Chewing activity and digestive responses of cows fed alfalfa forages.

Nonlactating Guernsey cows were fed alfalfa silage or coarsely chopped, coarsely chopped and reconstituted, or long alfalfa hays. A computer system was developed to monitor chewing activity. Effects of diets upon chewing activity, digestibility, and ruminal parameters were determined. Digestibilities of DM and N were lower for silage than for hays. Cows fed silage had lower ruminal ammonia concentrations that were caused, at least in part, by greater bound N. Digestibilities of DM, N, and fiber were not different among the hays. The computer system recorded 98% of chews; visual measurements of chewing activity agreed well with computer-logged data. Cows spent more time (463 vs. 348 min/d) eating long alfalfa hay than silage; time spent ruminating, total chewing time, and chewing rates were not different among diets. During eating, cows fed hay had more chews per unit of DM or NDF than when eating silage; during rumination, diets had no effect. Eating time of cows fed alfalfa silage was less than for those fed alfalfa hay. Coarsely chopped alfalfa hay was as effective as long alfalfa hay in eliciting chewing activity.