Research links brisket disease with cow size

Colorado Springs, Colo. – As cow size continues to increase, cattle may be outgrowing their organs, according to a cattle specialist from Oklahoma State University and a veterinarian from Colorado State University.

The two addressed cattle producers during a Commercial Cattlemen’s Symposium held during the National Red Angus convention in Colorado Springs, Colo.

David Lalman of Oklahoma State University discussed the controversial topic of ideal cow size and efficiency. Lalman told a packed room of producers that when it comes to size, “It is a never-ending arms race for growth in the cattle industry.”

“At some point, we will have to determine when it’s enough,” he says.

Increasing size

Within the next 10 years, Lalman thinks the industry will moderate its rate of growth regarding cow size.

“I think, as a producer, we have to ask ourselves, what good does continued selection for growth do for my cowherd at home?” he said.

Referring to industry data, finished cattle weights are continuing to increase at 9.4 pounds a year. However, with that increase comes better quality, he notes.

“Almost 80 percent of the cattle grade Choice now, but I think the incentives for cattle grading Prime will continue to drive the industry to produce even better cattle,” he adds.

Cutability has declined, which means the lower the yield grade, the leaner the cattle, Lalman says, adding “We are seeing fewer cattle grade one or two, and more cattle are yield grade three now.”

Trait selection

In the beef cowherd, Lalman tells producers that the number of exposed cows that wean a calf hasn’t significantly changed since 1991.

Cattle in the Southern Plains naturally have lower fertility because of heat stress, more parasites and less fertile Bos indicus influence, he says, asking what about in other areas?

“Commercial cowherd fertility has made little to no improvement, except for dystocia,” he notes, adding it is an area where more research is needed.

Lalman also addressed the beef industry’s direction in selecting cattle for milk production, stating the average commercial cow produced 12 pounds of milk in 1984, according to data from the National Research Council. By 2016, that number had climbed to more than 20 pounds.

Research conducted at Oklahoma State University found that number closer to 31 pounds at peak yield in commercial Angus cows, Lalman says. The more milk produced by the cow, the higher her year-around maintenance requirements will be, he continues.

Increased maintenance requirements are also related to an increase in visceral organ mass, he says.

Link to brisket disease

Tim Holt, a veterinarian at Colorado State University, explains how cow size is increasing faster than visceral organ mass, which contributes to brisket disease in cattle living at higher elevations.

“At high elevations, there is less oxygen available for us to breathe, so our respiratory rate increases to compensate,” he explains. “If we come to higher elevations, we become hypoxic, and shunting of the blood vessels will occur.”

At high elevation, blood is pushed from the bottom of the lungs to the top of the lungs, when there is more oxygen.

“In cattle, the blood vessels get smaller in higher altitudes, which causes the vessels in the body to shut down. When the vessels close off, blood can’t get to the lungs, which is called vasoconstriction,” Holt explains. “It makes the heart rate pick up, and since the blood has nowhere to go, the animal gets brisket or high altitude disease.”

“When the heart is pounding, the animal can go into congestive heart failure and die,” he continues. “It is a heritable trait based on the animal being hypoxic.”

“That is why we do pulmonary arterial pressure (PAP) testing in cattle that are above 5,000 to 6,000 feet,” he explains.

Testing bulls

PAP testing is key for cattle producers who raise bulls in high altitude areas.

Since brisket disease can be a hereditary condition, Holt recommends producers only sell bulls with low PAP scores.

“Only two other species get high altitude disease – swine and poultry,” he continues. “Poultry get it because the industry bred for bigger birds that outgrew their heart and lungs.”

When Holt started PAP testing cattle in 1979, the disease occurred in cattle at 7,000 feet or above, but since then, he is seeing it at lower elevations.

“A lot of cattle die within weeks before being slaughtered,” he says. “We are genetically building animals that are outgrowing their cardiovascular systems.”

“We need to select animals with bigger lungs and hearts to withstand higher altitudes,” he explains.

Gayle Smith is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.