Grazing behaviour of dairy cows fed different levels of concentrates

Understanding how dairy cows adjust their grazing behaviour and associated pasture intakes in response to concentrate feeding may be important in developing strategies that optimise profit from concentrate feeding in pasture based dairy herds. The aim of this study was to offer different levels of concentrates and by using GPS collars and motion sensors, capture and record grazing behaviour of individual cows. This study was conducted on 24 Holstein-Friesian multiparous cows selected from the Tasmanian Institute of Agriculture Dairy Research Facility at Elliott, Tasmania. Two groups consisting of 12 cows each were established and balanced for milk production, days in milk, body weight and age. Each group of cows was allocated to one of two concentrate feeding levels. Cows received 50% of their concentrate feed allocation of 6.0 or 0.0 kg DM/day twice daily during milking via automatic feeders. Cows were grazed as one herd on predominantly perennial ryegrass pastures with a daily forage allocation allowance of approximately 30kg DM/cow/day of feed on offer above ground. Collars with GPS, 3-axis accelerometer and 3-axis magnetometers were fitted to each of the cows. There was a significant (P < 0.05) difference in the proportion of time spent grazing between the two grain feeding groups, with cows receiving 0kg of concentrate spending a larger proportion of time grazing than cows receiving 6kg. There was also a significant (P < 0.05) interaction between time of day (hour of day) and concentrate feeding group, with cows receiving 6kg concentrate spending less time grazing compared with the cows receiving 0kg concentrates following the morning milking but not for the period following afternoon milking. This indicates different factors may regulate grazing behaviour at differing times of the day.