Effects of addition of fibrolytic enzymes or butyrate in feedlot diets on metabolic variables of Angus cattle

Abstract

Confined bovine cattle are exposed to high loads of short-chain fatty acids (SCFA), deriving from ruminal fermentation, which can damage the digestive epithelium if it is not developed to promote the removal of such products. Such development is closely related to the absorption of the SCFA produced, especially butyrate, or butyric acid. Thus, the hypothesis raised is that the addition of butyrate generated in the rumen environment, from ruminal fermentation or via dietary supplementation, positively impacts epithelial development as well as other related parameters. This study aims to evaluate the effect of butyrate addition to the ruminal epithelium, as well as on other ruminal and physiological parameters involved. Three Aberdeen Angus cattle will be used; each male, castrated, cannulated in the rumen and with an average initial weight of 690 kg. The experiment will be conducted in a duplicate 3x3 Latin square, totaling 6 experimental periods and lasting 203 days. Each experimental period will consist of 28 days, 14 for adaptation and 14 for finishing, with an interval of 7 days between them, called washout, in which the animals will be released for grazing. The diets will differ only in regard to the food additive used, in accordance with the following treatments: CON) Control (no additives added); ENZ) Use of exogenous enzyme complex (0.01% of DM); BUT) Use of sodium butyrate (0.3% of DM during and adaptation and 0.1% of DM during finishing). The treatment effects will be considered as fixed and the period and animal effects will be considered random. Rumen temperature, pH and oxide-reduction potential will be measured by data loggers, and ruminal fluid samples will also be collected to determine the proportion of short-chain fatty acids, N-NH3 and microbial community composition. Titanium dioxide markers will be added via cannula so that the coefficients of total nutrient digestibility are calculated. On the last day of each experimental period, samples of ruminal papillae will be collected to perform morphometry and gene expression; blood will also be collected, which will occur on the first day as well, and will be used to measure non-esterified fatty acids, insulin and glucose. The data from this study will be analyzed by PROC MIXED by SAS (2003), and the Tukey test will be used to compare averages when necessary, considering the 5% significance level. (AU)