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Transition cow: Focus on immune response

Transition cow: Focus on immune response

RESEARCH has established that transition cows are more susceptible to disease and reduced productivity — a result of the stressors associated with calving and lactation.

Therefore, improving transition cow health should focus on strategies for reinforcing the cow's innate immune system while also limiting environmental and management stressors, according to Dr. Michael Ballou, a nutritional immunologist with the department of animal and food sciences at Texas Tech University.

Speaking at the recent Central Plains Dairy Expo in Sioux Falls, S.D., Ballou noted that the risk of mastitis and metritis is greatest during the early lactation period, primarily due to environmental microorganisms. However, he said a competent immune system can eliminate the threat of disease from many known microorganisms of importance to the dairy industry.

"It is often said that the immune system of a transition cow is suppressed," Ballou said. "This is partially correct but may be an oversimplification. I prefer to say the immune system of a transition cow is temporarily dysfunctional."

He cited research showing a variation in immunologic function among and within cow groups in the same dairy, reinforcing the importance of obtaining a better understanding of what is contributing to that variation and how to identify and improve the health of "at-risk" cows.

Ballou said cows are creatures of habit, and the switch from non-lactating to lactating — combined with the physiological impact of high nutrient demand associated with lactation — places abrupt, dramatic stress on their immune defensive function.

To improve transition health, he recommended:

* Nutritional strategies to support the cow's immunological function, as well as antioxidants and acidogenic diets.

* Reduction of the cow's pro-inflammatory response through nutrition, pharmaceutical drugs and vaccines.

* Management practices that promote cow comfort and limit additional stressors, including maintaining a clean, dry environment, keeping cows cool or warm, avoiding overcrowding, limiting pen moves, providing fresh, palatable feed and keeping fresh cows locked up for less than an hour.


Heifer mastitis

Managing mastitis is most commonly focused on lactating cows, but the prevalence of mastitis in unbred, breeding age and pregnant dairy heifers is higher than formerly realized, according to Dr. Stephen Nickerson, a professor of lactation physiology at the University of Georgia.

While antibiotic infusion products have been used successfully to cure existing infections, Nickerson said the goal should be to prevent new infections from occurring in these young dairy heifers through management strategies that include not only vaccinations, use of teat seals and fly control but also dietary supplementation.

At the Southwest Nutrition & Management Conference in February, Nickerson noted that dietary supplementation to boost the immune systems of heifers has been shown to reduce the incidence of mastitis at calving.

"Heifers may carry intramammary infections for a year or more before they are diagnosed with mastitis," he reported. "The greatest development of milk-producing tissue in the udder occurs during the first pregnancy, so it is important to protect the heifer mammary gland from pathogenic microorganisms to ensure maximum milk production during the first and future lactations."

He said diet plays a role in udder resistance to infection because certain nutrients affect various mammary resistance mechanisms.

Nickerson participated in a 2011 study submitted to the Journal of Dairy Science in which 40 dairy heifers, beginning at five months of age, were fed a daily supplement containing a specific additive (OmniGen-AF).

Overall, postpartum results showed that these heifers exhibited increased milk production, a decreased prevalence of mastitis and lower somatic cell counts, suggesting a positive effect on the immune system compared to control heifers that did not receive the supplement, he reported.


Ground corn

What if corn supplies could be stretched a bit further or milk production increased just by re-evaluating how finely corn is ground?

Dr. Dave LaCount, a dairy nutritionist with Purina Animal Nutrition, said if corn is not ground properly, a dairy herd could be losing milk performance potential.

"It is imperative that corn is adequately ground in order to ensure adequate energy availabilities and full utilization of corn," LaCount said.

Research shows that when evaluating cracked versus ground corn, there is up to a 6.1 lb. milk production advantage to feeding finely ground corn over cracked corn.

The response on the farm will be dependent on how coarsely the corn being fed is. On-farm responses to grinding corn more finely are commonly 3-5 lb. of milk.

Whether corn is purchased from a vendor or grown on the farm, producers need to make sure it is ground finely enough prior to feeding it to cows.

When evaluating corn, the goal is an optimum average particle size of 750-850 microns, LaCount said, noting that "microns or particle size of the corn can easily be measured on the farm."

"Any corn below 22% moisture should be 600-700 microns," LaCount noted. Samples of ground corn can also be submitted to a laboratory for more precise evaluation.


Nitrogen uptake

Research is attempting to balance more efficient uptake during cows' digestion of nitrogen feed fertilizer to help reduce the level of cattle flatulence responsible for generating methane, a greenhouse gas.

The amount of nitrogen that is excreted by livestock is directly proportional to the amount that is fed, according to Chris Reynolds, who conducts nutritional physiology research with ruminants at the University of Reading in the U.K.

He is a principal investigator on one of the work groups of the REDNEX project, which is scheduled to reach completion this year. Funded by the European Union, the project investigated ways to reduce the excretion of nitrogen by dairy animals.

"Our aim was to look at management approaches so that we can reduce the amount of nitrogen we are feeding the animals," Reynolds said.

An important component of the project was to ensure that the reduced amount of nitrogen intake would not cause a loss in milk production. Therefore, the research focused on improving the efficiency of cows' nitrogen uptake, Reynolds explained.

"We improved the understanding of the effects of lower-nitrogen diets on the metabolism of cows, and we demonstrated that we could feed such diets without substantial losses of protein," he added.

However, the researchers were surprised to discover that reducing nitrogen in forages could have a negative effect on the environment, finding that it increased the production of methane in their flatulence.

"If you use less nitrogen fertilizer, you may produce forages that are less digestible and, therefore, have a higher methane yield," Reynolds said. "We have to focus on a whole-systems approach."

This complication requires further research, he added.

"There are not many options to reduce nitrogen emissions, and this is one of the projects that appears to be promising," noted Peter Wizke, a researcher in economic and agricultural policy at the University of Bonn in Germany.

Volume:85 Issue:19

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