Inverkan av betessläpp på celltal och mjölkkvalitet hos mjölkkor

Abstract: In Sweden regulations stipulates that dairy cows are kept on pasture, or given the opportunity to spend time outside during a coherent period of between two to four months, depending on region. The transition out to pasture is a big change from the winter period in the stable, especially for the modern high yielding dairy cows. The let out to pasture includes a change in feed, environment, and new routines. There are indications that the milk somatic cell count (SCC) rises in a peak shortly after the let out. The purpose of this study was to see if peaks in the SCC could be observed after the let out, and to study the contribution of inflammatory cells (neutrophils) and if the milk composition are affected. The study included 35 cows that were kept in stable during the winter. The cows were both primiparous and multiparous and of various DIM (days in milk), from 12 to 442 days at the beginning of the study. The study was running over 16 days. Milk samples for SCC, differential cell count, fat, protein and lactose were collected 10 days before the let out to pasture and 5 days after. Samples for free fatty acids (FFA), casein and whey protein were collected one day before and at 1, 3 and 5 days after the let out. During day 3 and 5 these samples were taken only from cows that had at least doubled their cell count day 1. The result showed that the SCC increased immediately after the let out to pasture. The highest values were recorded in the evening the same day as the let out and then declining, but were significantly higher trough the whole study. The neutrophil percentage followed the SCC changes fairly well in a way that is commonly seen, although the peak value was recorded later. The first morning milking after the let out the milk yield was significantly lower, but thereafter the yield was higher or unaffected. The milk components were affected mainly in a positive way. The protein and fat percentage increased and lactose content was un-altered, except for the first milkings when they decreased. The casein levels increased, whey proteins where not affected in the afternoon milk, but in the morning milk there was an increase. FFA decreased after the let out and stayed significantly lower until the end of the study. The conclusion was that the let out to pasture led to an increase in the SCC after the let out, but that it overall affected the milk quality in a good way.