Milking interval, milk production and milk flow-rate in an automatic milking system

One of the characteristics of automatic milking is that cows can visit the milking robot voluntarily. This induces a large variation in the frequency of visits to the milking robot and, thus, results in a large variation in milking intervals. The relationships between milking interval, milk production and milk flow-rate using a milking robot were studied with data from a research farm (66 cows) collected between October 1997 and September 1999 (107 785 milkings). The average milking interval was 9.2 h (S.D. = 3.3). The average milk flow-rate was 2.5 kg/min (S.D. = 0.79) and the average milk production was 1.3 kg/h. There was a large variation in milking intervals. Respectively, 9.7 and 17.6 percent of the milkings had an interval shorter than 6 h or longer than 12 h. In this variation, cow factors do play a role. Of all cows, 6% had an average milking frequency of less than twice per day. Cow factors and time of the day contributed to the variation in milking interval. In addition to cow factors, the length of the milking interval had a significant effect on milk production and milk flow-rate. The effects of milking interval on milk production per hour were greater for higher producing cows than for lower producing cows. The variation in the milking interval could be part of the explanation for an apparent increase in SCC with automatic milking. Optimisation of the milking frequency and thus the milking intervals is important. This optimisation should consider effects of milking interval on milk production, capacity of the automatic milking system and udder health. (C) 2001 Elsevier Science B.V. All rights reserved.