The effect of dry-period heat stress on inflammatory, oxidative and metabolic alterations, and acquired immunity in dairy cows and offspring

Abstract

This study aimed to investigate the effects of dry-period heat stress on metabolic and oxidative stress parameters, cytokine release, and T lymphocyte percentages in dairy cows and their offspring. Thirty-two Holstein cows were randomly assigned to heat stress (HS) and cooling (CL) groups. Blood samples were collected to harvest serum and isolate peripheral blood leukocytes, from cows at 21 – 28 days before the expected calving date and immediately after calving, and from their calves postnatally (before colostrum consumption and 24 ± 1 h after birth). Helper (Th1, Th2), regulatory T (Treg), and gamma/delta T (γδT) lymphocytes were enumerated by flow cytometry. Interferon gamma (IFN-γ), tumor necrosis factor- alpha (TNF-α), Interleukin-17A (IL-17A), IL-10, IL-6, IL-1β, retinol, alpha-tocopherol, lactoferrin, and immunoglobulin G (IgG) levels were measured using bovine-specific commercial enzyme-linked immunosorbent assay (ELISA) test kits. Nitric oxide, paraoxonase, total oxidant capacity, total antioxidant capacity, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase, malondialdehyde (MDA), albumin, total protein, cholesterol, bilirubin, and creatinine levels were measured using an auto-analyzer. Compared to the CL group, in the HS cows, serum retinoic acid, alpha-tocopherol (p < 0.05), ALP, catalase, GSH-Px and IL-1β levels (p < 0.01) were significantly lower, whereas IL-6, IFN-γ and IL-10 levels were higher (p < 0.01). The HS cows presented with higher Th1 lymphocyte percentages (p < 0.01), and lower γδT and Treg lymphocyte percentages (p < 0.01). Treg lymphocyte percentages showed no difference between the groups, but varied by day. Specifically, in both the HS and CL dams, Treg lymphocyte percentages were significantly lower at the calving time than on day 21 before the expected calving date (p = 0.021). Colostral IgG concentrations were lower (p < 0.05) in the HS group. In the offspring, there were no significant differences between the HS and CL groups for the T lymphocyte percentages before colostrum consumption and the serum IgG concentrations at 24 ± 1 h after birth. In conclusion, the study findings suggest that providing heat stress abatement to dry cows may modulate both Th1, Treg, and γδT lymphocyte functions, and the release of pro-inflammatory and anti-inflammatory cytokines. However, intrauterine heat stress did not affect lymphocyte percentages in offspring before colostrum consumption.