Abstract

DOMINGUEZ-ORDONEZ, María G. et al. Evaluation of nutritional methods to reactivate preserved ruminal inoculum assessed through in vitro fermentation kinetics and forage digestibility. Rev. mex. de cienc. pecuarias [online]. 2019, vol.10, n.2, pp.315-334. ISSN 2448-6698.  https://doi.org/10.22319/rmcp.v10i2.4483.

This study evaluated the effect of the media and pre-incubation time for reactivating preserved ruminal inoculum, assessed through in vitro fermentation kinetics and dry matter digestibility (IVDMD). In the first experiment, treatments were 1) CONTROL, fresh ruminal fluid, 2) LOW24, inoculum reactivated by 24 h pre-incubation in a basal culture solution, 3) MODE24, inoculum reactivated by 24 h pre-incubation in basal culture solution, yeast extract and peptone from casein; and 4) HIGH24, inoculum reactivated by 24 h pre-incubation in basal culture solution, yeast extract, peptone from casein and carbohydrates. In the second experiment, treatments evaluated were 1) CONTROL, fresh ruminal fluid, and 2) HIGH12, similar to HIGH24 but inoculum was pre-incubated for 12 h. Each experiment included three replicates. Maximum gas volume (Vm), lag phase (L), gas production rate (S) and IVDMD were measured using four fermentation substrates. Main effects of inoculum and fermentation substrate, and interactions, were analyzed. Compared to CONTROL, Vm, L and S were negatively affected (P<0.01) by preservation of inoculum. However, HIGH24 displayed an improvement (P<0.01) in fermentation kinetics and IVDMD compared to MODE24 or LOW24. In the second experiment, HIGH12 displayed lower (P<0.01) IVDMD at 72 h compared to CONTROL. Alfalfa and orchardgrass had higher (P<0.01) Vm and IVDMD compared to cocuite and guinea grass. Overall, reactivation of preserved ruminal inoculum by pre-incubation for 24 h in a medium containing yeast extract, peptone from casein and carbohydrates performed better compared to reactivation by pre-incubation for 12 h; however, fermentation kinetics and IVDMD were still depressed compared to fresh ruminal fluid.

Keywords : Forage digestibility; Fermentation; Preservation; Ruminal inoculum.