Abstract

ALMARAZ-BUENDIA, Isaac et al. Inhibitory effect of selenium concentrations on microbial activity during oat hay in vitro rumen fermentation. Agrociencia [online]. 2018, vol.52, n.4, pp.511-521. ISSN 2521-9766.

Selenium (Se) has been supplied to ruminants in concentrations higher than that of their established tolerable maximum, but its effects on the ruminal fermentation are scarcely documented. Our objective of this study was to evaluate the effect of Se added to in vitro fermentation of oats hay. The treatments were: control, Se20, Se40, Se60 and Se80 which correspond to 0, 20, 40, 60 and 80 mg Se kg-1 MS sodium selenite in the substrate. Oat hay samples (500 mg) were incubated with 40 mL of culture media (rumen fluid, mineral solutions, buffer solution, resazurin and reducing solution) at 39 °C for 72 h, using the gas production technique. The evaluated variables were: accumulated gas volume (AGV), gas production kinetics (maximum volume (V), gas production rate (S) and delay time (L)), methane (CH4), pH, degradation of dry matter (DMS), volatile fatty acids (VFA) and ammoniacal nitrogen (N-NH3). The completely randomized experimental design with repeated measures had seven independent repetitions per treatment. The data were analyzed with the MIXED procedure in the SAS® software. Oat hay fermented with Se60 and Se80 had higher pH and lower AGV, V, S, and CH4 compared to the other treatments (p ≤ 0.05). Se addition did not affect DMS, VFA or N-NH3 (p > 0.05), but these variables linearly decreased with the highest microelement concentrations (p ≤ 0.05). The microbial activity during the in vitro fermentation of oat hay kept constant with 20 and 40 mg Se kg-1 MS; the last concentration may be the maximum limit that guarantees the appropriate in vitro fermentation.

Keywords : sodium selenite; degradation; gas production; methane; volatile fatty acids; ammonia nitrogen.

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