Low concentrations of a polyphenolic extract from pine bark in high–concentrate diets decrease in vitro rumen ammonia nitrogen but not methane production

This study was conducted to assess the effects of small supplemental doses of a polyphenolic extract from pine bark (PBE) on CH4 output and ruminal fermentation parameters when incubated in batch culture with a high–concentrate diet for 24–h. The data from the dietary substrates supplemented with 0.0, 0.3, 0.6, 0.9, 1.2, 1.5 and 1.8% of PBE were evaluated in a randomized complete block design, and compared using ANOVA followed by Tukey's test and polynomial contrasts. Increasing doses of the PBE caused a linear decrease of the NH3–N concentration (p < 0.001), the potentially degradable dry matter (DM) fraction (p = 0.002), the partitioning factor (p = 0.001), CH4 production and proportion (p = 0.001 and p = 0.029, respectively), although only at 6–h, achieving the lowest productions (p = 0.016) with 1.5 and 1.8% PBE. In contrast, the PBE linearly increased asymptotic gas production (p = 0.007), gas yield (p = 0.004), pH (p = 0.002) and the short–chain fatty acid concentration (p < 0.001) at 24–h. Addition of least 1.5% PBE to high–concentrate diets reduces CH4 production by 31% at 6–h, whereas NH3–N concentration is reduced by 31% at 24–h incubations.