Variations in the 24-hour temporal patterns and time budgets of grazing, rumination, and idling behaviors in grazing dairy cows in a New Zealand system.

This study investigated the variations in the temporal distributions and the lengths of times utilized for grazing, ruminating, and idling behaviors by grazing dairy cows over 24 hours. Spring-calved lactating dairy cows (n = 54) from three breeds, Holstein-Friesian (HFR), Jersey (JE), and KiwiCross (KC) in different lactations (1 st, 2 nd, 3 rd) and with different breeding worth index values (103<BW>151) were selected. The cows were managed through a rotational grazing scheme and milked once a day at 5:00 hrs. The cows grazed mainly pasture and consumed additional feeds (maize silage and turnips) in the summer and autumn seasons. AfiCollar was used to recorded grazing and rumination behaviors (min/h) by the individual cows throughout the lactation period (~270 days). The time (min/h) neither utilized for grazing nor rumination was counted as idling behavior. A repeat measure design with PROC MIXED was performed in SAS considering the effects of breed, lactation, individual cow, the hour of the day, season, day within the season, and supplementary feed within the season to evaluate the difference in grazing, rumination, and idling behaviors. Hour of the day, season, day within season, and supplementary feed had significant effects on grazing, rumination, and idling behaviors. Regardless of the season and supplementary feed, cows spent most of the daytime grazing and most of the night-time ruminating. Grazing activity remained consistently high throughout the day with two peaks around dawn and dusk and a short peak around midnight. Rumination activity remained high from the late evening until early morning. Grazing and ruminating patterns were similar between different breeds and lactations, however, JE cows grazed slightly longer than HFR and KC, and first-lactation cows also grazed slightly longer than those in higher lactations. The onset and cessation of grazing by the cows were adjusted according to varying day lengths by season. Cows finished grazing earlier when they consumed additional supplements or silage along with pasture. Cows from different breed groups and lactations spent most of their 24 hours grazing followed by ruminating and idling. Season and supplementary feed potentially caused variations in behavior time budgets. These findings should support improving measures for grazing management to address pasture and additional feed demands, and animal welfare in varying environmental and/or managemental conditions.