Voluntary automatic milking in combination with grazing of dairy cows: Milking frequency and effects on behaviour

Abstract

Automatic milking systems (AMS) enable cows to be milked without human interference. Such systems are more acceptable to consumers and from the animal welfare point of view if they can be combined with grazing in the summer season. In this study, grazing was combined with fully automatic milking for a group of 24 crossbred Holstein–Friesian cows. It was assumed that the cows would visit the AMS voluntarily. Zero grazing (G0) was compared with restricted grazing (cows could spend up to 12 h outdoors daily; G12) and unrestricted grazing (cows could spend up to 24 h daily at pasture; G24). The AMS was continuously available in the cowshed adjacent to the pasture of 1.5 ha. Water was available in the barn, but not at pasture. The average daily milking frequency was 2.3 in G24 compared with 2.5–2.8 in the other treatments ( p<0.01). The reason was that the cows spread their visits to the AMS less evenly over the day in G24 (more visits in the afternoon and less visits at night; p<0.01). In the grazing treatments, the cows spent more time eating forage ( p<0.01). The lying times did not differ between the treatments, but the cows lay between 80 and 99.6% of their total lying time at pasture when they had the opportunity to be outdoors. In the grazing treatments, cows entered or left the barn in the company of at least one other cow in 76.6 to 90.7% of the cases. The cows' arrival times at the barn or pasture were not randomly distributed ( p<0.01). In G24, cows spent less time in the pasture between 1000 and 1700 h when the Black Globe Humidity Index was high ( p<0.01), and, related to that, a likeliness for conditions of heat stress. It was concluded that automatic milking on a voluntary basis can indeed be combined with grazing. Grazing seems to be advantageous for the welfare of the cows, as they clearly preferred to lie in the pasture rather than in the cubicles. For the farmer, restricted grazing is more reliable than unrestricted grazing, as milking frequency will be higher on average. Farmers wishing to apply automatic milking with grazing should manage this flexibly, in accordance with ambient conditions, as the weather affects cow behaviour.