Background: Fumonisin B1 (FB1) is a secondary metabolite produced mainly by Fusarium verticillioides or Fusarium proliferatum. It poses a huge threat to the sustainable animal industry and human health as well via food chains (egg, meat and milk). Although E. coli-expressed nanobodies are documented for diagnostic applications, nanobodies remain elusive as FB1 detoxifiers in feed and food. Results: In the present study, the E. coli-expressed nanobody was assessed to remove FB1 in fresh milk, embryonated eggs and broilers. Firstly, 2 alpacas received intramuscularly FB1-adjuvanted BSA 6 times, and then the variable domain of the heavy-chain antibody (VHH) of fb1 genes were amplified to clone into the pCANTAB 5 E vector in order to generate a VHH-FB1 phage antibody display library, yielding 3.4 × 10¹⁰ capacity with 96.7% positivity. Afterwards, 5 anti-FB1 nanobodies were expressed and identified. Furthermore, maximal 43.2% FB1 was removed from milk by 1:2000 concentration of nanobody 5 (Nb5). Furthermore, SPF-embryonated eggs were inoculated into albumens with nanobody-treated FB1. The Nb5 group yielded an 83.3% hatching rate, higher body weight, lower gizzard ulceration and fewer FB1 residuals. In order to warrant the above results, 50 broilers aged 10 days were received orally with 20 ppm of FB1 for 20 days. At the same time, birds were fed orally with 50 μg of Nb5 or bivalent nanobody 11 (BiNb11). Finally, the Nb5 group showed a higher relative body weight gain and lower gastric ulcerations and fewer inflammations in the thymus and bursa. Conclusions: Based on the above evidence, the Nb5 nanobody may be considered as an additional FB1 detoxifier, contributing to FB1 decontamination.

As a multifactorial cause, gastric ulceration-mediated diarrhea is widely prevalent in the weaned piglets, impairing pig health and economic benefits. With full implementation of antibiotic stewardship programs in China, Bacillus cereus (B. cereus) and Aspergillus fumigatus (A. fumigatus) were identified frequently in porcine feedstuffs and feeds of the animal industry. Association between feed-borne B. cereus and frequent diarrhea remains unclear. In the present study, we conducted a survey of B. cereus and A. fumigatus from feeds and feedstuffs in pig farms during hot season. Interestingly, B. cereus, B. subtilis, B. licheniformis and B. thuringinesis were isolated and identified from piglets’ starter meals to sow feeds, accounting for 56.1%, 23.7%, 13.7% and 6.5%, respectively. Obviously, both B. cereus and B. subtili were dominant contaminants in the survey. In an in vitro study, Deoxynivalenol (DON) contents were determined in a dose-dependent manner post fermentation with B. cereus (405 and DawuC). Subsequently, 36 weaned piglets were randomly assigned to four groups and the piglets simultaneously received the combination of virulent B. cereus (Dawu C) and A. fumigatus while animals were inoculated with B. cereus (Dawu C), A. fumigatus or PBS as the control group. Clinically, piglets developed yellow diarrhea on day 5 and significant reductions of relative body weight were observed in the B. cereus group, and co-infection group. More importantly, IgG titers against Classical swine fever virus (CSFV) and Porcine epidemic diarrhea (PED) were reduced dramatically during 14-day observation in co-infection group, the B. cereus (Dawu C) group or the A. fumigatus group. However, lower Foot and mouth disease (FMD) -specific antibodies were reduced on day 7 compared to those of the control group. Additionally, lower lymphocyte proliferations were found in the B. cereus group and the co-infection group compared to the control group. Postmortem, higher lesions of gastric ulceration were observed in the B. cereus group and the co-infection group from day 7 to day 14 compared with those of the A. fumigatus group and the control group. Compared to the A. fumigatus group, higher DON contents were detected in the stomach inoculated with B. cereus and the co-infection with A. fumigatus. In conclusion, our data support the hypothesis that B. cereus might be associated with severe diarrhea by inducing gastric ulcerations and A. fumigatus might aggravate immune suppression, threating a sustainable swine industry. It is urgently needed to control feed-borne B. cereus contamination.