Comparative Energy Availability for Lambs of Four Timothy Varieties at Progressive Growth Stages

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Abstract
Four varieties of timothy, S-50 (Phleumnodosum) and Climax, Drummond and Quebec Common (Phleum pratense), were harvested at successive growth stages in 1962 and the latter three again in 1963 from the same swards, and assayed for digestibility, voluntary dry matter intake (DMI) and digestible energy intake (DEI). Quebec Common reached full bloom the earliest followed by Climax, Drummond and S-50. Seasonal digestibilities declined from an early vegetative stage through full bloom in a uniform manner for all varieties. The rate of daily decline was not merely a function of time, but differed between seasons (0.46 to 0.55% and 0.35 to 0.44% for 1962 and 1963, respectively) and was apparently affected by growing conditions. Differences in varietal digestibilities were minor and inconsistent between years. The seasonal DMI of Climax, Drummond and Quebec Common declined with advancing maturity; that of S-50 did not. During 1962 rates of DMI decline were variable, although an overall reduction in intake was evident for three of the varieties. The DMI of Quebec Common was below the others early in the season, but did not differ from Drummond and Climax late in the season. In contrast DMI of S-50 equalled Drummond and Climax at early growth stages but was much higher late in the season. In 1963 the rate of decline was very uniform, and no consistent differences in DMI were noted. Daily DEI (kcal./Wkg.0.75) combined digestibility and intake factors into a single index similar to the nutritive value index (NVI). Use of both indexes resulted in small but inconsistent varietal differences the first year and no varietal differences the second year. DEI is a more direct and simpler index than the NVI. Digestible dry matter (DDM) yields in 1963 reached nearly identical maximum values at the early heading growth stage. Subsequent growth of Quebec Common and Climax was more than offset by the decline in digestibility, so DDM yields after head emergence dropped sharply for the former and to a lesser extent for the latter. Posthead emergence growth, for Drummond was sufficient to hold DDM yields constant from head emergence to after bloom. Copyright © 1966. American Society of Animal Science . Copyright 1966 by American Society of Animal Science

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