Factors Affecting Grazing and Rumination Behaviours of Dairy Cows in a Pasture-Based System in New Zealand

Simple Summary Understanding the trends in grazing and rumination behaviours and their variation can provide farmers with information about the health status, physiological state, productivity, and welfare of the animal. Considering this, we studied variations in grazing and rumination times in grazing dairy cows due to breed, lactation year, breeding worth, days in milk of the individual cow, and season and supplementary feeds. AfiCollar device was used to monitor and record the behaviours of grazing cows affiliated with Holstein-Friesian, Jersey, and KiwiCross breeds in different years of lactation during different seasons over three years. We found grazing time and rumination time varied among the individual cows, during different seasons (or stages of lactation), and when cows were fed with different supplements. Jersey cows, and in general, the cows in the first year of lactation relatively grazed for a longer period. Grazing time and rumination time were longer at the start of lactation in spring and shorter at the end of lactation in autumn. These findings could contribute to improving the measures for pasture management, and additional feed supply for a mixed herd comprising Jersey, Holstein-Friesian and KiwiCross breeds in different years of lactation during different seasons over the lactation period. Abstract This study investigated the variation in daily time spent grazing and rumination in spring-calved grazing dairy cows (n = 162) of three breeds, Holstein-Friesian (HFR), Jersey (JE), and KiwiCross (KC) with different breeding worth index, and in different years of lactation (1st, 2nd, 3rd, 4th). The cows were managed through a rotational grazing system and milked once a day at 05:00 a.m. The cows grazed mainly pasture and received supplementary feeds depending on the season. Automated AfiCollar device continuously monitored and recorded grazing time and rumination time of the individual cows throughout the lactation period for three study years (Year-1, Year-2, Year-3) with 54 cows per year. A general linear mixed model fitted with breed × lactation year with days in milk (DIM), breeding worth (BW) index value, individual cow, season, and feed, and their interactions was performed in SAS. Variance partitioning was used to quantify the effect size of study factors and their interactions. Individual cows, DIM, and BW (except Year-3) had effects on grazing and rumination times throughout the study years. Grazing time and rumination time were different for different seasons due to varying supplementary feeds. Grazing time varied among breeds in Year-2 and Year-3, and among lactation years only in Year-1. Although rumination time differed among breeds in Year-3, it remained the same within different lactation years. Grazing time and rumination time had a negative relationship with each other, and their regression lines varied for different seasons. The total variance explained by the model in grazing time was 36–39%, mainly contributed by the individual cow (12–20%), season (5–12%), supplementary feed (2–6%), breed (1–5%), and lactation year (1–6%). The total variance explained in rumination was 40–41%, mainly contributed by the individual cow (16–24%), season (2–17%), supplementary feed (1–2%), breed (2–8%), and lactation year (~1%). These findings could contribute to improving the measures for feed resource management during different seasons over the lactation period for a mixed herd comprising JE, HFR and KC breeds in different years of lactation.