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.