Weaning Stress and Nutritional Influences

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Originally published on TheHorse.com

One of the most stressful times in a horse's life is weaning, when a foal is separated from his dam and asked to adjust to life on his own. But according to Amanda Adams, PhD, a postdoctoral scholar at the University of Kentucky's Gluck Equine Research Center, certain types of nutritional support could reduce the stresses and health challenges that weaning places on young horses. She spoke on the topic at the 2011 Alltech International Animal Health and Nutrition Industry Symposium, held May 22-25 in Lexington, Ky.

"Weaning is probably the most stressful event in the horse's life because they go through maternal separation, environmental changes, diet changes, and management changes," Adams explained, adding that weaning poses a number of physiological challenges on young horses, including:

• Increased heart rate;
• Decreased daily weight gain;
• Increased cortisol (the stress hormone) secretions; and
• Increased susceptibility to respiratory disease (e.g., pneumonia caused by Streptococcus zooepidemicus, Rhodococcus equi, equine herpesvirus-1) and gastrointestinal infections (e.g., diarrhea and Lawsonia intracellularis infections).

Why is this? According to Adams, this is a complex question with no simple answer.

She explained that these challenges could be caused by a decrease in the weanling's immune system response. With a team from the Gluck Center, Adams observed that after weaning (21 days), and possibly due to the physical and mental stress of the experience, foals' immune responses decreased, potentially leaving them at risk for health problems. The weanlings' immune responses were eventually observed to returned to normal, but Adams stated that minimizing weaning-associated stress might help prevent decreased immunity post-weaning.

Adams relayed that a large portion of the horse's immune system is located in the gut and researchers acknowledge that the region's microbiota can influence this mucosal immunity. Thus, she explained that keeping the gastrointestinal tract healthy could potentially help modulate the immune system and in turn keep the animal healthy. Adams discussed a few ways she believes could potentially modulate foals' immune systems:

• Pre-weaning, she suggests providing the foal with a good-quality creep feed, as greater weight gain could lead to increased immune function;
• Adding probiotics to the foal's diet has been noted to increase immune function in cattle and pigs during weaning, Adams explained. She feels she supplement might also help stimulate the weanling's cell-mediated immunity, in particular interferon-gamma production, which is an important molecule that helps protect the animal from some infectious diseases; She noted that more research is needed to confirm this hypothesis; and
• Adding yeast to the foal's creep feed prior to weaning could help modulate the immune system when the foal is weaned, she suggested.

"It's all about balancing the immune system," she said.

Adams noted that more research is needed to fully understand how weaning affects all arms of the immune system and how horse owners can reduce young horses' stress and improve immune function prior to and during weaning, which could ultimately lead to decreased susceptibility to infectious disease during this time.

But in the meantime, she said, nutritional support for the weanling's immune system could potentially make weaning a healthier time for the foal. It is advisable to work with a veterinarian or an equine nutritionist to develop a feeding program for each individual foal to provide optimal nutritional support.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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