Effects of pomegranate peel extract on ruminal and post-ruminal in vitro degradation of rumen inoculum of the dairy cow

This experiment was carried out to study the effect of water extracted pomegranate peel extract (PE) on ruminal protein degradation and post-ruminal digestion in the dairy cow. PE was added at six levels of total phenolics (g/kg of the basal diet); 3.75 (PE1); 4.4 (PE2); 5.05 (PE3); 5.70 (PE4); and 6.35 (PE5). Rumen degradable crude protein (rdCP) decreased with PE addition (L < 0.0001), but total CP degradability (tdCP) was not affected. Compared to PE0, PE2, and PE3 diets showed higher (L = 0.054, Q = 0.029) digestibility of bypass CP (dBCP). Increasing levels of PE resulted in a decrease in proteolytic bacteria numbers (p < 0.0001). At PE4 and PE5 levels, total VFA and acetate concentrations linearly decreased compared to PE0. PE inclusion lowered the acetate:propionate ratio (L = 0.0001) and Ammonia-N production after 24 h (L = 0.0008) of incubation. The total number of protozoa, genera Dasytricha and Isotricha, and subfamilies Entodiniinae, Diplodiniinae, and Ophrioscolecinae decreased with increasing dietary PE concentration (p < 0.0001). The results suggest that all levels of PE addition reduce the protozoal population and Ammonia-N concentration. All PE levels slowed down protein degradation in the rumen but PE2 and PE3 showed the greatest effect.