Eating behavior, ruminal fermentation, and milk production in lactating dairy cows fed rations that varied in dry alfalfa hay and alfalfa silage content

The objective of this experiment was to evaluate effects of various inclusion levels of dry chopped alfalfa hay and alfalfa silage in lactating dairy cow rations on eating behavior, rumen fermentation, milk yield, and components. Eight multiparous Holstein cows (79±11 d in milk initially; 647±36. kg body weight) were randomly assigned to replicated 4×4 Latin squares; one square of rumen canulated animals. During each of the 4 periods, cows were fed 1 of 4 diets that were chemically similar but varied in dry chopped alfalfa hay level. Forage dry matter (DM) consisted of 50% corn silage and 5%, 10%, 20%, or 40% dry chopped alfalfa hay. The remaining forage DM was alfalfa silage (45%, 40%, 30%, and 10% respectively). It was determined that sorting did not change with increasing alfalfa hay content and that dry alfalfa hay can be included in the ration up to 23.5% of ration DM with no negative effects on DM intake, milk yield, and rumen fermentation. Small decreases in milk fat and protein content occurred with increasing dry hay inclusion. Despite changes in total mixed ration refusal particle size distribution throughout the day, by 24. h after feeding, no significant ration sorting occurred when measured either by selection indices or actual consumption of various particle size fractions (>19.0, >8.0, >1.18. mm, and pan). Data from the Penn State and Ro-Tap particle separators produced different particle size distributions from the same sample. This indicates that data obtained from these 2 methods of particle separation are not directly comparable and that the method of particle separation should be considered when interpreting experimental results.