Monitoring grazing behaviour of dairy cows in pasture based systems

Continued improvement in the production and utilisation of pastures is essential to maintain the economic competiveness of dairy production systems in Australia. There are varying levels of concentrate feeding for pasture based dairy systems in Australia, ranging from zero concentrate allocation to over 2 tonnes of concentrate per cow per lactation. The optimal amount of concentrates required to achieve the most profitable milk production response is a question commonly asked and the response will be dependent upon several factors. One of the most influencing factors is the rate of substitution. In pasture based systems, it is often difficult to quantify how much pasture a cow substitutes as a result of concentrate feeding. Approaches to quantifying, at an individual animal level, how the grazing behaviour and associated pasture intake of dairy cows changes in response to concentrate feeding should significantly enhance our ability to optimise performance and profitability. This study monitored the grazing behaviour of 24 multiparous cows, in mid lactation, over a 10 day period which were receiving either 6.0 or 0.0 kg DM concentrates per day. Grazing behaviours were monitored visually for three 2-hour periods, per day, for each of the 10 days. There was a significant effect of concentrate feeding level and time of day on grazing behaviour. Cows that were on a diet of 6.0 kg of concentrate per day were observed to spend 41% of their time grazing (defined as “cows in the act of eating”) which was significantly less time than cows on 0.0 kg concentrates, which were observed to spend 67% of their time grazing. Observed grazing time was significantly higher following morning and afternoon milking compared to the period prior to afternoon milking. The coefficient of variation for the percentage of time observed grazing for the cows being fed 6.0 kg of concentrates per day was 0.38 compared with 0.20 for the cows receiving 0.0 kg concentrate. This indicates that the influence of concentrate feeding on time spent grazing, can varying quite significantly between individual cows. Developing automated data collation technology of grazing behaviours as a means for estimating pasture intake and substitution rates would significantly advance the industry’s ability to assess the impact of individually feeding cows to economically optimise performance in a predominately pasture based system.