Mastication and rumination in relation to body size of cattle

Effect of body size on number of minutes per kilogram cell wall constituents spent chewing during eating and ruminating was studied in a total of 59 mature animals including 18 Holstein cows, 12 Jersey cows, 6 Ayrshire cows, 11 Guernsey cows, and 12 steers. Larger animals were more efficient chewers, spending less time chewing per kilogram of ingested cell wall constituents. Body size accounted for 52% and differences of intake of cell wall constituents accounted for an additional 22% of variability of chewing time. Neither breed nor ambient temperature contributed significantly to explaining the variability. Size of fecal particles and amount of each size did not differ significantly for different body sizes. These results suggest that acceptability of particles to the reticulo-omasal orifice was not different for different body sizes. Correlation was nil between body size and speed of chewing.