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For decades there have been discussions about the necessity and optimal length of dry cow periods. Yet, there is still a lack of information referring to special questions. The effects of dry period length on metabolism and productive efficiency are particularly well studied. However, there are hardly any studies investigating udder health, although udder diseases stand next in line to reproductive issues and lameness problems, when looking into reasons for culling.
The objective of this study was to investigate the impact of different dry period lengths on udder health in the subsequent lactation. Therefore, a four week dry period was compared to a standard eight week dry period. This study was conducted between April and October 2006 on the research farm of the Landesanstalt für Landwirtschaft, Forsten und Gartenbau Sachsen-Anhalt.
Data from 75 cows were analyzed in this study. Cows were enrolled in one of two groups: group L (long) with an eight week dry period (n = 39 cows) and dry-off at day 56 prior to calving, and group S (short) with a four week dry period (n = 36 cows) with dry-off at day 30 prior to calving. Cows in group L were fed a low energy diet from dry-off until day 30 prior to calving. Then all cows were fed a moderate energy diet. Multiple milk samples for cyto-bacteriological analysis were taken before dry-off and after calving. Clinical examinations, i.e. inspection and palpation of the udder, were performed at dry-off and prior to calving. Farm documentation was included in the statistical analysis.
The results show that cows with a shortened dry period had higher somatic cell count in milk for at least one week after the onset of lactation, compared to cows with eight week dry periods. Furthermore, it was found out for cows of both groups that non-physiological udder forms are associated with higher somatic cell count in milk before dry-off. Asymmetric udders are associated with higher somatic cell count in milk 21 days after calving. Short dry periods are detrimental for milk production.
In conclusion, a shortened dry period can have a detrimental impact on milk production and somatic cell count. Cows with increased somatic cell count in their previous lactation should still be subjected to an eight week dry period to assure sufficient udder regeneration. Farms with high somatic cell count should take this into consideration when determining their dry period length. It is recommended that one should conduct clinical udder examination and determination of somatic cell count before selecting the appropriate dry period length. Based on these findings, it is possible to assume how subsequent lactation may develop for any cow. Asymmetric udders and high somatic cell count at dry-off are strong arguments against a shortened dry period.