<i>In vitro</i> rumen fermentation and protein protection of canola and soybean meals using tannin extract from <i>Bauhinia hookeri</i>

Tannins are natural compounds known to suppress methane-producing microbes and bind dietary proteins in the rumen, potentially improving nitrogen use efficiency. This study evaluated the effects of condensed tannin extract (TE) from <i>Bauhinia hookeri</i> hay on in vitro rumen fermentation and protein degradation of canola and soybean meals. We hypothesised that TE would suppress methane production and enhance protein protection in both meals. Each meal was treated with 0%, 2%, 4%, or 6% TE in dry matter basis and incubated for 24 h using the ANKOM gas production system. Total gas production was reduced in treated canola meal by 16.4% at 2% TE (<i>P</i> = 0.014), 30.1% at 4% TE (<i>P</i> < 0.001), and 52.7% at 6% TE (<i>P</i> < 0.001). Methane production was unaffected at 2% TE (<i>P</i> = 0.267) but declined by 37.2% at 4% TE and 40.4% at 6% TE (<i>P</i> < 0.001). Lag time before gas production began increased in both feeds (<i>P</i> < 0.05). Total volatile fatty acid (VFA) concentration of soybean meal was unchanged at 2% and 4% TE but declined at 6% TE (<i>P</i> = 0.006). Soluble protein (fraction 'a') decreased in both meals with TE inclusion (<i>P</i> < 0.001), while the slowly degradable protein fraction ('b') increased (<i>P</i> < 0.05). The degradation rate of fraction 'b' was reduced across all TE-treated groups (<i>P</i> < 0.05). These results suggest that TE from <i>Bauhinia hookeri</i> hay can reduce methane emissions and protect protein from excessive ruminal degradation. The 4% inclusion rate consistently showed optimal results across fermentation and protein parameters, making it a promising level for practical application.