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Effects of different levels of aflatoxin B1 on ruminal digestibility, fermentation profile, and N efficiency of a lactating dairy cow diet using a dual-flow continuous culture system.

F. X. Amaro

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06-24-2020

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Abstract:

W83
Effects of different levels of aflatoxin B1 on ruminal digestibility, fermentation profile, and N efficiency of a lactating dairy cow diet using a dual-flow continuous culture system.
F. X. Amaro*1, M. Pupo1,2, B. C. Agostinho1,3, S. Bennett1, J. Vinyard1, L. Tomaz1,4, R. Lobo1,5, J. A. Cordeiro1, Y. Jiang1, K. G. Arriola1, A. Faciola1, A. T. Adesogan1, D. Vyas1. 1University of Florida Gainesville, Fl, 2Escola Superior de Agricultura Luiz de Queiroz Piracicaba, SP, Brazil, 3Universidade Estadual de Maring� Maringa, PR, Brazil, 4Universidade Estadual Paulista Botucatu, SP, Brazil, 5Universidade de Sao Paulo Pirassununga, SP, Brazil.

The objective of this study was to evaluate the effects of increasing doses of aflatoxin B1 (AfB1) on ruminal nutrient digestibility, fermentation profile, and microbial protein synthesis from a total mixed ration (TMR) using a dual-flow continuous culture system. Eight fermentor vessels were used in a replicated 4 � 4 Latin square design with 10-d periods (7 d adaptation and 3 d sample collection). Treatments were Control; no AfB1, AfB50; 50 ppb of AfB1 equivalent to 5.35 μg/d of AfB1, AfB100; 100 ppb of AfB1 equivalent to 10.7 μg/d of AfB1, and AfB150; 150ppb of AfB1 equivalent to 16.05 μg/d of AfB1. Fermentors were fed twice daily (107 g DM/d) with the TMR. The total dose of AfB1 for respective treatments was diluted in ethanol and applied to the fermentors along with feeding. The basal TMR had the same nutrient composition across all treatments (15.9% CP, 26.4% aNDF, 30.3% starch and NEL of 1.61 Mcal/kg). Rumen fluid was sampled, and pH measured from the vessels at 0, 1, 2, 4, 6 and 8 h after feeding for 2 consecutive days. 15N was used as a marker to assess N efficiency. Data were analyzed using the GLIMMIX procedure of SAS. Linear, quadratic, and control vs. treatment contrasts were tested. Treatments did not affect nutrient digestibility (P > 0.05; DM, OM, CP, NDF, ADF), pH or ammonia-N (NH3-N) concentration. However, sampling time affected pH and NH3-N concentration (P < 0.01) with the lowest pH (5.69) and greatest NH3-N concentration (20.65 mg/dL) observed at 4 h and 1 h post-feeding, respectively. Total VFA concentration was not affected by treatment; however, sampling time did (P < 0.01). Acetate (50.1 vs. 48.9%), propionate (27.5 vs. 26.3%) and acetate-to-propionate ratio (A:P) (1.93 vs. 1.85) were greater for control compared with AfB1 treatments (P < 0.01). Bacterial N flow and N efficiency were not affected by treatments. In conclusion, AfB1 addition to the TMR decreased molar proportion of acetate, propionate and A:P ratio without affecting nutrient digestibility or N efficiency.

Keywords: aflatoxin, in vitro, microbial protein.

Biography: Felipe Xavier Amaro was born in Brazil, got his bachelor's degree in animal sciences from Universidade Federal de Vicosa in 2016. He joined the student body of the University of Florida in 2017 and got his master's degree in 2018, since then he has been working on his Ph.D. researching nutritional strategies to improve feed efficiency in dairy cattle.