Forage species effects on particle digestion kinetics estimated by rumen evacuation or gas production technique

Digestion rate ( provides digestion kinetic information for different particle sizes of grass and red clover silage diets fed to dairy cows. Dietary treatments and described in a companion summary. Ruminal and faecal particles were divided into large (>1.25 mm; LP), medium (1.25-0.315 mm; MP) and small (1.25-0.038 mm; SP) sizes by wet sieving and from all particle size fractions. The pdNDF content in ruminal LP, MP and SP was greater with grass compared to red clover silage diet while indigestible NDF (iNDF) content tended to be greater in LP of red clover compared to grass silage diet. The rumen evacuation, was slower for SP compared to LP and MP of both grass and red clover silage diets. Effective samples decreased in a quadratic manner by decreasing particle size but were not affected by treatment and were lower for faecal samples compared to ruminal samples. Effective ruminal LP and MP was slower but for SP was faster when determined by production compared tokd) is an important determinant of fibre digestion in ruminants. This studyin vivo digesta kinetic measurements arein vitro gas production from potentially digestible NDF (pdNDF) was measuredkd of pdNDF, estimated bykd and digestibility of pdNDF, estimated by gas production, of ruminalkd forin vitro gaskd estimated by rumen evacuation.