Abstract This study assessed the association between encapsulated nitrate product (ENP) and monensin (MON) to mitigate enteric methane (CH4) in vitro and possible effects on ruminal degradability, enteric fermentation characteristics, and microbial populations. Six treatments were used in randomized complete design in a 2×3 factorial arrangement with two levels of MON (0 and 2.08 mg/mL of buffered rumen fluid) and three levels of ENP (0, 1.5 and 3.0%). The substrate consisted of 50% Tifton-85 hay and 50% concentrate mixture (ground corn and soybean meal). ENP replaced soybean meal to achieve isonitrogenous diets (15% CP). No ENP×MON interaction was observed for any measured variable (P > 0.05) except for the relative abundance of F. succinogenes (P = 0.02) that linearly increased in diets with MON when ENP was added. The ENP addition decreased CH4 production (P < 0.01) without affecting (P > 0.05) truly degraded organic matter nor the relative abundance of methanogens. Hydrogen production was reduced with MON (P = 0.04) and linearly decreased with ENP inclusion (P = 0.02). We concluded that use of nitrate is a viable strategy for CH4 reduction, however, no additive effect of ENP and MON was observed for mitigating CH4 production.

ABSTRACT. The objective of this study was to evaluate the performance and digestibility of diets containing different levels of crude propolis for growing rabbits. Forty-eight New Zealand White rabbits, 43 days old, of both genders, were used, distributed in a completely randomized design. There were four diets with different inclusion levels of crude propolis (0.0; 0.5; 1.0 and 1.5%). There was no statistical difference for performance regarding the inclusion levels of crude propolis (p = 0.85), as well as for the variables dry matter consumption, neutral detergent fiber and acid detergent fiber (p ≥ 0.07). Crude protein consumption showed a statistical difference in relation to gender (p = 0.04): males showed higher consumption. However, final weight, total weight gain, daily weight gain and feed efficiency were not influenced by the addition of crude propolis (p ≥ 0.37). Dry matter digestibility, crude protein, neutral detergent fiber and acid detergent fiber were not influenced by the inclusion levels of crude propolis in the diets (p ≥ 0.12). This study indicates that the inclusion of raw propolis up to 1.5% in the diets does not affect the performance parameters of rabbits.