The fermentation kinetics and effective degradability (ED) brazil’s nut (Bertholletia excelsa Bonpl.) - (BN) were evaluated in the proportions 0 (control), 15, 30, 45, 60 and 100% dry matter in substitution of corn silage (CS) by in vitro gas production in the times 3, 6, 9, 12, 24, 48, 72 and 96 hours. The experimental design for the gas production was in randomized blocks with six treatments, three blocks and two repetitions per block. To estimate of ruminal kinetics fermentation parameters of each treatment, the model of France et al. (1993) was fitted to the data. In in vivo experiment, we evaluated the ruminal parameters of sheep fed 0, 15, 30 and 45% (MS) TAC, and corn silage. The rumen fluid collections to determine the concentration of SCFA, pH and N-NH3 were held at 08h00, before the diet supply, and at 10h00, 12h00, 14h00, 16h00 and 18h00, post-prandial. The design was completely randomized with repeated measures, with four treatments and three replications. The variables results: acetate, propionate, butyrate, acetate: propionate ratio, pH and NH3 were subjected to analysis of variance and regression (linear and quadratic) considering treatment time and the interaction of both. We used the F test, with significance level of 5% (P<0.05). The standard kinetic fermentation and ED was declining linear (P<0.05), reducing total gas production at each level of coproduct addition. There was no significant interaction between treatment vs time for all SCFA variables (P>0.40), acetic acid (P>0.41), propionic (P>0.85), butyric acid (P>0.62) and pH (P>0.57). There was also effect on the total concentration of SCFA (P>0.75) nor in acetic acid (P>0.07) among the treatments. The concentration of propionic and butyric acids mMol/100ml of ruminal fluid reduced (P<0.001) (p<0.022) with the addition of 45% DM TAC. The highest concentrations in the measurement times were observed 4 hours after feeding. The pH values showed a quadratic effect both inclusion (P<0.001) and time (P<0.001). There was interaction (P <0.001) between treatment vs time NH3-N (mg/ml) concentration and the ratio of acetic: propionic acid (P<0.014). It is recommended the use of the TAC, at levels equal to or less than 30%, combined with different carbohydrate sources.
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