Abstract

Passage, comminution and digestion rates of large and small particles were estimated using a rumen evacuation technique and total faecal collection with five lactating dairy cows in a 5 x 5 Latin square experiment. Two grass and two red clover silages harvested at early and late primary growth stages and a 1:1 mixture of late harvest grass and early harvest red clover were the dietary treatments. Cows received 9.0 kg supplementary concentrate per day. Ruminal contents and faeces were divided into large (>1.25 mm) and small (1.25-0.038 mm) particles by wet sieving. Indigestible neutral detergent fibre (iNDF) was determined by 12 days ruminal in situ incubation followed by neutral detergent extraction. Plant species did not affect ruminal particle size distribution, whereas advancing forage maturity decreased the proportion of large particles for both grass and red clover silage diets. Ruminal pool size of iNDF was higher (P<0.001) with red clover compared to grass silage diets. Ruminal passage rates of iNDF and potentially digestible NDF (pdNDF) increased with decreasing particle size (P<0.01). Passage rate of iNDF for small particles was slower (P<0.01) when red clover compared to grass silage diets were fed. Particle comminution rate in the rumen was slower (P<0.001) with red clover compared to grass silage diets and it increased (P<0.01) with advancing forage maturity. The contribution of particle comminution to ruminal mean retention time of iNDF in the ruminal large particle pool was smaller (P<0.01) in red clover compared to grass silage diets and it increased (P<0.05) with the mixed silage compared to the separate silages. Passage rate of pdNDF for both large and small particles was not affected by dietary treatments. Digestion rate of pdNDF for large particles was faster (P<0.001) with red clover compared to grass silage diets. Differences in ruminal passage and digestion rates of the large and small particles, in addition to differences in the passage and digestion rates of red clover compared to grass silage diets, emphasize the need to consider particle size and forage type in metabolic models predicting feed intake and fibre digestibility in ruminants. (C) 2009 Elsevier B.V. All rights reserved.

Keywords

Steady-state model; Indigestible NDF; Passage rate; Particle comminution rate; Digestion rate; Red clover; Grass

Published in

Animal Feed Science and Technology
2010, Volume: 155, number: 2-4, pages: 86-98
Publisher: ELSEVIER SCIENCE BV

SLU Authors

• Huhtanen, Pekka

  • Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Animal and Dairy Science
Veterinary Science


Publication identifier

DOI: https://doi.org/10.1016/j.anifeedsci.2009.10.005

Permanent link to this page (URI)

https://res.slu.se/id/publ/48534