Management of dairy cows to improve resistance to infectious diseases

Abstract Text: The incidence of infectious diseases varies greatly during the lactation cycle. Most new cases of clinical mastitis appear at the beginning of lactation (transition period), and the incidence increases with the level of milk production. In addition to mastitis, the majority of other infectious diseases becomes clinically apparent during the first 2 wk of lactation. During this time, cows are in negative energy balance and they must mobilize body reserves to balance the deficit between food energy intake and energy required for milk production. Cows undergoing energy deficit have a weakened immune system, which increases their susceptibility to infections. Therefore, we evaluated the effects on blood metabolite concentrations and immune functions of limiting milk production in early lactation in order to reduce the negative energy balance. In a first experiment, multiparous Holstein cows were milked either once a day or twice a day for the first postpartum week. In a second experiment, the amount of milk harvested was limited by milking cows incompletely (about one third of expected milk production was collected) twice a day until d 5 after calving. In a third experiment, first wk milk production was limited by administering a prolactin secretion inhibitor, quinagolide, during the first days of lactation. Globally, the results of these studies indicate that reducing the amount of milk harvested postpartum while maintaining milking stimuli reduces metabolic stress and immunosuppression without compromising productivity of high yielding dairy cows.  The second period that has the highest incidence of new intramammary infections (IMI) is the period immediately following drying-off, during early mammary gland involution. The importance of the dry period is often underestimated as many of these new infections are only detected after the next calving. A cow’s risk of acquiring a new IMI during the dry period increases with milk production at drying-off but decreases as mammary gland involution progresses. In this context, we tested whether prolactin inhibition could be used to reduce milk production at drying-off and to accelerate the rate of mammary involution after cessation of milking. In late-lactation cows, quinagolide decreased milk production within the first day of treatment and induced more rapid changes in concentrations of several markers of mammary gland involution after drying-off. In addition, quinagolide improved the resistance to IMI suggesting that prolactin inhibition could be a new strategy for facilitating drying-off. Innovative management can be used to reduce dairy cow’s susceptibility to infection and antibiotic utilisation.

Keywords: mastitis, transition period, blood metabolites