Supplementary feeding of forage to grazing dairy cows. 1. Offering hay to dairy cows at high and low stocking rates

For three 8‐week periods of the grazing season 48 spring‐calving cows were continuously stocked at either a high or a low rate (average 4.9 and 4.3 cows ha −1 respectively) which declined through the season. Within each stocking rate group half the cows were allowed access to hay for 45 min after morning milking; the other half received no hay. Total dry matter (DM) intakes were increased by offering hay, and intakes of hay were greater at the high stocking rate and during prolonged periods of inclement weather. However, there were times when, because of low herbage height and adverse weather, offering hay once daily could not prevent a decline in total DM intake. Grazing time was reduced and ruminating time increased by offering hay, but the rate of biting at pasture was unaffected. Hay DM was eaten at twice the rate of intake of herbage DM. Offering hay increased milk yield in early season and liveweight gain in late season. The benefits of offering hay were greatest for the higher yielding cows. There were no significant effects on milk composition. Stocking rate had only small effects on herbage height, but stocking at the higher rate tended to reduce herbage DM intake and reduced live‐weight gain in late season. Levels of utilized metabolizable energy from grazed herbage were high (average 106 GJ ha −1 ) but were reduced by feeding hay and stocking at the lower rate.