The effect of incomplete milking or nursing on milk production, blood metabolites, and immune functions of dairy cows.

During the transition from pregnancy to lactation, the sudden increase in nutrient demand for milk production causes metabolic perturbations and is associated with immunosuppression and a high incidence of metabolic and infectious diseases in high-yielding cows. In this study, we examined whether limiting milk harvest postpartum while maintaining milking stimulus could improve the metabolic status of cows without reducing overall milk production. Forty-seven Holstein cows were milked completely twice a day from calving (control); milked incompletely (about one-third of expected milk production was collected) twice a day until d 5 after calving (incomplete); or left to nurse their calf until d 5 and milked once a day from d 3 to d 5 (nursing). All cows were milked twice a day from d 6 to the end of the experiment (d 61). During the treatment period (d 1 to 5), milk production averaged 27.3 and 9.7 kg/d for the control and incomplete treatments, respectively. We observed no residual effect of treatment on milk production, which averaged 47.8, 45.7, and 46.4 kg/d for the control, incomplete, and nursing treatments, respectively, between wk 2 and 9. The dry matter intake of the cows was similar during and after treatment. From wk 2 to 9, milk protein and lactose percentage were not affected by treatments, but milk fat tended to be higher in control cows than in cows milked partially (incomplete + nursing). Blood concentrations of glucose and phosphorus were lower and concentrations of nonesterified fatty acids and β-hydroxybutyrate were higher in control cows than in partially milked cows during the treatment period. The positive effects on glucose and β-hydroxybutyrate remained significant up to d 28. Peripheral blood mononuclear cell (PBMC) proliferation and secretion of IL-4 were depressed during the postpartum period, and proliferation tended to be greater for cells incubated in serum from cows in the incomplete treatment on d 5 but lower on d 61. We observed no effect of treatments on polymorphonuclear neutrophilic leukocyte chemotaxis or phagocytosis. Proliferation and IL-4 secretion of PBMC were negatively correlated with concentration of serum nonesterified fatty acids. Reducing milk harvest postpartum while maintaining milking stimuli reduced metabolic stress without compromising productivity of high-yielding dairy cows.