Digestibilities and Nutrient Intakes by Sheep Fed Mixtures of Soybean Stover and Alfalfa

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Abstract
An in vivo experiment consisting of four replications in a 4 × 4 Latin square design involving 16 mature sheep and an in vitro experiment consisting of three replications in a 4 × 4 factorial randomized block design were conducted to evaluate digestibilities and nutrient intakes of mechanically blended mixtures of soybean stover (SBS) and alfalfa (ALF). Associative effects between forage components and chemically isolated cell wall constitutents (CWC) were also determined. Sheep were fed diets composed of only SBS, 2 parts SBS to 1 part ALF, 1 part SBS to 2 parts ALF or entirely of ALF. The same diets were also subjected to in vitro fermentation and correlations between in vivo and in vitro measurements were determined. Intakes of dry matter (DM) and cell wall carbohydrates increased as percentage of ALF increased in the blends. DM intakes were 53.9, 69.8, 100.9 and 106.2 g-(kg BW.75)−1. d−1 with SBS, 2 SBS to 1 ALF, 1 SBS to 2 ALF and ALF, respectively. Increases in the intake of cell wall carbohydrates were generally due to higher total DM intake. Digestibilities of DM and CWC were also increased both in vivo and in vitro as the percentage of ALF increased in the blends. In vivo DM digestibilities were 40.1, 44.9, 52.3 and 58.1% with SBS, 2 SBS to 1 ALF, 1 SBS to 2 ALF and ALF, respectively. Positive and negative associative effects in intake and digestibility were observed when low and high quality forages were blended and used as the sole source of nutrients. SBS at levels greater than 40% of an all forage diet induced negative associative effects when fed to sheep. High positive correlations were observed between in vivo DM digestibility and in vitro DM digestibility and between DM intake and in vivo DM digestibility. Negative correlations were found between in vivo DM digestibility and lignin or insoluble ash content of forages. Copyright © 1982. American Society of Animal Science . Copyright 1982 by American Society of Animal Science.

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