Effect of grinding and moisture level of corn grain on performance of lactating dairy cow

High producing dairy cows require large amounts of energy, thus dairy diets often contain large quantities of grain. Most of the energy in grain is in the form of starch. Any process that disrupts the physical structure of grain is likely to impact on starch utilization, because starch becomes exposed to the rumen microbial population. Grinding is a simple method for disrupting physical structure of grain. Increasing grain moisture content is another approach to altering physical structure because water molecules can reduce intermolecular interactions and increase starch availability. Therefore, two experiments were conducted to evaluate the effect of grinding and moisture level of corn grain on performance of lactating dairy cows. The first experiment was a simulation of a grazing situation in which cows were fed with fresh chopped forage and a constant amount of supplemented concentrate containing either finely ground dry shelled corn, coarsely ground high moisture ear corn or finely ground high moisture ear corn. Milk production and milk composition were not altered by varying the source of corn, however nitrogen and starch utilization were improved by fine grinding of corn. In a second experiment, cows were fed a total mixed ration containing either dry shelled corn, high moisture ear corn or high moisture shelled corn. Each corn treatment was either coarsely or finely ground. In addition to this, cows were divided into two groups and were fed once or twice daily. In the once daily feeding, no difference in milk yield and milk composition were obtained by varying the type of corn, however, when cows were fed twice daily, increasing moisture level of corn and fine grinding increased milk production. Starch utilization was increased more by fine grinding than by increasing moisture level of the grain, suggesting that an increase in the available surface area for microbial attachment to the grain may be a more important factor for increasing starch utilization and for increasing milk production than is feeding high moisture feeds. Feeding twice daily rather than once daily increased milk production by about 5%.