Deciphering the immune responses in late gestation Sahiwal cows under different microclimate and its carryover effect...

The current investigation aimed to comprehend the inflammatory and related immune responses in intrauterine calves subjected to heat stress (HS) during late gestation. For this purpose, 48 Sahiwal cows in late gestation were chosen and categorized into four equal groups: naturally heat stressed (NHS), cooling-treated (CLT), spring, and winter, and likewise their neonate calves born in summer (IUHS - intrauterine heat stressed and IUCL - intrauterine cooled), spring, and winter seasons. Environmental parameters were recorded, and the temperature-humidity index (THI) was calculated daily throughout the study period. The average THI values ranged between 84.18 (summer-NHS), 73.88 (summer-CLT), 78.92 (spring), and 64.91 (winter). NHS and spring groups exhibited thermal stress based on THI (> 76.00). Various treatments significantly (P < 0.01) impacted parameters like rectal temperature (RT), respiratory rate (RR), pulse rate (PR), and skin temperature (ST) in Sahiwal cows and their calves during the study, except for heart rate (HR). Blood samples collected during different seasons and from cows housed in a climatic chamber were used to extract plasma. Plasma cortisol, interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α), and thiobarbituric acid reactive substances (TBARS) levels were notably higher (P < 0.05) in the NHS compared to the CLT group. Conversely, total antioxidant capacity (TAC) and immunoglobulin G (IgG) levels were higher (P < 0.05) in the CLT and winter groups. IUHS calves exhibited significantly (P < 0.05) lower overall mean plasma TAC and IgG levels but higher inflammatory and oxidative biomarkers, such as IL-6, TNF-α, and TBARS. Additionally, significant impacts on body weight were observed for factors such as interval (P < 0.01) and the interaction between treatment and interval (P < 0.05), exhibiting consistently lower body weight in IUHS calves throughout the study period. These findings suggest that late gestation heat stress may lead to physiological alterations in future calves. Strategies aimed at mitigating heat stress during late gestation should be considered not only for the productivity and well-being of the pregnant dam but also for the development and future performance of the calf.