A New Management for Dry-Period
Innovative Management of Quebec Dairy Herds: Rethinking the Drying-off PeriodXin Zhao, Pierre Lacasse
The lactation cycle of dairy cows must include a period without production, called the dry period, so that optimal milk production can be achieved during the following lactation. Although this period is very important for the renewal of udder cells, the cow is very vulnerable to new infections during the active involution that follows the end of milking. It was established that the risk of intramammary infection at calving increases by 77% for every 5 kg of milk produced over 12.5 kg during the last day of milking. Since nowadays it is not uncommon to dry off cows that produce over 30 kg, it is clearly advantageous to reduce milk production before the dry period. The most commonly used method, dietary restriction, creates a metabolic stress. The goal of this project was to develop new approaches to reduce milk production come drying-off time and accelerate the involution of the mammary gland without disturbing cows’ metabolism. Two types of approaches were explored: the first was to reduce milk production at the time milking was to stop by decreasing the strength of the lactogenic signal, and the other was to accelerate the expression of mammary gland regression mechanisms. Decreasing the strength of the lactogenic signal using a prolactin inhibitor, quinagolide, rapidly reduced milk production and accelerated involution without disturbing the cows’ metabolism and immune resistance. A drastic food restriction also reduced milk production and accelerated involution, but caused metabolic stress and induced immunosuppression. A short-day photoperiod also helped weaken the lactogenic signal and caused a moderate decrease in milk production. Lastly, intramammary infusion of casein hydrolysates on drying-off day accelerated the involution of the mammary gland.