The effect of grazing intensity on the performance of high‐yielding dairy cows

Abstract

The study evaluated the impact of High, Moderate and Low grazing intensities throughout the grazing season, within a rotational stocking system, on the performance of high‐yielding dairy cows receiving a high level of concentrates. Sixty‐three Holstein‐Friesian dairy cows, 21 at each grazing intensity, were rotationally grazed. Average paddock size, post‐grazing sward heights and seasonal grazing stocking rates within the High, Moderate and Low grazing intensities were 0.143, 0.167 and 0.200 hectares, 5.2, 6.1 and 6.8 cm and 7.8, 6.7 and 5.6 cows ha−1 respectively. Grazing intensity had no effect on milk fat and protein content, end‐of‐study body condition score or end‐of‐study live weight although the latter tended towards significance (p = .057). Average daily milk yield per cow was higher within the Low grazing intensity (33.2 kg day−1) than High grazing intensity (30.5 kg day−1), and average daily fat‐plus‐protein yield was higher for Low and Moderate than High. Milk output per hectare was higher for the High grazing intensity than Low grazing intensity (33,544 and 26,215 kg ha−1 respectively). Grazing intensity had no effect on grazing bite number, blood metabolites or concentrations of milk fatty acids or on sward morphological components, although dead matter increased with time across all grazing intensities. Herbage utilization efficiency (above 1,600 kg DM ha−1) was 52%, 74% and 87% for Low, Moderate and High respectively. It is concluded that high‐producing dairy cows can graze at high levels of utilization when they are receiving high rates of concentrates. Although cow performance will be reduced, milk yield per ha will increase.