Stress and its Negative Impact on Dairy Cows,
On a daily basis, dairy cows can experience stress. Stressful things in their lives include, but are not limited to, weaning calves1,2, transitioning3 from dry to lactating, heat and other environmental issues4,5, and physiologic problems, like ruminal acidosis6,7,8. When the cumulative amount of stress gets too high, then feed intake goes down causing health and performance issues to increase. One important physical consequence of too much stress is a harmful change in the permeability, or leakiness, of the small intestine. In truth, any event that causes a reduction in feed intake can have a negative impact on intestinal permeability,9,10,11 leading to a cascade of physiological responses that divert energy and other resources away from the udder and its normal production of milk. The rumen and small intestine are structured to allow nutrients to pass through while providing a barrier to harmful substances, specifically pathogens and food particles that can cause a costly inflammatory response. In short, any breakdown in this important barrier function, that is to say, an increase in leakiness, can have significant negative repercussions.
Compromised intestinal integrity (increased permeability) can cause:
- A decrease in nutrient absorption across the intestine and a dangerous movement of potentially harmful materials, like antigens, into the blood.
- Damage to intestinal tissue and the presence of antigens, like lipopolysaccharides (LPS), which activate the immune system.
- Use of >2 kg glucose/day14 by an activated immune system; energy that should be used for production.
- Reduced birth weights, followed by reduced pre-weaning growth rates15.
- Impaired immune function in neonates.
- Reduced passive immunity (lower serum IgG concentrations).
- Reduced growth and absence of cells responsible for innate immunity.
- Decreased milk production in fresh heifers.