Dysregulation of the immune system occurs during critical phases of production such as the transitioning period. Good animal husbandry, which includes attention to nutrition, minimizing the exposure of cattle to multiple concurrent stressors, and attention to biosecurity, can improve both innate and adaptive immune functions.
“Some people overlook these not very ‘sexy’ strategies in their ongoing search for the latest silver bullet that can protect cattle from all disease, all the time, regardless of inadequate management,” say Amelia Woolums, DVM, PhD, Dipl. ACVIM, Dipl. ACVM, University of Georgia. “Nutritional deficiency and prolonged stress have both been shown to impair innate immune functions as well as adaptive immune functions, so preventing these problems is important to support both arms of the immune response.”
It’s interesting, Woolums says, that short-term stress can actually improve innate immune responses. A recent study showed that neutrophil function in bulls increased over baseline at 48 hours after a short (four hour) transport (Hulbert et al, Vet Immunol Immunopathol 2011; 143:66-74). “So from the perspective of the immune response, not all stress is bad,” she adds. “Persistent or chronic stress is generally a problem, but short-term stress is not always a problem.”
Proper nutrition is needed for all aspects of performance and the immune system is a key homeostatic mechanism to keep the body healthy, says Marcus Kehrli, Jr., DVM, PhD, National Animal Disease Center, Ames, Iowa. “Simply put, in the absence of proper nutrition, the immune system will not perform optimally. However, very little research has been done to define basic nutritional requirements of cattle to support immune function; especially lacking is science defining the nutrient requirements of transition cows.”
Because nutritional deficiency can impair innate immune responses, some believe that supplementing nutrients (such as vitamins or minerals) in excess can improve response. Woolums says numerous studies have looked at the impact of various nutrients and feed supplements on immune response, and the bottom line is that nutrient supplementation in excess of maintenance requirements does not consistently improve immunity, although there are specific examples of certain vitamins or minerals associated with improved immunity.
Regarding vaccines, Woolums says it’s interesting to note that adjuvants, which are often included in vaccines to improve the host immune response, likely work at least in part by activating the innate immune response. “For example, it’s been shown that alum, which is an adjuvant commonly used in human and veterinary vaccines, interacts with receptors inside of cells which activate innate immune pathways, and this interaction is what leads to the adjuvant effect induced by alum.”
“Immunologists recognize that we can enhance selected aspects of innate immunity but there might be risks associated with doing this in healthy animals with normal functioning immune systems,” Kehrli says. “You can certainly have too much of a good thing. However, use of immune modulators is a viable approach to restoring a derailed immune system back to normal and ideally this should be achieved without causing any damage to the host through an over-exuberant immune system.”