Estimation of digesta kinetics of different particle size fractions using rumen evacuation technique in dairy cows fed red clover-grass silage.

摘要

Ruminal kinetic parameters of different particle size fractions were estimated using four lactating dairy cows in a 4x4 Latin square experiment. The cows were fed with red clover-grass silage solely. Ruminal contents and faeces were divided into six particle size fractions by wet sieving. Indigestible (iNDF) and potentially digestible (pdNDF) neutral detergent fibre were separated by a 12 day ruminal in situ incubation. Particles >2.5 mm formed the highest dry matter, iNDF and pdNDF pools in the rumen. Passage rates of iNDF and pdNDF increased with decreasing particle size. Particle breakdown in the rumen was a relatively slow process (0.041 h-1). Contribution of particle breakdown to turnover of different particle size fractions of rumen iNDF decreased with decreasing particle size, while the contribution of passage increased. It is suggested that the accumulation of iNDF in the rumen is higher than generally observed with grass-based diets and pdNDF is rapidly digested.