­Providing proper nutrition and minimizing stress can improve a cow’s ability to fight disease.

Pump up your cows' immunityWhile good animal husbandry is not very sexy and some people overlook it in their ongoing search for a “silver bullet,” it is vitally important, points out Amelia Woolums, professor of large animal internal medicine at the University of Georgia.

“Nutritional deficiency and prolonged stress have both been shown to impair (the cow’s) innate immune functions as well as adaptive immune functions,” so preventing these problems is important to support immune response, she says.

Enhanced immunity is a collective effort between you and the cow, and that includes judicious use of nutritional supplements and animal health products.

Proper nutrition

“In the absence of proper nutrition, the immune system will not perform optimally,” says Marcus Kehrli, Jr., veterinary medical officer at the National Animal Disease Center in Ames, Iowa.

“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,” he says.

The transition cow is faced with numerous challenges. For example, hypocalcemia during the transition period has been associated with depressed neutrophil (immune cell) function.

Epidemiological data going back decades have identified greater disease incidence in transition cows that experience ketosis and/or milk fever. “Given the immune system requires a wide array of nutrients… it only makes common sense that if we short-change the transition cow nutritionally, it will only further enhance her susceptibility to a myriad of infectious diseases, particularly in the first few weeks of lactation,” Kehrli says.

Some believe that supplementing nutrients, such as vitamins or minerals, in excess can improve response.

Yet, numerous studies have looked at the impact of various nutrients and feed supplements on immune response, Woolums says, and the bottom line is that nutrient supplementation in excess of maintenance requirements generally does not improve immunity, although there are specific examples of certain vitamins or minerals associated with improved immunity. For example, vitamin E and selenium have been shown to help defend against mastitis.

It’s important to have the animals as stress-free as possible, since stress releases cortisol which can interfere with immunity.

Antibiotics and vaccines

Antibiotics have significantly lowered mortality rates of many bacterial diseases, suggesting that antibiotics fill a void when the cow’s innate and adaptive immunity fails to optimally protect against mortality.

“Furthermore, some classes of antibiotics are known to accumulate inside phagocytic cells of the innate immune system and, in so doing, help the phagocytic cell more efficiently kill an ingested bacteria,” Kehrli explains.

However, the cow’s innate immune response is also critical for antibiotics to be useful as evidenced by the fact that animals with defects in innate immune function, such as defects in neutrophil function, develop repeated bacterial infections that cannot be effectively controlled long-term with antibiotics. “So, I would say that antibiotics and the innate immune system work hand-in-hand to fight off bacterial infection,” Woolums says.

Kehrli adds, “We already know quite a bit about the effects of various physiological stressors on neutrophil and lymphocyte functional activities, as well as the reduced ability of an immune-suppressed animal to respond to vaccination.

“However, we don’t know all of the underlying causes of poor responses to vaccines,” he adds. “Hence, it is critical that we invest in research to provide a better understanding of which components of the innate immune system are necessary for effective vaccine responses.” (See “Get the most out of vaccines” on page 24 of the February issue of Dairy Herd Management.)

Geni Wren is editor of Bovine Veterinarian, a sister publication of Dairy Herd Management. Portions of this article appeared in the July-August issue of her magazine.


Get the most out of vaccines

When Vic Cortese goes out to a farm, he makes it a point to check the farm’s refrigerator.

“A majority of the time, the refrigerator is set either too cold or too warm,” he says, adding that he actually measures this with a thermometer. He would like to see the temperature around 40 degrees F to optimize performance of the vaccines stored there.

And, he says, he would rather see the vaccines stored on the shelves of the refrigerator rather than the door. Not only do the vaccines get jostled on the door when the door opens and closes, they are also subjected to greater temperature extremes since the door is the first place receiving warm air when the refrigerator is opened.

“It’s amazing how much dairies pay for (the vaccines) and then place them in an old refrigerator that got taken out of the house that doesn’t maintain temperatures correctly,” says Cortese, who serves as director of the Veterinary Specialties Group at Pfizer Animal Health.

Some other things to be aware of:

• Modified-live vaccines can begin to lose potency once they are mixed, so be sure to use them promptly — within 45 minutes to a few hours, depending on the product and situation. Consult with your veterinarian on proper handling and administration techniques.

• Some of the harsher disinfectants, when used to clean syringes, can kill a vaccine if the residue hasn’t been removed. Ultraviolet light from direct sunlight can have the same effect.

• Unless it’s stated on the label that “duration of immunity studies have been established” for a vaccine, it’s unknown exactly how long a vaccine will protect an animal. Many times, the vaccine label will simply take a default position and recommend “annual re-vaccination.” But that can be misleading, because producers might look at “annual revaccination” and think that one shot is all that is needed when, in fact, a booster is often needed as well. Again, consult with your veterinarian.

• It’s important to understand antibody interference with vaccines. Antibodies that are already in the animal from colostrum or a previous vaccination can bind to the agents in a vaccine known as antigens, which basically tells the rest of the immune system that “everything is already taken care of, so don’t worry about it.” It’s like flipping an off-switch at a time when the animal needs extra protection. This is a problem with some diseases more than others — BVD is an example where existing antibodies can block a vaccine. Your veterinarian is an important resource for letting you know when to time the vaccines.