Factors associated with extended milking intervals in a pasture-based automatic milking system

In pasture-based automatic milking systems (AMS) cow traffic and behaviour are markedly different and generally cows achieve lower milking frequencies (MF, defined here as the number of milking events/cow in a 24 h period) and lower milk production levels in comparison to indoor systems. In this study, a total of 151,893 individual milking records collected from the FutureDairy pasture-based AMS research farm during 2007 and 2008 were analysed to examine relationships between cow traffic related variables and cow performance. In addition, factors specific to pasture-based systems, such as proportion of pasture in the diet, pasture allowance, distance to pasture allocation and pre-grazing pasture cover, were explored to understand their association with occurrence of different milking intervals (MI, defined here as the amount of time elapsed between consecutive milking events, measured at every milking session in hours since the previous milking event). Although there was a wide range of MI and MF, higher MI were associated with greater milk yields per milking. Yet, efforts should be focused on reducing the occurrence of MI above 16 h, because secretion rate beyond that threshold tended to decrease. Increasing MF was associated with greater daily milk yield for cows in all stages of lactation. Overall, longer MI were observed in late lactation and primiparous cows. Additionally, an increase in distance between the paddock and the dairy up to 500 m appeared to be unrelated to a change in MI, but higher MI were observed with distances from the dairy facility between 500 m and up to 1 km. Pre-grazing pasture covers above 3000 kg DM/ha or below 2000 kg DM/ha were associated with shorter and longer MI respectively. For every 5 kg DM/cow increase in pasture allowance above 10 kg DM/cow, there was a 10-15 min increase in MI. Modifying management practices to accommodate these factors specific to pasture-based systems could allow for increased MF and higher total milk yield per cow.