Effects of pellet size and inclusion of binding agents on ruminal fermentation and total-tract digestibility of beef heifers, and cow performance under winter grazing conditions

Abstract

Objective: The objective of this research was to evaluate the effect of pellet size and the inclusion of binders to increase pellet durability on ruminal fermentation and total-tract digestibility, and pellet utilization when grazing. Materials and Methods: In study 1, 8 ruminally cannulated heifers were used in a replicated 4 × 4 Latin square design. Heifers were fed a grass-hay-based diet supplemented with small (SP; 3.96-mm diameter) or large pellets (LP; 12-mm diameter) that either included (B+) or did not include binders (B−). In study 2, groups of 5 cows grazing straw–chaff in paddocks (n = 4) during winter were supplemented with SP, SP-B+, or LP-B+. Results and Discussion: In study 1, pellet size and binder inclusion did not affect (P > 0.10) forage intake, pellet intake, or ruminal pH (P > 0.10). Heifers fed LP-B+ had a greater proportion of acetate than heifers fed the SP-B+ (size × binder; P = 0.01), and heifers fed LP-B− had a greater proportion of propionate than did those fed LP-B+ (size × binder; P = 0.03). The molar proportion of butyrate was greater for heifers fed B+ compared with B− (binder, P = 0.05). Apparent total-tract digestibility was not affected (P > 0.10). In study 2, differences were not observed among treatments (P > 0.10). Implications and Applications: These data indicate that pellet size and binder inclusion do not affect forage or pellet intake, apparent total-tract digestibility, or cow performance. However, pellet size and binder inclusion may modulate ruminal fermentation.