Eating and ruminating activities of cattle fed alfalfa or orchard-grass harvested at two stages of maturity

Abstract

Four Hereford heifers (mean weight, 371 kg; SD, 17) were fitted with esophageal fistulae and used in an experiment designed as a 4 × 4 Latin square to determine the effects of species and stage of maturity of forage on eating and ruminating activities. Heifers consumed an average of 5.45 kg d−1 of DM from (1) alfalfa, 10% bloom (21% CP, 37% NDF); (2) alfalfa, 50% bloom (16% CP, 47% NDF); (3) orchardgrass, anthesis (17% CP, 56% NDF); and (4) orchardgrass, post-anthesis (14% CP, 59% NDF). Time spent eating was similar for all forages (360 min d−1; P > 0.05). This resulted in alfalfa NDF being subjected to more chewing (167.8 vs. 112.2 min kg NDF−1; P = 0.001). More DM was solubilized during eating from alfalfa than from orchardgrass (38.1 vs. 27.0%; P = 0.001), but less saliva was added per gram of DM (1.94 vs. 3.09 g; P = 0.001). Advanced stage of maturity of both forage species decreased solubilization of DM (28.1 vs. 37.0%; P = 0.002) and increased saliva added per gram of DM (2.28 vs. 2.74 g; P = 0.001) during eating. Rumination time was similar (312 min d−1; P > 0.05) for animals fed alfalfa and orchardgrass. Consequently, rumination chewing per kilogram of alfalfa NDF was greater (140.8 vs. 98.3 min; P < 0.01). More time was spent ruminating late- vs. early-cut forage (348 vs. 276 min d−1; P = 0.04). Results indicate that characteristics of grass and legume hays harvested at similar physiological stages of maturity have little effect on chewing behavior of cattle fed restricted amounts of DM. Despite similar times spent eating and ruminating, the effects of chewing vary with species of forage and stage of maturity. Key words: Cattle, mastication, rumination, forage quality