The objective of this trial was to study the behavior of lactating Holstein cows grazing pasture containing elephantgrass (Pennisetum purpureum Schum.) and a mixture of black oat (Avena strigosa Schreb.) plus ryegrass (Lolium multiflorum Lam.). Data from six early to mid lactating cows were collected every 10 minutes interval by two observers (from 6 p.m. to 6 a.m. and from 8 a.m. to 4 p.m.) at three grazing cycles: 06/17, 08/04, and 09/16 of 2004. The following variables were measured: elephantgrass grazing time, black oat plus ryegrass grazing time, total grazing time (sum of elephantgrass and oat plus ryegrass), rumination time, and idle time. Initial herbage mass, chemical composition of ingested forage, and environmental conditions were also evaluated. Cows spent more time grazing after each milking and decreased thereafter. Diurnal grazing time was longer than nocturnal. Black oat plus ryegrass grazing time was greatest when the percentage of leaf lamina was lowest in the elephantgrass. Idle time decreased and rumination time increased during grazing cycles as a consequence of reduction in the proportion of leaf lamina and elevation on that of stems in the winter species (black oat plus ryegrass). Elephantgrass was grazed at all three grazing cycles. Availability of plant species with different growth cycles allowed animals to select a high quality forage diet.
elephantgrass; ethology; oat; ryegrass
