Milk flow traits, milking management and udder health in dairy cows

The present thesis investigated the sources of variation of milk flow trait in dairy cows and the relation with milking management and udder health. Four different studies were conducted. Milk flow curve was recorded by electronic milk flow meters. In the first study, primiparous cows were monitored during the whole lactation. The most interesting parameters were: time of milk ejection, time of plateau phase, frequency of bimodal curve and overmilking phase. The individual effects and interactions of vacuum level, B-phase duration, and liner compression on milk flow traits were investigated in the second research. Liner compression had an influence in increasing peak milk flow, relieving teat congestion. The third study was carried out to understand milking machine factors that contribute to teat-end hyperkeratosis (HK). The effect of liner on HK was investigated. The liner characterized by the thickest wall promoted the best teat apex condition. One further investigation on liner type and milking management effects on milk flow traits and HK was performed. Overmilking had the strongest effect on HK. Milk flow parameters, udder health and teat condition are closely link each other. Animals result to be more resistant to poor udder health and bimodal curve if they have a long plateau phase (>40% of machine on-time), a low peak milk flow (<4 kg/min) and a low milk electrical conductivity (<6.5 mS/cm). Milk flow trait study can be a useful tool to identify cow characteristics.