ten pigs were randomly allocated to each treatment group and were housed in groups of five. Pigs were fed the treatment diets for 23 days. On day 19, pigs were challenged with PEDv-positive or - negative cell culture by gavage and necropsied at four days post inoculation (dpi). Five small intestine segments were collected per pig using a standardized technique. Histopathology slides were prepared for measurement of villus to crypt height ratios (VCR) and atrophic enteritis (AE) scoring for each section. PEDv immunohistochemistry (IHC) was performed on all slides and semi-quantitatively scored based on the percentage of enterocytes showing a positive signal. Atrophic enteritis scores were based on the presence and severity of enteritis. All scoring was completed by a single blinded veterinary pathologist. Average daily gain (ADG) and mortality was compared across treatment groups at four dpi. Responses were analyzed using linear mixed models. Comparisons among groups were assessed using F-tests followed by Tukey's t-tests for multiple comparisons. Differences were considered significant at the level of P < 0.05. All analysis was performed on SAS® 9.4.

There were significant differences in IHC, AE and VCR between PEDv positive and PEDv negative pigs fed 0 CFU/g Calsporin®. Within PEDv positive groups, there were significant reductions in IHC and AE between pigs fed 0 CFU/g Calsporin® and treatment groups that did receive Calsporin®. VCR was greater in PEDv positive pigs fed Calsporin compared to pigs on the 0 CFU/g diet. There were no significant differences in average daily gain and mortality between any groups.

The findings from this study support an association between administration of Calsporin® and improved IHC scores, histopathology and villus to crypt ratios in nursery pigs challenged with PEDv compared to cohorts that did not receive Calsporin®. The impact of these parameters on morbidity, mortality, ADG and feed efficiency during the entire fattening period is unknown and should be assessed with an additional study of longer duration and larger sample size.

Disclosure of Interest: None Declared.