Cinética de fermentação e parâmetros ruminais de animais alimentados com dietas contendo níveis de inclusão de torta da amêndoa de castanha-do-pará

Abstract

The inclusion effect of 0 (control), 15, 30, 45, 60, and 100% dry matter (DM) of Brazil nut (Bertholletia excelsa Bonpl.) cake (BNC) aiming at replacing corn silage was assessed on fermentation kinetics and effective degradability (ED) by means of in vitro gas production at 3, 6, 9, 12, 24, 48, 72 and 96 h. A randomized block design was used with six treatments, three blocks, and two replications per block. France’s model was fit to the data. An in vivo experiment, conducted in fistulated ovine, assessed the effects of BNC inclusion levels of 0, 15, 30, and 45% DM replacing corn silage on ruminal parameters. Ruminal fluid samples were collected postprandial at 8, 10, 12, 14, 16, and 18 h for determining the concentrations of short-chain fatty acids (SCFA), pH, and N–NH3 . A completely randomized design with repeated measures in time was used, with four treatments and three replications. Results of acetate, propionate, butyrate, acetate to propionate ratio, pH, and NH3 were submitted to analysis of variance and regression (linear and quadratic) considering treatment, time and interaction of both. In addition, the F test with a 5% (P < 0.05) significance level was applied to the data. Fermentation kinetics pattern and ED presented a linear decreasing (P < 0.05), which means a decrease in total gas production at each coproduct inclusion level. No interaction effect between treatment and time was observed for total SCFA (P > 0.40), acetic acid (P > 0.41), propionic acid (P > 0.85), butyric acid (P > 0.62) and pH (P > 0.57). BNC replacements of 0, 15, 30 and 45% did not change (P > 0.05) total SCFA concentration, as well as acetic acid concentration in ovine. When including 45% DM of BNC, concentrations (mMol/100 mL) of propionic (P < 0.001) and butyric (P < 0.022) acids was reduced in the ruminal fluid. The highest concentrations at measurement times were observed 4 hours after feeding. The pH values presented a quadratic effect on both inclusion (P < 0.001) and time (P < 0.001). An interaction was observed between treatment and time for N–NH3 concentration (mg/ml) (P < 0.001) and acetic to propionic acids ratio (P < 0.014). Fermentation kinetics was negatively affected by Brazil nut cake inclusion to corn silage-based diet. Therefore, the use of this coproduct is recommended associated with non-structural carbohydrate sources.