Effect of Diet on In Vitro and In Vivo Rumen Lactate Disappearance Rate in Sheep2

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Abstract
Four fistulated sheep were fed either chopped grass hay, hay plus two levels of lactic acid or a corn based concentrate diet in a 4 x 4 extra-period latin square design with 21 day experimental periods. Disappearance rates of infused lactic acid in an in vitro fermentation were measured on day 7, 11, 14 and 21 of each period. On day 15 of each period, lactate was infused into the rumen of sheep to measure in vivo disappearance rates. Both in vitro and in vivo disappearance rates were lower by at least 50% when the hay diet was fed compared to the hay plus lactic acid and concentrate diets. The in vitro disappearance rates of lactate in ruminal fluid from sheep fed hay, hay plus lactic acid (two levels) and concentrate were 19, 44, 57 and 127 mg/100 ml/hr, respectively, on the 21st day. In contrast, the in vivo lactate disappearance rates were 154, 486, 500 and 313 mg/100 ml/hr, respectively. The use of whole instead of strained ruminal contents as inocula resulted in in vitro treatment rankings similar to those obtained in vivo. Copyright © 1976. American Society of Animal Science . Copyright 1976 by American Society of Animal Science.