Journal of Animal Science, Vol 72, Issue 9 2455-2463, Copyright © 1994 by American Society of Animal Science

JOURNAL ARTICLE

Influence of moisture content of forage diets on intake and digestion by sheep

T. N. Pasha, E. C. Prigge, R. W. Russell and W. B. Bryan
Division of Animal and Veterinary Science, West Virginia University, Morgantown 26505-6108.

To determine the effect of forage moisture content on intake and digestion kinetics in sheep, a metabolism trial was conducted using 16 mature wethers (44 kg BW) in a completely randomized design. Forage was harvested at two maturities in early spring from a naturalized pasture composed of temperate grass and legume species. Herbage was harvested at either 8 (early) or 16 cm (late) in height and fed after freezing (high-moisture) or as a dried hay. Intakes of DM (grams/[kilogram BW.75.day]), NDF, ADF, and CP (grams/day) (P < .05) and coefficients for DM, NDF, and ADF digestibilities were greater (P < .01) for hay than for high-moisture forage. Mean particulate retention times (MRT) were shorter (P < .05) for high-moisture forage (23.3 h) than for hay (30.7 h) diets. Early-harvested forages had shorter (P < .05) MRT values (23.9 h) than late-cut forages (30.1 h). Fractional passage rates of 1-mm nylon particles of specific gravity (SG) .90, 1.14, and 1.32 through the alimentary tract were influenced by moisture content of the forage (P < .10) and were faster for frozen forages and increased (P < .01) with an increase in SG. Nitrogen retention was greater (P < .01) for the hay than for the high-moisture forage. In situ DM digestion rates, determined using four ruminally fistulated wethers, showed no differences (P = .67) among forages. The results of this study indicate that differences in digestibilities between hays and high-moisture forages are most likely due to differences in digesta passage rates.