Effect of grinding of maize and level of starch on digestibility and performance of Saanen goats

The purpose of this experiment was to evaluate the effects on intake, digestibility and lactational performance of goats when fed diets containing whole or ground maize grain at two different dietary starch levels through substitution of beet pulp for maize. Eight second parity Saanen goats in mid lactation were used in a digestibility trial. The experimental design was a duplicated 4x4 Latin square with a 2x2 factorial arrangement of treatments. The goats were fed four diets, with a forage:concentrate ratio of 40:60, containing: 33.5% (on dry matter basis) whole maize grain or 33.5% ground maize grain in the diets with high starch content; 22.5% dried beet pulp and 11.0% whole maize grain or 11.0% ground maize grain in the two diets with low starch content. The high starch diets significantly decreased DMI in comparison with the low starch diets (2333 and 2229 g/d, for low and high starch diets, respectively). Substitution of beet pulp for maize significantly improved NDF and ADF digestibility (56.4 and 55.5% and 42.2 and 38.9%, for low and high starch diets, respectively) due to the lower content of starch. Starch digestibility was influenced by the grinding of maize: whole grain (92.6%) was less utilized than ground grain (97.7%), despite not impairing total DM digestibility. The ground maize grain depressed feed intake and milk yield in the high starch content diets. The data obtained suggest that the grinding of maize is not likely to be worthwhile for lactating goats.