Armed With Immunity

July 3, 2018 11:33 AM
 
You can select, breed and feed for a healthier herd.

When managing a dairy, there are a few indisputable, intertwined facts as it relates to the health of your herd.

First, healthy cows make more milk. That makes sense, healthy cows would certainly milk more than sick cows.

Second, healthy cows are more profitable. That makes sense, too, because healthy cows don’t need medicines or vet care to fix problems.

As a result, healthy cows milk more and are more profitable, so they stay in the herd longer. Again, a no brainer. Longevity is important for a number of reasons. Mature cows generally milk more than first lactation heifers. Cows that last longer make for a larger lactating herd that creates greater flexibility with managing replacements and herd inventory. And cows that last longer are just good for animal welfare.

So if healthy cows are so important, let’s develop cows that are less likely to get sick, then manage them in a way that builds immunity throughout their productive life.

It’s The Immune System

The core to a healthy animal is a healthy immune system. That’s the part of the body that no one sees but is instrumental at warding off disease. No one sees it because it’s really a network of cells, tissues and organs that work together to protect the body.

“Every organ in the body has an immune function,” says Elliot Block, research fellow with Arm & Hammer Animal and Food Production. “But then those organs talk to each other to create a defense system.”

Like the National Guard, the immune system is always there, ready to fight off disease or anything that could harm the body, but it’s not always on active duty.

“You want an immune system that is resilient, one that is going to respond to all of these disease insults and then bounce back,” Block says.

Because the immune system is more of a network than an organ, it’s difficult to say how to improve the system, or what impact it even has on productivity. Take fresh cow problems, for example. Cows at calving are more susceptible to diseases and disorders because they’ve just been through a traumatic experience during the days leading up to calving, the actual calving experience and the hours and days of recovery. That’s probably a time when the immune system is needed the most.

“I think things like retained placentas and metritis are being warded off so now the immune system is allowed to do what it wants to do and function,” Block says. “It’s not that the immune system causes the cow directly to make more milk. But she’s fighting off more of the subclinical infections and she’s able to repair herself more quickly.” The result, Block says, is a cow that feels better, eats better, drinks better and therefore makes more milk.

If the immune system is a hard-to-see network of cells and organs, then improving the immune system would seem to be a difficult task. Perhaps a place to start is through genetics, creating an animal that is better at fending off disease.

Start With Genetics

Trying to reduce the incidence of health problems is a relatively new option for dairy producers. In the past, selecting for health traits has been reactive rather than proactive.

“You can select after the fact based on what happened when a cow had health problems, and we’ve done mostly that in this industry,” says Kent Weigel, professor and chair of the dairy science department at the University of Wisconsin. “The good part is that health problems tend to be positively correlated with each other, so if you select for an animal that can deliver less mastitis or metritis, for example, then you are probably not going to get more DA’s or other disorders.”

If you want to breed for a healthier herd, AI companies offer sires that are better at improving traits related to several fresh cow disorders. Some of those traits carry high enough heritabilities to effect change in the herd. On the female side, genomic tests offer the opportunity to select animals based on a set of wellness traits. Over time, identifying the right females and breeding them to the right bulls could help improve the health of your herd. That should mean that immune function is improving as well.

“Over time you will cull the cows with poor immunity because they got sick,” Weigel explains. “And you would hope the reverse is true as well. You have selected animals based on some immune system function that leads to fewer health problems.”

For decades we’ve been selecting for better health traits, sort of.

“We’ve had [a] productive life [trait] for quite a long time and that does a decent job,” Weigel says. “Now we’re just getting more specific.”

Ultimately, what producers are really after is the cow you never notice.

“We literally just found a nine-year-old cow that came up with a right DA and we’re like, where have you been?” says Garrett Luthens, manager at Skyview Dairy, a 1,400-cow herd near Hutchinson, Minn. “We never knew she existed because she has never had mastitis, she calves back literally every 12½ months and just now she’s coming through our system.”

Even at nine years old, Luthens elected to do the DA surgery because she’s more than paid her bills over her lifetime.

“Probably 75% of our herd is that way, we just get fixated on the other 25% because you know their names and everything that’s been wrong with them,” Luthens says.

He thinks there has to be genetic differences between cows with regard to their ability to avoid getting sick.

“You’ll have one cow that calves in overweight, they’re always dirty and yet they never get sick,” Luthens says. “Then you’ll have a pristine cow who you pretty much put in bubble wrap and she still gets sick.”

Genomics aside, Luthens says a big part of their farm getting to a pregnancy rate of 35% and higher starts with healthy cows.

“That’s pretty much the No. 1 factor,” he says.

If you have selected and bred for animals that can withstand disease incidents, you probably have a good foundation for building immunity in your herd. But there are ways, nutritionally, to support immune function.

Remember, supporting immune function is not the same as stimulating the immune system. Supporting immune function means you’re keeping the army fed and ready to respond. Stimulating means you’re putting them into action.

“You never want to stimulate the immune system for the sake of it because the immune system is probably one of the largest, if not the largest, energy drains on the cow,” Block says. “So to stimulate it could mean robbing nutrients unnecessarily for productive purposes. You just want it primed and ready to go.”

Proper Nutrition Can Help

“Obviously, we know that when you have undernourished cows the immune system doesn’t work well,” Block says. “It’s because the immune system is using the same nutrients that every other tissue and organ in the body is using.”

According to Block, focusing on amino acid and energy balance is significant, as is providing adequate vitamins and minerals.

“Probably the three most significant nutrients that work in the immune system are vitamins, minerals and essential fatty acids,” Block says. “Those are used directly by the immune system because without them it doesn’t function.”

The immune system uses protein and energy as fuel, but those three ingredients are critical.

“Without all the little co-factors, vitamins and essential fatty acids to make prostaglandins—those are the heart of the immune system and what keeps it ready to spring into action,” he says.

As producers dredge through this milk price downturn, Block is concerned some have taken out ingredients that support immune function because of cost. Something, he says, that could have a longer term impact on health and reproduction.

“In those herds that have made that decision, the reason disease incidence is up and reproduction is down and they have more cows in the sick pen, that’s all due to the immune system,” he says.

And what about the aforementioned cow that never seems to get sick?

“I’m going to attribute that to genetics,” Block says.

Because if all of the cows in a group are exposed to the same disease factors, why does the one cow not get sick?

“It’s got to be because her innate immune system is more functional,” he says.

Creating a whole herd of cows like that should be the goal of any producer. Technology allows us to select for and breed toward these individuals, and sound nutrition programs help them stay that way.

 

Note: This story appears in the July issue of Dairy Herd Management

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