Relationship of bite mass of cattle to sward structure of four temperate grasses in short‐term grazing sessions

The effect of sward structure of four temperate grass species on the bite mass of cattle was evaluated. Micro‐swards (79 cm × 47 cm; approximately the area of a feeding station) of orchardgrass (Dactylis glomerata L.), quackgrass [Elymus repens (L.) Gould], meadow fescue [Schedonorus pratensis (Huds.) P. Beauv] and reed canarygrass (Phalaris arundinacea L.) were offered to Holstein dairy cows in short‐term grazing sessions in 2006 and 2007 using a 4 × 4 Latin square design. Cows were allowed to take fifty bites in each session. Bite mass was calculated by dividing the adjusted change in weight of the micro‐sward by the number of bites. Sward surface height, bulk density and distribution of herbage dry matter (DM) in the canopy were measured pre‐ and post‐grazing. Sward structure differed among the grass species within years but bite mass (on a fresh or DM basis) was not affected. Higher surface heights and bulk densities in 2006 compared with 2007 (averaged across grass species) resulted in greater bite masses of DM in 2006. Values were 25·7 cm vs. 17·0 cm for surface height; 1219 g m^?3 vs. 926 g m^?3 for bulk density; and 1·05 g DM bite^?1 vs. 0·50 g DM bite^?1 for 2006 and 2007 respectively. Within the context of this study, differences between years in bite mass, associated with greater changes in sward structure, were more important than differences among grass species.