RUMEN DEGRADATION AND POST-RUMINAL DIGESTION OF PALM KERNEL BY-PRODUCTS IN DAIRY-COWS

Rumen degradation characteristics and digestion post-rumen were measur ed in seven (five expellers and two meals) samples of palm kernel by-p roducts using four cannulated (rumen and distal duodenum) dairy cows a nd nylon bag techniques.The by-products were selected to provide varia tion in chemical composition and in vitro digestibility. All samples c ontained high levels of cell wall constituents (70-80% of the fat-free organic matter) and 16-22% protein. The rumen undegradable fraction o f neutral detergent fibre (NDF) varied between 23 and 37%; degradation of the NDF fraction was preceded by a lag phase, which was longest in the meals. Rumen degradation of the protein fraction was slow, especi ally for two Nigerian samples. The meals displayed larger fractions of rumen undegradable protein than the expellers. This fraction was sati sfactorily predicted by a univariate relationship with in vitro digest ion of protein (pepsin). Variation in protein degradation could not be satisfactorily accounted for by laboratory analyses using fungal prot eolytic enzymes alone. The estimated high level of rumen escape protei n may be partly attributable to microbial contamination. Post-ruminal digestion of the escape protein varied between 83 and 92% and correlat ed strongly with in vitro (pepsin) protein digestibility. Calculations suggest a slow rate of outflow from the rumen of both cell wall and p rotein constituents in palm kernel by-products.