Effect of coarse or fine grinding on utilization of dry or ensiled corn bylactating dairy cows

This study evaluated the effect of coarse or fine grinding of three forms o f corn on the performance of lactating cows. Six diets, fed as total mixed rations, were identical except for the corn portion of the diet. Corn treat ments were dry shelled corn, high moisture ensiled ear corn, and high moist ure ensiled shelled corn, either coarsely or finely ground. The experimenta l design was a 6 x 6 Latin square with 36 cows. Eighteen cows were assigned to the six different treatments and were fed once daily. Within this group of 18 cows, six had a ruminal cannula and were used to evaluate nutrient d igestibilities and ruminal fermentation. The remaining 18 cows, six of whic h were ruminally cannulated, were similarly assigned, except they were fed twice daily. In the group fed once daily, milk production and composition w ere not affected by treatment. Starch digestibility was greater with the hi gh moisture and with the finely ground corn treatments. In addition, the hi gh moisture ensiled corn treatments had reduced ruminal ammonia concentrati ons. In the group that was fed twice daily, milk production and protein yie ld were greatest for the finely ground high moisture ensiled shelled corn t reatment. Starch utilization was improved by fine grinding. Lower ruminal a mmonia concentrations were obtained with the high moisture ensiled corn tre atments, and there was a tendency for reduced ammonia concentration with fi ne grinding. Results indicate that high moisture ensiled corn as well as fi ne grinding improved nitrogen and starch utilization.