SOURCES OF VARIATION IN THE GRAZING BEHAVIOR OF DAIRY-COWS

Measurements of grazing, ruminating and idling time and number and dur ation of bouts of these activities were made on cows grazing a perenni al ryegrass-white clover sward on a number of different occasions betw een 8 May and 10 July 1990 at the North Wyke Research Station, Devon, UK. Repeatabilities, calculated using the residual maximum likelihood method, were low for all measurements, the highest being for idling ti me. Coefficients of variation were generally lower between periods tha n between animals for total activity times and ruminating and idling b out duration but were higher for the number of bouts of all activities and for meal duration. Grazing time and meal duration increased signi ficantly as the season progressed, while the number of bouts of all ac tivities declined. Behaviour was not significantly correlated with met eorological conditions. There were no significant correlations between production traits and mean behaviour of cows across periods.