Intake and Digestibility of Alfalfa-Tall Fescue Combination Diets Fed to Lambs

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Abstract
An in vitro experiment and two lamb digestion trials were conducted to evaluate intake and digestibility and possible associative effects of various combinations of alfalfa and fescue hay. Lambs were fed fescue hay diets with alfalfa replacing fescue at 0, 25, 50, 75 and 100% of the diet. The same forage combinations were evaluated in the in vitro experiment. A quadratic response (P<.01) to level of alfalfa was observed for in vitro dry matter (DM) and neutral detergent fiber (NDF) disappearance, with the forage combination containing 25% alfalfa having greater in vitro disappearance of DM and NDF compared with the 0 and 100% alfalfa diets. A linear increase (P<.01) in the rate of in vitro DM disappearance was measured (3.6, 4, 5, 5.1 and 6.1%/h for 0, 25, 50, 75 and 100% alfalfa substrates, respectively), but level of alfalfa had no effect (P>.10) on rate of NDF digestion. For the digestion trials, DM intake increased linearly (P<.01) with increasing levels of alfalfa in the diets; however, a quadratic relationship (P<.08) indicating a positive associative effect was observed for DM and NDF digestibility when lambs were fed ad libitum. When lambs were restricted to 450 g of DM intake daily, a linear increase (P<.05) in DM and linear decrease (P<.01) in NDF digestibility was observed with increasing levels of alfalfa addition. Results of this study demonstrate positive associative effects for the digestibility of alfalfa-fescue combination diets with ad libitum intake and a positive linear relationship between level of dietary alfalfa and diet DM consumption. Copyright © 1985. American Society of Animal Science . Copyright 1985 by American Society of Animal Science

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