Effects of different systems of feeding supplements on time budgets of cows grazing restricted pasture allowances

Abstract

Farm systems that use a feed-pad for delivering mixed-rations to dairy cows are becoming more common in countries with primarily pasture-based dairy systems, such as Australia. However, feeding a ration on a feed-pad may alter cows’ key daily behaviours such as grazing, ruminating and resting, due to extended time off-pasture. The objective of this study was to compare the time budget of multiparous grazing cows fed partial mixed-rations (PMR) on a feed-pad with that of cows fed supplements during milking and in the paddock (Control). A total of 16 groups of early-lactation, Holstein-Friesian dairy cows consisting of eight cows per group were randomly assigned to each of two dietary treatments (Control and PMR). Control cows were supplemented with wheat grain during milking and grass silage in the paddock, whereas PMR cows received supplements as a mixed-ration on the feed-pad for 80±25min/day after milking. Both diets were isoenergetic and equivalent in dry matter (DM) amounts. Within each feeding system, two groups were randomly assigned to one of the four amounts of supplement (8, 10, 12, 14kg DM/cow/day). Thus, the experiment comprised two main treatments twice replicated and four amounts of supplement in each replicate. Following a 14-day adaptation period, data were collected for 18 days. The posture (lying/standing) and eating behaviour (grazing/ruminating/idling) of each cow was recorded every 10min for 24h over 4 days. Concurrently, IceTag™ activity monitors were used to measure the number and duration of lying bouts. There was no effect of feeding system or amount of supplement on daily lying time (PMR=10.6, Control=10.4h; P>0.05) and number of lying bouts per day (PMR=9.3, Control=9.4h; P>0.05). Daily grazing time was lower in PMR cows than Control cows (PMR=5.2, Control=4.0h; P<0.05) and declined with increasing level of supplement. Ruminating time was not affected by ration but increased with increasing amount of supplement (7.9, 8.7, 8.9, 8.9h respectively; P<0.05). The time interval between the arrival on pasture after milking and the first lying bout was longer in Control cows (PMR=1.3, Control=2.0h; P<0.05), and was significantly longer after morning milking across both treatments. Integrating grazed pasture with supplements fed as a PMR on a feed-pad for approximately 1.5h a day slightly changed the time budget of pasture-based dairy cows with no indication of negative consequences for cow welfare.