Foram realizadas observações do comportamento apresentado por 16 vacas mestiças, em lactação, durante 72 horas consecutivas interrompidas pelas ordenhas, em pastos de capim fino e de Napier.Os tempos de pastejo obtidos mostraram-se iguais para as duas gramíneas (7 h, 24 mm por período de 24 h) e independentes das produçoes de leite, ocorrendo em sua maior parte (72%) durante o dia (das 5 h as 18 li, 55 mm).O ato de pastejar foi mais intenso: a) entre 8 e 10 h; b) entre 15 e 19 h; c) por volta das 23 h e, logo após, entre 1 e 2 h; d) depois do alvorecer, mas nêste instante os animais foram conduzidos ao estábulo para serem ordenhados. 

Sixteen crossbred cows early in lactation were divided into blocks by production and at random to pastures of Pará grass (Brachiaria mutica) and Elephant grass (Pennisetum purpureum).Observations of their behaviour were conducted for 72 hours, making notations about each animal every 5 minutes. These records were interrupted by milking. Observers were unable to distinguish if animals were ruminating at night, so this data is missing. Because of this, only the grazing times were analized on a 24 hour basis. Such data could be accepted with confidence, and they are the most important.Grazing times for the two grasses were not statistically differents; blocks of cows with different productions were not different, also. The correlation coefficent between grazing times and milk production was r — 0,417, which was not significant at 5% level.About 72% of the grazing time ocurred in the day, as the average for both the grasses, and the total hours of grazing were 7 h, 24 m.The periods of more intense grazing were: a) between 8 and 10 a.m.; b) between 3 and 7 p.m.; c) about 11 p.m. and again between 1 and 2 a.m.; and d) about sunrise, but this latter grazing period was interrupted by morning milking.The cows were lying down and excreted feces and urine more at night; they grazed and drank water more during the day; they walked about and were standing an equal amount of time, day and night.