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EFFECT OF MEADOW HAY QUALITY ON VOLUNTARY INTAKE, RATE OF PASSAGE AND RATE OF STRUCTURAL DEGRADATION IN GROWING CATTLE
Abstract
Initial growth of a mixed of cool- and warm-season species was harvested as hay at three times during the growing season from a subirrigated Nebraska Sandhills meadow. The hay was fed ad libitum to rumen fistulated steers for evaluation of: (1) voluntary intake; (2) rate of passage, retention time and ruminal pool sizes of different size particles estimated by fecal excretion of ruminally administered markers; (3) rates of particle degradation and passage estimated by rumen concentrations of ruminally administered markers and (4) in vitro analysis of hay nutrient content and digestibility. Forage quality estimated by digestible organic matter intake decreased (P < .01) from hay 1 to hay 2 or 3. Average daily gain (ADG) was highest (P < .04) for steers fed hay 1, there were no differences (P > .1) for the later two harvests. Rate of passage estimated by fecal excretion decreased (P < .10) with increasing forage maturity. Passage rates estimated by a two compartmental fecal model were numerically lower than those estimated by a one compartmental model but were numerically higher than those estimated by a peak decay model. Pool sizes of the three particle size groups increased (P < .09) from hay 1 to 3. Pool sizes estimated by a one compartmental fecal model tended to be larger than the same pools estimated by a two compartmental model. Retention times were less (P < .03) for hay 1 than for hay 2 or 3. Retention times estimated by a two compartmental model were approximately 50% longer than those estimated by a one compartmental model. A three pool rumen model was used for the estimation of particle degradation and passage from the rumen. There were no differences (P > .10) in particle disappearance from either the 1680 or the 1680/850 particle pools for the three hays. However, hay 2 had faster (P < .006) rate of degradation from the 1680 to the 1680/850 particle pools and slower (P < .05) rate of degradation from the 1680/850 to the 850 particle pools than the other hays. Rate of passage from the 850 particle pool decreased (P < .002) from hay 1 to 3. Rate of passage for the 1680/850 particles was lowest (P < .006) for hay 3. The model used for the estimation of particle degradation and passage appears to have merit, however, further refinement by including the digestibility of the different particle fractions appears desirable.
Subject Area
Livestock
Recommended Citation
WORRELL, MICHAEL A, "EFFECT OF MEADOW HAY QUALITY ON VOLUNTARY INTAKE, RATE OF PASSAGE AND RATE OF STRUCTURAL DEGRADATION IN GROWING CATTLE" (1985). ETD collection for University of Nebraska-Lincoln. AAI8521488.
https://digitalcommons.unl.edu/dissertations/AAI8521488