The effect of pasture allowance and amount of concentrate offered to grazing dairy cows on milk production, dry matter intake, and grazing behavior.

The dairy industry in temperate regions of the world is predominantly pasture-based, with concentrates often fed twice daily in the parlor during milking. Intake of pasture is influenced by the amount of pasture allocated, affecting postgrazing residuals and pasture utilization. This experiment investigated the milk production, DMI, and grazing behavior of dairy cows offered different pasture allowances (PA) and different amounts of concentrate. Thirty-six Holstein-Friesian dairy cows were used in the 25-d experiment, which included two 6-d measurement periods. Three cows were randomly assigned to each of the 12 treatment combinations using a completely randomized design, balanced for DIM and both BW and milk production based on data from the 7 d before the beginning of the experiment. The treatment combinations consisted of offering cows one of 4 PA (20, 35, 50, or 65 kg DM/cow per day; to ground level) and one of 3 concentrate amounts (4, 6, or 8 kg DM/cow per day). Cows swapped PA amounts for each measurement period, but the concentrate amount offered to each cow was unchanged. Average daily milk yield was greater for cows offered PA at and above 35 kg DM/cow per day, as was pasture DMI. Cows offered 6 or 8 kg DM of concentrate per day had a greater average milk yield compared with cows offered 4 kg DM of concentrate per day, but lower pasture DMI. Total daily eating or ruminating time were not significantly affected by either PA or the amount of concentrate fed, but cows offered 4 kg DM of concentrate per day had a greater number of graze bites per day. Finding optimal PA and concentrate amounts to offer is key to adequately feeding cows and managing pasture growth and utilization on pasture-based dairy farms. Because there is considerable variation in geographic region and management strategies of pasture-based farms, which may influence on-farm feed allocation, these data provide information for farmers on what potential benefits they could achieve.