Effects of prepartum stocking density on innate and adaptive leukocyte responses and serum and hair cortisol concentrations

- Reduced prepartum stocking density did not improve immune function of dairy cows.
- Cortisol serum and hair concentrations were not affected by prepartum stocking density.
- Dairy herds may manage to have 100% prepartum stocking density on the day of regrouping.

Objectives were to evaluate the effects of prepartum stocking density on innate and adaptive leukocyte responses, serum cortisol and haptoglobin concentrations and hair cortisol concentration of Jersey cows. The cows (254 ± 3 d of gestation) were balanced for parity (nulliparous vs. parous) and previous lactation projected 305-d mature equivalent milk yield and assigned to one of two treatments: 80SD = 80% stocking density (38 animals/48 headlocks) and 100SD = 100% stocking density (48 animals/48 headlocks). Pens (n = 4) were identical in size and design and each pen received each treatment a total of 2 times (4 replicates; 80SD: n = 338; 100SD: n = 418). A sub-group of cows (n = 48/treatment per parity) was randomly selected on week 1 of each replicate from which blood was sampled weekly from d −14 to 14 (d 0 = calving) to determine polymorphonuclear leukocyte (PMNL) phagocytosis, oxidative burst, and expression of CD18 and L-selectin, and hemogram. The same sub-group of cows was treated with chicken egg ovalbumin on d −21, −7, and 7 and had blood sampled weekly from d −21 to 21 for determination of serum IgG anti-ovalbumin concentration. Blood was sampled weekly from d −21 to 21 to determine glucose, cortisol, and haptoglobin concentrations in serum. Hair samples collected at enrollment and within 24 h of calving were analyzed for cortisol concentration. The percentage of leukocytes classified as granulocyte and the granulocyte to the lymphocyte ratio were not affected by treatment. Treatment did not affect the percentage of PMNL positive for phagocytosis and oxidative burst or the intensity of phagocytosis and oxidative burst. Similarly, treatment did not affect the percentage of PMNL expressing CD18 and L-selectin or the intensity of expression of CD18 and L-selectin. Concentration of IgG anti-ovalbumin was not affected by treatment. Serum concentrations of haptoglobin and cortisol were not affected by treatment. Similarly, hair cortisol concentration at calving was not affected by treatment. According to the current experiment, a target stocking density of 80% did not improve leukocyte responses compared with 100% target stocking density.