Digestion of alfalfa and grass silages in sheep. 1. Rates of fermentation in and passage from the reticulorumen.

Abstract

Wilted lucerne and grass silages were given for 9 weeks (3 weeks adaptation, 6 weeks experimental) to mature wethers. Fractional rate of passage of particles (k_p) from the reticulorumen, as determined with chromium-mordanted neutral detergent fibre (Cr-NDF), was negatively related to digestibility, but positively to feed intake. Ratio of k_p to k_l (liquids) decreased with higher intake of indigestible material. Models were developed to interrelate cell wall pool in the reticulorumen, passage of undegraded cell walls in the proximal duodenum, fractional rate of passage of particles, fractional rate of degradation of cell walls (k_d), and the proportion of large particles (f_L) within the total particle pool in the reticulorumen. Although estimates of k_d and f_L were not very accurate yet, differences between silages could be characterized. The k_d values of cell walls in grass silages were negatively related and f_L positively related to stage of maturity at harvesting. For silages with similar k_d, the extent to which cell walls left the reticulorumen was higher with lucerne than with grass silage. (Abstract retrieved from CAB Abstracts by CABI’s permission)