PSX-25 The Fecal Metabolome Differs Between Nelore Bulls Fed Pre- and Post-Feedlot Diets: Initial Results

Abstract The objective of this study was to evaluate the fecal metabolome of Nelore bulls (Bos taurus indicus) fed pre- and post-feedlot diets. In pre-feedlot, 21 animals belonging to the Nelore Qualitas breeding program aged 666 ± 68 days old, and 534.5 ± 34.2 kg of body weight were allocated to one pen for 15 days. The pre-feedlot diet contained corn silage (80%) and sugarcane bagasse (20%). Next, the bulls (546.0 ± 41.2 kg of body weight) were submitted into a finishing stage in feedlot for 56 days. During the post-feedlot diet contained wet grain corn (44.6%), corn silage (27.6%), citrus pulp (11.9%), peanut bran (8%), sugarcane bagasse (4.9%), premix (1.8%) and urea (1.2%) twice a day with ad libitum access in Intergado electronic troughs (Intergado Ltda., Contagem, Minas Gerais, Brazil). Pre- and post-feedlot fecal samples were collected directly from the rectal ampulla of each bovine and stored in a -80°C freezer for metabolomic assays by Nuclear Magnetic Resonance analysis (1H NMR). The metabolites were identified, quantified and data processing using the Chenomx NMR Suite 8.6 (Chenomx Inc., Edmonton, AB, Canada) and MetaboAnalyst 5.0 (http://www.metaboanalyst.ca). We identified and quantified 57 and 55 metabolites in the fecal samples of the bulls fed pre- and post-feedlot diet, respectively. We observed that 39 metabolites differed (P < 0.05) between pre- and post-feedlot diet. The 2-phenylpropionate, caprylate, fumarate, deaminotyrosine, gamma-glutamyl phenylalanine, NADH, thymidine and pantothenate were observed only in the pre-feedlot diet. However, acetamide, 2-oxoglutarate, uracil, xanthine, trimethylamine and demethyl sulfone were consumed exclusively post-feedlot diet. Our multivariate analyses demonstrated that the fecal metabolite profiles of the Nelore bulls fed pre- and post-feedlot diet were different. The first two components of principal component analysis (PCA) explained 86.1% of the total data variance (PC1 = 77.6%; PC2 = 8.5%). Likewise, the partial least squares discriminant analysis (PLS-DA) explained 85.5% of the data variance with the first two components (component 1 (74.4%) vs. component 2 (8.1%)). Three fecal metabolites (acetate, butyrate, and propionate) with variable importance in the projection (VIP scores over 1.0; P