The aim of the present study was to investigate whether milk composition and milk yield are changed in relation to a moderate increase in milk somatic cell count (SCC) in separate udder quarters. During a period of 13 weeks, 4158 bulk quarter milk samples from 68 cows were collected and analysed for milk SCC and milk composition. The sampling was done twice weekly. The cows were in different stages of lactation and in different lactation numbers. For calculations, three groups of cows were formed according to their SCC value. Group 1 cows, where all quarters had an SCC <100,000 cells/ml at all sampling occasions, were considered to be non-affected. Group 2 cows had one udder quarter with an increased SCC >100,000 cells/ml and 1.5-fold higher than the opposite quarter at one sampling occasion. For group 3 cows, the increase in SCC remained for several consecutive sampling occasions. Data from group 1 cows revealed that front and rear quarters were similar when compared with each other. For group 3 cows, the lactose content in milk decreased significantly, simultaneously with the increase in SCC and remained decreased for two sampling occasions after the initial increase in SCC. It was concluded that deviations in lactose content within front and rear quarters, respectively, may be a useful tool for detection of moderately increased SCC in separate udder quarters.

During the last several decades, new milking management systems have been introduced, of which development of automatic milking (AM) systems is a significant step forward. In Europe, AM has become an established management system and has shown to be much more than milking management. Factors such as milking, milk quality, feeding, cow traffic, grazing, and animal behavior are essential elements of AM. This system offers possibilities for more frequent milking and can be adapted to lactational stage. Increased milk yield with AM has been observed, but lack of increased production has also been reported from the field, probably due to less attention paid to the total management system. The AM system provides consistent milking routines, with those for teat stimulation and feeding during milking giving an adequate oxytocin release and milk ejection. Initially, reduced milk quality, such as increased FFA, total bacteria count, and somatic cell count (SCC), was observed. Increased FFA could be due to increased milking frequency or handling of the milk, although this has not yet been determined. The elevated total bacteria count was probably due to mismanagement because later studies indicated that teat cleaning in AM is sufficient to reduce spores and dirt on the teats. Significant positive effects on udder health and teat treatment were observed in some studies, possibly as an effect of quarter milking, a procedure whereby an individual teat cup is detached when milk flow is below the preset level for detachment. Well-functioning cow traffic is a prerequisite for successful AM system performance to obtain an optimal number of visits to the feeding area and the milking parlor for all cows. Technical stoppages in the AM system (i.e., the milking unit) increased milk SCC, and the variation and length of the milking interval seem to contribute to elevated SCC. Grazing is a common management routine in many countries. Different ways to motivate the cows to visit the milking parlor, such as shorter distance between barn and pasture, supplement feeding, access to water, and use of acoustic signals, have been tested. It was concluded that use of AM and grazing systems together is possible as long as the distance from the milking parlor to pasture is short. With proper management routines, it is possible to achieve a production level and animal well-being in AM systems that are at least as good as in conventional milking systems.

The objective of this study was to investigate how useful data from automatic milking systems used in commercial herds are for genetic analysis of milkability traits. Data were available from 4,968 Swedish Holstein and Swedish Red cows over a span of 5 yr (2004-2009) from 19 herds. The analyzed milkability traits were average flow rate, box time, milking interval, and number of milkings per day. Variance components were estimated for genetic, permanent environmental, and residual effects in first and later (second and third) lactations, and were used for estimation of heritabilities and repeatablilites. The experiences of the data quality and editing procedures showed that almost half of the data and about a quarter of the cows had to be excluded from the analyses due to incomplete or inconsistent information. However, much more data are available than is needed for accurate genetic parameter estimations. For the genetic analysis, a repeatability animal model was used that included the fixed effects of herd, year and season, lactation month, and milk yield. The repeatability coefficients were at a high level: highest for average flow rate, with estimates between 0.8 and 0.9. The estimated heritability coefficients were in the range of 0.37 to 0.48, 0.21 to 0.44, 0.09 to 0.26, and 0.02 to 0.07 for average flow rate, box time, milking interval, and number of milkings, respectively. The results from the present study unraveled large genetic variation in milkability traits. The genetic parameter estimates were well in agreement with previous studies of milkability, which proves the feasibility of using data from automatic milking systems for genetic analysis.

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