Heat Stress Impacts Immune Status in Cows Across the Life Cycle

Abstract

Heat stress has a myriad of effects on dairy cattle across the life cycle. Whereas, the most commonly recognized impacts are associated with production responses, emerging evidence indicates that heat stress profoundly alters the immune response of calves and cows, from the prenatal stage through lactation. For example, in utero heat stress reduces passive immune transfer regardless of colostrum source, relative to normothermic conditions in late gestation. Dry cows exposed to heat stress have lower immunoglobulin responses to ovalbumin vaccination, but this effect dissipates with cooling following parturition. Conversely, cows under heat stress when dry exhibit carryover effects on the innate arm of the immune system in early lactation. In this paper we review the effects of heat stress throughout the life cycle of the dairy cow, with particular emphasis on the impact of heat stress during late gestation on the cow and the developing fetus, both before and after parturition. In addition, the impact of altered immune status under heat stress on other physiological systems, especially those supporting milk production, are considered. Finally, management interventions to prevent and reverse the effect of heat stress are presented.

The Effect of Stress on Reproduction and Reproductive Technologies in Beef Cattle—A Review

“…Several stressors affect cattle herds. For example, heat stress affects dairy cattle [ 30 , 31 ] and beef cattle [ 14 ]. Transporting animals to the slaughterhouse or a new farm can stress them [ 32 , 33 ].…”

Changes in Cell Vitality, Phenotype, and Function of Dromedary Camel Leukocytes After Whole Blood Exposure to Heat Stress in vitro

“…Studies in different species have shown that heat stress can profoundly alter both the phenotype and function of several immune cells (45)(46)(47). Phagocytosis and production of reactive oxygen species (ROS) are key effector functions of phagocytes like neutrophils and monocytes, contributing mainly to bacterial clearance during infection (19).…”

A Retrospective Literature Evaluation of the Integration of Stress Physiology Indices, Animal Welfare and Climate Change Assessment of Livestock

“…One way to objectively assess the welfare status of an animal is through measuring if the animal is under physiological stress, which is a biological response elicited when an animal is confronted with a threat to its wellbeing [ 7 , 8 , 9 ]. The consequences of chronic, severe or ongoing stress are known to have long term implications, since for example, stress hormones, such as cortisol, can hinder immune function and thus, the effectiveness of which an individual can fight diseases and pathogens [ 8 , 9 , 10 , 11 ]. Animal Welfare has received particular attention in livestock species due to an ethical obligation to maintain a humane environment for production animals, however productivity and welfare improvements are not always parallel [ 12 , 13 ].…”