Bioavailability of aflatoxin B1 and ochratoxin A, but not fumonisin B1 or deoxynivalenol, is increased in starch-induced low ruminal pH in nonlactating dairy cows

Pantaya, D. and Morgavi, D.P. and Silberberg, M. and Chaucheyras-Durand, F. and Martin, C. and Suryahadi, Suryahadi and Wiryawan, K.G. and Boudra, H. (2016) Bioavailability of aflatoxin B1 and ochratoxin A, but not fumonisin B1 or deoxynivalenol, is increased in starch-induced low ruminal pH in nonlactating dairy cows. Journal of Dairy Science, 99 (12). pp. 9759-9767. ISSN 00220302

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Abstract

High-production dairy and beef systems require diets rich in starch. This practice may induce ruminal acido- sis and also increase exposure to mycotoxins because starches in starch-rich diets are the main vehicles of mycotoxin contamination. The aim of this study was to investigate the effects of low ruminal pH on the bioavailability of 4 major mycotoxins [i.e., aflatoxin B1 (AFB1), ochratoxin A (OTA), deoxynivalenol (DON), and fumonisin B 1 (FB1)]. Eight nonlactating dairy cows fitted with rumen cannulas were used in a double crossover experiment. The trial was divided into 4 pe- riods with 2 periods per crossover. Cows were divided into 2 groups receiving a low (15% dry matter basis) and high-starch diet (30.8%) with and without live yeast supplementation (1 × 10 10 cfu per cow) in the first and second crossover, respectively. At the end of each period, cows received a single dose of mycotoxin- contaminated feed containing 0.05, 0.2, 0.24, and 0.56 mg of AFB1, OTA, DON, and FB1 per kg of feed, respectively. The fecal and urinary excretion of myco- toxins and their metabolites was monitored for up to 48 h postdosing. As expected, ruminal pH decreased in cows fed the high-starch diet. The high-starch diet in- creased the bioavailability of OTA and AFB1. Urinary excretion of OTA 24 h after mycotoxin administration increased 3-fold in the high-starch diet, correlated with lower fecal excretion. Similarly, a decrease in fecal ex- cretion of AFB1 was accompanied by an increase in urinary excretion of its major metabolite, aflatoxin M1, 48 h after mycotoxin administration. In contrast to AFB1 and OTA, the bioavailability of DON and FB1 remained unchanged. Yeast supplementation had no effect on the excretion balance of these 2 mycotoxins. In conclusion, these results show that high-starch diets increased the bioavailability of OTA and AFB1, most probably through the lowering effect on ruminal pH. This greater bioavailability potentially increases the toxic effects of these mycotoxins. Key words: mycotoxin, low ruminal pH, dairy cow, live yeast supplementation

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