The Effect of Frequency of Fresh Pasture Allocation on Pasture Utilisation and the Performance of High Yielding Dairy Cows

SIMPLE SUMMARY: Pasture remains a large component of the diet in many dairy systems across temperate regions. However, animal performance in pasture-based systems is often limited due to the lower dry matter intake (DMI) achieved within these systems, meaning animals fail to perform to their genetic potential. Providing a high herbage allowance can improve DMI and subsequently animal performance at pasture, however such methods result in reduced pasture utilisation rates, decreasing the cost-effectiveness of the pasture-based system. Methods that support high levels of animal performance whilst maintaining high pasture utilisation efficiency are required to support efficient and sustainable pasture-based systems. Hence, the aim of this study was to investigate the impact of different frequencies of pasture allocation (12, 24 and 36 h (h)) on pasture utilisation and the performance of high-yielding dairy cows. The results from this study indicated that 36 h allocations best supported the performance of primiparous animals. The 36 h allocations were also associated with significantly higher pasture utilisation efficiency than 12 h allocations during the first study period, but this was not replicated in the second period, where utilisation was similar across all treatments. ABSTRACT: Pasture allocation frequency (PAF) can influence pasture availability and grazing behaviour, which subsequently may impact on animal performance. Limited research to-date has investigated grazing management methods to improve the performance of high production dairy cows whilst also achieving high grass utilisation rates. This study evaluated the effect of three different PAF’s (12, 24 and 36 h) on pasture utilisation, the performance of high yielding dairy cows and the interaction with parity. The experiment included two 60-day periods, 90 spring calving dairy cows (27 primiparous animals) in period one and 87 (24 primiparous animals) in period two. The average pre-grazing sward height (11.4 cm) was similar for all treatments in both periods. In period one, pasture utilisation rate was significantly higher (8%) in the 36 h compared to the 12 h treatment. In period two, milk energy output was significantly greater for primiparous animals in the 36 h treatment relative to the other treatments.