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Three experiments investigated how forages of different chemical composition affect rumination time of cattle. Three single reversal designs used four dairy heifers and two dairy steers in Experiment I and four dairy heifers in Experiments II and III. The rumination time produced by feeding a single 5-kg meal of test forage was measured with jaw motion recordings. In Experiment I the test meal was fed after 2 days of fasting; following the test meal no more was offered for an additional 2 days. In Experiments II and III only alfalfa pellets were offered during the 2 days before and after the test meal, at the rate of 2.27 kg per head per day. In Experiment I the animals which were fed straw ruminated 578 minutes following the test meal; the animals fed an excellent quality hay ruminated a shorter (P < .05) time of 369 minutes. Experiment II compared a good-quality mixed second-cutting hay with straw. The straw produced 539 minutes’ rumination time, and the second-cutting hay produced a shorter (P < .05) time of 387 minutes. In Experiment III good-quality orchardgrass produced 258 minutes’ rumination time; poor-quality orchardgrass produced a longer (P < .05) time of 449 minutes. The correlation between rumination time and cell wall constituent (CWC) content was 0.94.
Welch et al. (Mon,) studied this question.