Effects of take-off level at udder quarter level and feeding during milking on milk fat quality and milk somatic cell count in an automatic milking system

Sammanfattning: The number of dairy farms in Sweden is decreasing, while the number of cows per farm is increasing. Since milking is very labour intensive many farmers have invested in new technology like automatic milking system (AMS) in order to reduce the work load. To increase the milking efficiency, it is important to have set take-off level of the milking cluster at a milk flow rate that minimize the time the cows spend in the AMS without affecting the milk yield and quality. Previous studies have indicated that milk yield decreases with increased take-off level when the take off level is set at milk flow from whole udder level. Furthermore has it been observed that feeding during milking might affect the milking time and milk yield. The aim of the present study was to examine how the take-off level of 100 g/min, 300 g/min, and 500 g/min at udder quarter level combined with or without feed during milking influenced the milk yield, milk fat globule size, content of cholesterol and beta-hydroxybutyrate in the milk, and the milk somatic cell count when the cows were milked in AMS. In the study, 30 cows of the breeds SRB (N=21) and Swedish Holstein (N=9) were included. The study lasted for six weeks and each treatment period was seven days. The treatments were arranged in a 6x6 Latin square to include all combinations of treatments every treatment period. Milk samples were taken during five milkings during the last two days of each treatment period. Samples taken for analyses of milk composition were collected during all five milkings, samples for the fat analysis were collected one milking each treatment period and determination of residual milk and samples from the residual milk were collected during the last milking every second treatment period. Milk samples from separate udder quarters were collected for analyses of milk composition during two milkings and for fat analysis during one milking. The results showed that the amount of milk was not affected by the different take-off levels, but total milking time was shortened with 0.5 min if using a take-off level on 500 g/min compared to a take-off level on 100 g/min (P < 0.001). There was no difference in milk fat globule size, milk cholesterol or milk somatic cell count between the different treatments but beta-hydroxybutyrate was greater in take-off level 500 g/min compared to take-off level 100 g/min (P < 0.05). Feeding during milking had only effect on milking time, which gave a longer milking time compared to no feeding during milking (P< 0.001).