Early mammary gland metabolic and immune responses during natural-like and forceful drying-off in high-yielding dairy cows

Abstract

The present work compared metabolic and immune responses in genetically high-producing cows that produced a low amount of milk before expected involution and in cows with the same genetic potential that produced copious amounts of milk before their scheduled drying-off. Ten multiparous lactating Israeli Holstein cows producing approximately 10,500 L in the current lactation, without bacterial infection and scheduled for drying-off approximately 60 d before their expected parturition, were studied. Five of the cows that exhibited a sharp, spontaneous reduction in milk yield at the end of their lactation and produced less than ~14L/d were defined as cows approaching natural involution (ANI), and 5 cows that produced between 25 and 35 L/d were defined as cows approaching forced involution (AFI). Three days before scheduled drying-off, milking was stopped and milk samples were collected from each quarter. After milking cessation, only modest swelling was observed in the udders of the ANI cows. In the ANI cows, lactose and fat concentrations decreased and the fat:lactose concentration ratio indicated that on d 1 and 2 fat concentrations decreased faster than lactose concentration, whereas on d 3, the rate of reduction was about the same for lactose and fat. In contrast, in AFI cows, fat concentrations increased on d 1 and the fat:lactose ratio indicated that changes in fat secretion were minor compared with those of lactose secretion. Rennet clotting time of milk after drying-off in the ANI cows increased, whereas curd firmness decreased rapidly, such that mammary secretions did not coagulate on d 3. In the AFI cows, such significant changes were observed only on d 3. The inflammatory response increased in both groups, but at each stage the increase was greater in ANI cows than in AFI cows. On d 1, the increase in leukocyte numbers in the ANI cows was made up of mononuclear cells (i.e., T lymphocytes and macrophages). In contrast, in the AFI cows, we observed a marked increase in leukocyte numbers, mainly in the form of polymorphonuclear cells. Our data indicate that the abrupt mammary involution induced in AFI cows provoked signs of distress, which were associated with neutrophilia in milk. In contrast, in the ANI cows, cessation of milking occurred without evidence of engorgement of the udder. Physiological differences in ANI and AFI cows are distinct and are reflected in the differences in the leukocyte populations in milk.

Invited review: Cessation of lactation: Effects on animal welfare

“…Hence, monitoring for an inflammatory response could be a useful indicator of any tissue damage caused by abrupt cessation of milking, which is pertinent because this practice has been receiving increasing criticism (e.g., Bertulat et al, 2013). This hypothesis is supported by work showing that although mammary glands with low engorgement do exhibit some inflammatory response (likely due to a backlog of clearing of dead cells), the cell types involved in the inflammatory response are different when engorgement is high (Silanikove et al, 2013). This difference led the authors to conclude that abrupt mammary involution associated with sudden cessation of milking causes distress in high-producing cows.…”

“…Interestingly, recent evidence suggests milk production level affects leukocyte populations. For example, cows that entered the dry period producing less than 14 kg/d produced higher numbers of lymphocytes and macrophages, giving the mammary glands a more effective antibacterial response when compared with cows producing more than 25 kg/d (Silanikove et al, 2013). Clearly, the beginning of the dry period is a high-risk time for IMI, but this risk can be decreased by reducing milk production before dry-off.…”

“…Cows entering the dry period with high milk production are more likely to develop IMI (Rajala-Schultz et al, 2005). Furthermore, these high-production cows experience more milk leakage, have delayed teat canal plug formation, as well as display differences in mammary gland response to infection (Bertulat et al, 2013;Silanikove et al, 2013). All this occurs in spite of widespread dry-off therapy use.…”

Behavior and welfare of dairy cows submitted to drying: Review

“…Uma das experiências que as vacas passam quando não há redução da produção de leite antes da secagem é a dor (Silanikove et al, 2013). A dor pode ocorrer após a interrupção abrupta de ordenha, e está associada com a pressão no úbere, capacidade de armazenamento atingida e aos danos causados nos tecidos da glândula mamária (Bertulat et al, 2013).…”

“…Em seu estudo de secagem de vacas com produção de 25 kg de leite/dia, Silanikove et al (2013) sugeriu que o aumento de vocalizações era indicativo de úbere cheio de leite ou inchado com ingurgitamento, e causa de dor.…”