Effects of grain supplementation on the intake and digestibility of range diets consumed by goats

Two studies were conducted during the wet and dry seasons to investigate the effects of grain supplementation on intake and digestibility of range diets consumed by goats. Fifty pre-puberal female Moxoto goats were randomly assigned to one of the four dietary treatments: grain supplementation at 0, 0.6, 1.2, and 1.8% BW. Intake and fecal output of OM were determined using Cr2O3 and ADL as internal and external markers, respectively. Diet quality was determined through the collection of extrusa samples using 20 adult esophageally fistulated goats, which were equally and randomly assigned to one of the four dietary treatments. During the dry season, goats selected a diet with more (p < 0.01) protein and less (p < 0.01) cell wall components than during the wet season. An increase in the level of supplement from 0% to 1.8% BW during both these seasons resulted in a decrease in forage of OM intake, and an increase in total OM intake. During the wet season, total OM intake increased from 50.5 to 61.9 g/kg(0.75), or from 2.71 to 3.26% BW. Digestibility of OM also increased from 48.7% to 65.7%. During the dry season, total OM intake increased from 55 to 74 g/kg(0.75) Or from 1.6% to 2.6% BW, and digestibility of OM increased from 47.7% to 66.2%. During the dry season, the inadequacy of 1.6% BW OM intake observed in unsupplemented goats could be attributed to the restriction of free diet selection. Although CP intake of unsupplemented animals was higher than the maintenance requirement, grain supplementation was required to allow for enough digestible OM and CP intakes to meet energy and protein requirements for growth. 1999 Published by Elsevier Science Ireland Ltd.