Studier av mjölkbarhet automatiskt mätt i mjölkningsanläggningar

Abstract: Milkability or ease of milking, has higher importance today for Swedish dairy cattle producers after the introduction of milking parlours and automatic milking systems. Milkability is the cow's ability to quickly milk out and be completely milked. There are several measures of milkability available. Today the farmer measures the traits subjectively in relation to the conformation scoring of the cow 30-270 days after her first calving. The trait is not included in the total merit indexes for cows or bulls in Sweden. In some milking systems certain milkability traits can be measured automatically, for example maximum flow rate, milk yield and milkingtime. The purpose of this study was to study the variation in these milkability traits, estimate the repeatability and the heritability. The goal was to get an understanding of whether data from automatic milking systems can be used in future for evaluating breeding values for milkability traits. The study covered 2437 cows of SRB and SLB from 20 herds. The two traits that were measured for milkability were the milkingtime and maximum flow rate. The results show that both traits had rather low heritability (0.05) and high repeatability (0.9). Therefore it should be enough with one or two measurements to get reliable results. SLB had higher milk yield, higher maximum flow rate and shorter duration of milking period than SRB. Both breeds were within the limits for optimal milkability considered in earlier studies of the subject. Breed, stage of lactation, calving month, milk yield, and herd all had significant effects on duration of the milking period, whereas lactation number and calving year did not. Breed, stage of lactation, calving year, milk yield and herd had significant effect on maximum flow rate but lactation number and calving month had no significant effect on the trait. There were also big differences between the herds in the study when the traits in the statistical model had been taken into consideration. This shows that environmental effects such as management and milking equipment have great importance for the milkability traits.