The Effect of Intake Level of a Soy Hull Diet on Digestibility in Ram Lambs and Mature Non-Lactating Ewes
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There is a positive effect of soy hull feed supplementation on production and intake in ruminants. This is due to the high fraction of fermentable neutral detergent fiber (FNDF) found in soy hulls, which is highly digestible by rumen microbes and may optimize VFA production for rumen health. However, high levels of intake of a soy hull diet can decrease digestibility due to an increased rate of passage. In this project, the effect of feeding soy hull-based diets at intake levels of 2, 3, or 4% of body weight was quantified in weanling ram lambs and mature, non-lactating ewes. The apparent dry matter digestibility (DMD) and digestibility of NDF were quantified using a chromium marker which was measured in the feed and feces. In ram lambs, apparent DMD decreased by 8.3 percentage units and digestibility of NDF decreased by 12.1 percentage units for each 1 percentage unit increase in DMI as a percentage of BW (P<0.001). In mature ewes, the depression in digestibility was less pronounced, with DMD decreasing by 2.9 percentage units and digestibility of NDF decreasing by 4.5 percentage units for each 1 percentage unit increase in DMI as a percentage of BW (P = 0.034). These experiments demonstrated a linear decrease in digestibility with increased intake, and the decrease was less severe in sheep being fed at or near their maintenance requirement.
sheep; NDF; fiber; soy hulls; digestibility
dissertation or thesis