While you may disagree with the terminology or long-term influence, it is true the climate is changing. The summers are hotter and weather extremes are more evident. Climate change is a factor in livestock production, and Dr. Veerasamy Sejian says it’s important for producers to understand – and adjust to – its impact.

Sejian is from India’s ICAR-National Institute of Animal Nutrition and Physiology. He and his colleagues reviewed the latest research on the effects of heat stress on livestock immunity, and reported on it in Pertanika Journal of Tropical Agricultural Science. They discovered that livestock immune functions are either suppressed or enhanced, depending on the length of exposure to heat stress.  

“Heat stress mainly affects the immune system through three endocrine glands: the hypothalamus and pituitary glands located in the brain, and the adrenal glands located above the kidneys,” Sejian said. “Activation of the hypothalamo-pituitary-adrenal axis leads to the secretion of hormones that affect various components of the immune system.”

He noted that stress also impacts the system responsible for what is known as the “flight-or-fright” response.

“This system, called the sympathetic-adrenal-medullary system, acts by releasing chemicals that enhance the breakdown of glycogen, increasing blood glucose levels so the body can meet its higher stress-induced energy requirements,” Sejian said.

Generally, activation of these two systems alters animals’ immune functions, affecting the integrity of protective barriers and the response of immune cells to attacking pathogens, according to Sejian.

Life Cycle Also Affected
Heat stress also impacts critical events in the life cycle of livestock, including the passive transfer of maternal antibodies to offspring via milk and developing an effective response to vaccination, the researcher said.

“Effective management of animal shelters and providing evaporative cooling systems can play an important role in reducing the effects of heat on livestock,” Sejian said. “Rearing livestock that are selected for their heat-tolerant genes can also form an effective protective strategy.”

Recent research has shown that modifying animal nutrition can be an effective approach to heat-stress management.

“Vitamin A and zinc supplements, for example, can help maintain protective barriers against pathogens in the gut and udders,” Sejian pointed out. “Combined supplements of selenium and vitamin E can positively influence the ability of white blood cells to attack pathogens. Iron can also play an important role in promoting the development of immune-related glands.

He noted that another important protective strategy involves the naturally-occurring bacteria present in the animal’s gut.

“Prebiotics are ingestible ingredients that stimulate the growth and activity of gut bacteria. When gut bacteria are healthy, they compete against invading bacteria for food, preventing the invaders from flourishing,” Sejian said. “Probiotics are mixtures of live microorganisms that are beneficial to animal health. These line the gut, strengthening its mechanical barrier. They also compete with pathogenic bacteria, making it more difficult for them to survive.”

The team’s review could serve as useful reference material for researchers studying livestock production in a changing climate scenario by means of optimizing livestock immune systems. The full paper is available here: http://bit.ly/2fJbunT

For more information about this research, contact Dr. Sejian: drseijian@gmail.com