Transitioning cows tend to get sick more readily. But as with other stages, dairymen can improve the health and performance of the transitioning cows through better management practices. Michael Ballou, PhD presented “Systematic approach to improving immunity in periparturient dairy cows” as a recent webinar hosted by Agricultural Modeling and Training Systems in Groton, NY. Ballou serves as associate professor and associate dean for research at Texas Tech University in Lubbock, Texas College of Agricultural and Natural Resources.
“We want to know what a ‘good’ immune system looks like for a transition cow,” Ballou said as he began his presentation.
Transition cow immunology includes the immune system.
“Its primary role is to recognize self from non-self,” Ballou said. “Thereby, it protects the host from non-self microorganisms.”
He stressed the importance of knowing about the cow’s entire immune system, not just one aspect of it, to “get an idea of what’s going on because there are lots of redundancies and synergies and interactions.”
A breakdown in part of the cow’s immune system may — or may not — increase risk for disease.
“Designing an immune system is like a state-of-the art home security system,” Ballou said. “All your organs are truly important, like your wife and kids, and you want to protect them.”
To continue the analogy, he said physical barriers are like a fence around a property to prevent invasion. In cow anatomy, barriers such as skin, closed teat end, teat canal keratin and mucosal barriers prevent germs from entering the system and causing illness.
“You can’t get mastitis unless something can get inside the teat,” Ballou said.
“If a relatively small number of microorganisms infect a competent immune system can eliminate the threat without any disease,” he added.
Secondary protection includes anti-microbial secretions to ward off invading infectious agents.
“It’s not a great environment a lot of pathogens want to populate in,” Ballou said. “It’s like if you have a Rottweiler inside your front fence. If something got through that barrier, this isn’t something conducive to that pathogen.”
Macrophage provide the third layer of internal protection against pathogens.
“If someone opened your front door after getting through the fence and getting past the dogs, and they’re in your house, it’s like the macrophages signal like an alarm,” Ballou said.
Pro-inflammatory responses may seem a bad thing — after all, isn’t inflammation always negative? But Ballou said dairymen want to see the right amount of inflammatory response.
“You can also swing the pendulum too far and get too much,” he said. “Typically, I say you want enough but not a threat.”
He likened it to the right response if a thief tries to steal his barbecue grill. He might call the police, but wouldn’t request the Air Force to drop bombs on his house for the sake of excessive collateral damage.
“With inflammation, if you’re too aggressive, it can cause a lot of damage,” Ballou said.
Neutrophil represents the fourth layer, analogous to law enforcement driving around the neighborhood. Neutrophil are a type of white blood cell.
“They drive around and when they get a signal, they come to the site of the infection,” he said.
Ballou cited studies which indicate many neutrophil responses are suppressed in transition cow immunology that involve the body’s ability to fight off invading cells. He compared neutrophil in early lactation to the character Barney Fife from “The Andy Griffith Show”: dysfunctional.
According to Ballou, an ideal immune system of a transition cow should have rapid up-regulation when needed, provide a response proportional to the threat and offer rapid down-regulation once the threat is removed.
“If the tissues is infected, you want to see a response, but not an over-response,” Ballou said.
Otherwise, dairymen could cause a lot of damage with too much neutrophil present.
Looking at the mechanisms that contribute to a “Barney Fife” response during the transition period can help dairymen mitigate them. Ballou said they include stress vs. alternative pathways. While stress is natural (and sometimes desirable, as in the case of responding to threats), “Do we exaggerate the negative effects of stress regarding transition cows?” Ballou posed. “It’s likely that stress plays both an important role in the adaptation, but under certain instances increases risk for disease.”
Cows experience stress because, as creatures of habit, they dislike change. Going from non-lactating to lactating represents an abrupt and dramatic change, Ballou said.
It’s a change that’s both psychological and physiological. The cow’s interactions with both cows and humans change, along with the pen, stocking density, handling, environment, routine and more.
“I want things to be very consistent,” Ballou said.
Ballou cited studies that indicate pen moves can affect cows for up to seven days.
“Dry matter intake also decreased when a single cow was introduced to a stable group of 11 cows,” he said. “Dominant lactating cows did not change behavior, but intermediate and subordinate cows produce less after a pen move.”
Overstocking, reducing feed bunk space, and increasing stocking density create an opportunity for competition, for winners and losers. But “winners” may not win after all.
“Dominant cows were more likely to have a uterine disease and be culled from the herd,” Ballou said.
He explained that, sometimes, bossy cows spend so much time dominating other cows that they don’t get enough rest and feeding time themselves. That lowers their production.
Providing the stocking density is low enough, the meeker cows still get enough to eat and perhaps even more than dominant cows because they simply go elsewhere while the herd’s boss rushes off to bully another cow.
Physiological stress includes the animal’s need for more nutrients and increased nutrition. Unfortunately, cows may not readily present signs they’re ill.
“Animals are really good at hiding disease,” Ballou said. “That became apparent to me.”
As a researcher, he measures traits in blood and tissues. Once he observes clinical signs of disease, it becomes much more difficult to return the animal to good health — costing the farmer time and money, along with causing the animal unnecessary suffering. That’s why preventing health issues through better management has become so much more important.