Performance of Lambs on Perennial Ryegrass, Smooth Bromegrass, Orchardgrass and Tall Fescue Pasture I. Live Weight Changes, Digestibility and Intake of Herbage2

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Abstract
Grazing and feeding trials were conducted in 2 years to determine changes in live weight, digestibility and intake of herbage by early-weaned lambs on four perennial grasses. Live weight gains of lambs over the grazing season on tall fescue pasture were not different from those on perennial ryegrass, but were lower than those on smooth bromegrass and orchard-grass. In feeding trials with cut herbage, dry matter digestibility (DMD) of tall fescue at an early growth stage was lower than that of other species, although this was not the case for more mature forage. Levels of intake followed trends in DMD. The correlation coefficient relating intake to DMD was .39. Intake and DMD were calculated by fecal index techniques for grazing lambs at four periods from April to October in each year. Regressions of fecal nitrogen on DMD differed with grass species, but not with year. The quality of perennial ryegrass declined rapidly between spring and summer periods, while DMD and intake of tall fescue by lambs on fall regrowth herbage were lower than for the other perennial species. On a seasonal basis, rates of gain and body weights of lambs grazing different grasses related fairly consistently to estimates of digestible dry matter intake. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.

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