With 2008 thus far being a year of weather extremes for cattle producers, will flooding and drought affect cattle health this fall?
Watch just about any crime scene show on television nowadays and you'd think tracking down a mysterious and lethal compound is as easy as plopping a sample in a test tube and watching for the reaction you know will happen.
If only the real world was as simple as a 30-minute TV show.
But it's not, and producers in the Midwest, dealing with the after-effects of this spring's rain and floods, will likely have to do a bit more sleuthing when dealing with the potential herd health problems that nature's bounty might inflict.
“I think this could potentially be a really good mycotoxin year,” says Terry Engelken, associate professor in Iowa State University's College of Veterinary Medicine. The weather conditions this spring — flooding and a lot of rain, followed by a hot and humid summer — made for wet forage and difficult conditions to dry down hay and put up silage.
“That really allows (mycotoxins) to take off and grow,” he says. “So I think this would be a year to watch it pretty closely.”
Mycotoxins are a variety of toxic compounds produced by fungus or mold in stressed feed. In dry years, a common mycotoxin is aflatoxin in corn. In wet years, mycotoxins can be a problem in wet and moldy hay and other stored feeds.
“The real problem with mycotoxins is they can give us such a wide array of clinical signs, from very mild to sudden death and everything in between, depending on which toxin you're talking about,” Engelken says. Normally, however, producers tend to see cattle that aren't gaining like they should, cattle that just don't look healthy.
“Picture a calf that's kind of got long hair, looks kind of scruffy, is a little bit thin,” says Engelken, who was a large animal vet before becoming a veterinary professor. “That's kind of the typical picture that we have to work our way backwards from to figure out what's going on.”
That's where the CSI link comes in, says Steve Ensley, a veterinary toxicologist and section leader for toxicology at the Iowa State Veterinary Diagnostic Laboratory in Ames. “If you're looking for an unknown, it can take a lot of time and money to try to figure out if there is a risk associated with that feed.”
That's because moldy hay doesn't necessarily mean mycotoxins will be a problem. “We feed a lot of moldy hay to cows and we don't see as many problems as you'd expect, considering some of the samples we get in here,” he says. “So there's a lot of hay that has a lot of mold on it that's probably not pathogenic.”
Ensley says while veterinarians have very good analytical methods to determine if mycotoxins are present in feed, they don't yet understand how and why moldy hay can turn deadly. And with a mycotoxin test running $75-$80/sample, testing all your stored feed may be cost-prohibitive unless you and your veterinarian strongly suspect a mycotoxin problem.
But if you do suspect mycotoxins, getting an accurate test can help head off problems, particularly in your calves. Because of their larger size, mature cows can usually withstand a higher dose of mycotoxins than calves. “So on the same operation, you may not see a big affect on the mature cows, but if you're also feeding that feed to a set of replacement heifers or a set of weaned calves in a preconditioning program, we could see some issues,” Engelken says.
“And the other thing that's subtle about it, mycotoxins can have a negative effect on the immune system,” he says, and can cause reproduction issues in replacement heifers. A depressed immune system can mean greater health problems as calves head to a feedyard. “And it also means the cattle won't respond to your vaccination program as well because of the mycotoxin effects,” Engelken says.
Beyond that, Engleken says the weather this spring and summer may affect hay quality in other ways, meaning a basic feed analysis test could be helpful. “With feed prices what they are, trying to understand what the weather conditions have done to forage crops in terms of what you're putting in the shed, that's a reason to really emphasize forage testing this fall,” he says.
In addition to mycotoxins in feed, other flood-related health problems may crop up. According to Christine Navarre, Louisiana State University Extension veterinarian, Gulf State cattlemen dealt with pneumonia and other respiratory-related problems, as well as with abortions, in the aftermath of the hurricanes that smashed the region several years ago.
The cattle were highly stressed and widely scattered, she says, and with the resulting breaks in biosecurity, they became susceptible to respiratory disease challenges. “The other thing I would worry about in regard to breaks in biosecurity is you can bring bovine viral diarrhea into the herd, which can certainly give you some calf health problems.”
Although Navarre didn't see problems in Louisiana and Engelken hasn't seen any problems in Iowa, both say there are several additional health concerns that may occur as the water recedes. “One would be anthrax; another is an increase in clostridial disease,” Navarre says.
In fact, Louisiana cattlemen are battling increased clostridial problems this year, Navarre says, “and I have no way of knowing if that's a lingering effect of the hurricanes.” After getting beat up by Katrina and her cousins, Louisiana descended into severe drought. Now that rains are returning to normal, Navarre says she doesn't know if their clostridial issues are weather related or just the luck of the draw.
Then there's drought
While Midwest cattlemen were swamped with much too much of a good thing, producers in other states were dealing with not near enough. And the herd health effects of drought can be severe as well.
“It's particularly a challenge in drought because not only do we not have as much forage, but the quality of the forage is way down,” says John Maas, University of California-Davis Extension veterinarian. “And one of the important things about green forage is that it has adequate protein in it. One of the important things about dry forage is it doesn't.”
And protein drives the immune response. “Without protein, the immune response to vaccines, parasites and natural encounters with virus and bacteria is not working as well. So the dryness vs. greenness of the feed has a huge impact on the animal's immune system and therefore, herd health.”
It's particularly a problem in the calf crop. “If cows are on dry feed, the quality and quantity of that colostrum is significantly decreased,” Maas says. “So the calves don't get a very good start in terms of their immune system. They're much more susceptible to diseases like scours and respiratory disease.” And they're less responsive to vaccinations.
What's more, he says, with a compromised immune system, many of the diseases they encounter and have to fight off as young calves weaken them further down the road when they go to a feedyard. “Their lungs have been damaged, possibly their gastrointestinal tract has been damaged. So when they go to a feedlot, they're at increased risk for diseases just because they didn't get a good start. Which went back to the mom's ability to generate enough high-quality colostrum for the calf.”
Lack of protein affects reproduction as well, Maas says, and if cows have been drawing down their reserves prior to calving and breed-up, it may take years to work yourself out of the ensuing wreck.
Thus, the time-honed tactic of managing as if you're always in a drought is still valid. In addition, when dry weather does hit, think in terms of strategic supplementation, Maas says. “If you're going to have to supplement, you don't necessarily have to supplement year round.”
Most range cows in the West are used to making a living on dry forage part of the year. It's when you ask them to make a living on dry forage during critical times that problems arise.
Depending on size, mature cows should consume 1½-2 lbs. of crude protein/day during pregnancy. On green pasture, this need is easily met, Maas says. On dry range, crude protein can be 6% or less and cattle will only be capable of consuming 10-15 lbs./day, vs. 25 lbs. or more on green forage. “Thus, on dry range, you should plan on supplementing 0.6 to 1.4 lbs. of crude protein/day,” Maas suggests.
“So if you supplement them the 2½ months before they calve and get them on a good plane of nutrition then, that's the most bang for your buck. If you wait until the calf's on the ground and you're in a disaster, it's pretty hard to catch up, both on the calf health side and the reproductive side.”