Physically effectiveness of beet pulp-based diets in dairy cows as assessed by responses of feed intake, digestibility, chewing activity and milk production.

摘要

Nine multiparous Holstein cows (DIM=56+or-5 day) were randomly assigned to three experimental diets containing fine-dried (T1), normal-dried (T2) and pelleted (T3) beet pulp (BP) at 12% on a dry matter basis in a 3x3 change over design in three 21 day periods to evaluate the effects of three types of BP. Bulk density, functional specific gravity and water-holding capacity of ration and intake were similar, but intake of physically effective fibre was different among treatments. Without significant differences, nutrients' digestibility in T1 trended to be higher than T2 and T3. Ruminal liquid pH and N-NH3 concentration were lower in T1 and higher in T3 than T2. Grinding and pelleting of BP increased and decreased volatile fatty acid concentration respectively. Grinding decreased acetate and propionate and increased butyrate and lactic acid. In contrary to pelleting, grinding of BP increased the particulate ruminal passage rate, but decreased ruminal mean retention time and lower compartment mean retention time. Pelleting of BP decreased ruminal passage rate, but increased ruminal mean retention time and lower compartment mean retention time. Grinding increased 5.64, 5.9 and 5.8% eating time, rumination and total chewing activity in comparison with normal BP respectively. Pelleting increased 2.7%, 16.3% and 10.0% eating time, rumination and total chewing activity in comparison with T2 respectively. Milk yield had no significant difference, but milk yield adjusted to 4% fat, and milk fat (kg/day), fat, protein, casein and total solid of milk (%) were affected by the treatments. Results from this experiment show that based on milk fat assay, grinding did not reduce effectiveness of BP, but pelleting significantly increased effectiveness of BP. In addition, based on total chewing activity, grinding did not reduce physically effectiveness of BP, but pelleting of BP increased its physically effectiveness.