Effect of TMR physical form on nutritional behavior and nutrient digestibility in lactating dairy cows

This experiment was carried out to evaluate nutritional behavior and nutrient digestibility in lactating dairy cows. Three Brown Swiss dairy cows (average milk yield of 22 kg/d and 200±20 days in milk) were used in a latin square design (3×3) for a three periods. The experimental treatments were 1. TMR with mash concentrate, 2. TMR with pellet concentrate and 3. TMR in a cubic form. Diets chemical composition were similar but were  were different physically.  The experimental diets were delivered to the animals twice daily at 0800 and 2000. Each experimental period consisted of 21 days; 14 days for adaptation period and 7 days for sampling. The results indicated that average length of eating, rumination and chewing total over 24 hours, and per 1kg consumed NDF and dry mater intake was significantly lower (P<0.05) for cows fed with cube diet. However, it was not significant between mash and pellet diets.. Total apparent digestibility was not significantly affected by the experimental diets. Therefore, Dry matter intake was higher in TMR with pellet concentrate and on 2h after feeding ( for mash,pellet and cube diets were:5.03,7.82 and 5.03 kg resoectively). Plasma glucose and urea nitrogen increased as significant (P<0.05) in diet with pellet concentrate. It seems that decreasing feed particle size in cubic diet decreased chewing activity. It is concluded, when particle size increased, chewing activity increased but no effect on digestibility of DM, OM,CP and NDF.