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Automatic milking and grazing

One of the major concerns with automatic milking is whether it can be successfully combined with grazing. The main reason for that concern is that pasture is an important feed source for cows in many countries. During recent years the interest for animal welfare and health has also led to an increased interest in pasture and grazing. The role of grazing animals for the amenity of the landscape and for biodiversity must also be considered, as well as the need to find management systems that include grazing for organic farmers interested in automatic milking.

On-farm studies and surveys performed on AM farms with grazing have shown that there is a large variation among farms in grazing time allowed. In a Danish on-farm study no significant relationship between the time cows spent on pasture (5.4-20.6 hrs) and the total number of milkings per 24 hours (2.1-2.8) was found. In a Dutch experiment with 24 lactating cows however, where zero grazing was compared with 12 and 24 hours of grazing, animals with 24-hour access to pasture had a significantly lower average milking frequency (2.3milkings/day) than the other treatments (2.5-2.8milkings/day). On farms where the cows had free admission to the pasture area most of them went out immediately after the door was opened in the morning, showing that they were eager to use the opportunity to graze. There were fairly large differences between the amount of time that was spent fetching cows late for milking, but farms normally used around 10-20 minutes daily.

In experiments with about 64 cows, the effects of distance between pasture and barn and level of roughage supplements (maize silage) were studied during 2002 and 2003. No significant effects of distance between barn and pasture or the level of maize silage supplements on milk yield, milking interval or number of fetched animals were found.

In another experiment that also focused on the effects of distance and level of roughage supplements 24 hour grazing was applied throughout the season. The group grazing near the barn had a significantly higher milk yield (kg), longer pasturing time and shorter milking interval than the group grazing at a longer distance.

To encourage cows to return to the barn regularly, many farms that practice AM milking and grazing have chosen to offer the cows drinking water in the barn only. However, it has also been argued that this practice may lead to a lower water intake, which in turn could lead to a lower milk yield. There have also been concerns about animal welfare. The effect of offering cows drinking water in the barn only was compared with offering drinking water both in the barn and out on the pasture in two experiments. No significant differences in water intake, milk yield or milking frequency were observed.

Two cow traffic systems were compared during the grazing season, free and controlled cow traffic. At the start of the grazing season the herd was divided into two groups. Free cow traffic gave a significantly lower number of milkings (per cow and day) and a significantly lower number of voluntary milkings compared with controlled cow traffic. The average number of animals to be fetched increased as the season progressed and was higher for the cows with free than with controlled cow traffic. A trend for decreasing visiting and milking frequencies was seen over time.

Possibilities of using individual auditory signals to stimulate cows to go to the milking unit were explored. Preliminary results indicate that animals need a longer training period and perhaps a better reward system if auditory signals are to be used to entice the animals to go to the milking unit.

General conclusions.
It is possible to combine automatic milking and grazing. The utilization of the milking unit may be slightly lower during the grazing season, especially when animals are allowed to graze many hours per day due to a more uneven distribution of milkings over the 24-hour period. To maintain smooth cow traffic it is therefore advisable not to maximise the number of lactating animals in the barn during the grazing months. In the long run, it appeared beneficial in terms of labour not to be too eager to fetch the cows but to give them the chance to return voluntarily. Good production results can be obtained with longer distances between barn and pasture but distance may affect number of cows that need to be fetched. There are indications that feed supplementation strategy can be used as a management tool to achieve well-functioning cow traffic during the grazing season.

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