Automatic milking and grazing--effects of distance to pasture and level of supplements on milk yield and cow behavior.

In an automatic milking system, 45 cows were divided into groups that grazed on a mixed grass sward (Poa Pratensis and Festuca Pratensis) at different distances from the barn: near pasture (NP) at 50 m between the barn and the pasture and distant pasture (DP) at 260 m between the barn and the pasture. For both of these treatments, 3 kg of dry matter (DM) from supplementary grass silage were offered in the barn. The third treatment group grazed together under the DP treatment but was offered an ad libitum supply of grass silage in the barn (DP + S). Cows were also fed concentrates in relation to requirements (average 7 kg/d per cow). During the period from June 5 to July 13 (Period 1), cows in the NP group had a higher milk yield (29.1 kg) than did cows in the DP group (26.4 kg) and had a higher milking frequency compared with the other groups, 2.5 vs. 2.3 and 2.3 milkings/d, respectively. During August, cows in group DP + S had a lower milking frequency (2.1 milkings/d) compared with the two groups on lower supplementation (2.5 milkings/d). In Period 1, all groups spent approximately 20% of their time grazing, but after mid July groups DP and DP + S decreased the time they spent grazing to around 10%; cows in group NP continued to graze as before. Thus, longer distances to pasture may lead to decreases in milk yield, milking frequency, and grazing time of cows in an automatic milking system. The higher level of silage supplementation (group DP + S) did not result in a significantly higher milk yield compared with herd-mates (DP) also grazing the more distant pasture.