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New Mexico State University

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NMSU's Clayton Researchers Study Protein in Cattle Diets

CLAYTON - Without enough protein, calves won't develop the muscle to beef up to their potential. Cattle need an ample protein supply to grow from 500 to 1,200 pounds at a feedlot.

Scientists at New Mexico State University's Clayton Livestock Research Center are trying to find optimal levels of a protein equivalent in feedlot diets. Their research is part of a large-scale study in the Southwest to examine how nutrients in feed affect both cattle and the environment.

"If you feed too much protein, you're wasting money," says Glenn Duff, Clayton superintendent. "Too much also could have an environmental impact through increased nitrogen in animal waste."

The Clayton center is part of the Consortium for Cattle Feeding and Environmental Sciences, which includes Texas A &M University Research and Extension Center in Amarillo, Texas Tech University in Lubbock, West Texas A&M University in Canyon, Texas Veterinary Diagnostic Laboratory in Amarillo, and the U. S. Department of Agriculture's Agricultural Research Service Station in Bushland, Texas.

The group is working on its first joint study, beginning with NMSU's feedlot research in Clayton. Texas Tech will do a companion study with lighter calves.

Because natural protein sources like cottonseed meal are an expensive part of the ration, feedlots use a protein equivalent called urea, which is converted to microbial protein in the animals' digestive tracts.

Cattle at Clayton are being fed diets with 11.5, 13 and 14.5 percent crude protein content, which comes from two common sources. One group's diet contains 100 percent urea, one is half urea and half cottonseed meal, and another is 100 percent cottonseed meal.

Every 28 days, the researchers work the 359 head of cattle, moving them smoothly from pens to a hydraulic squeeze chute. At the 84-day checkpoint on May 16, researchers weighed each animal and collected blood samples from three animals in each pen.

At the 84-day mark, the cattle had gained an average of 4.5 pounds per day.

"They're going to town," Duff says. He expects them to finish with average daily gains of about 3.75 pounds, similar to those at commercial feedlots.

"So far, it looks as if daily gain is increasing with higher crude protein," Duff says. "However, the relationship is more complicated than that, so the midpoint of 13 percent crude protein may turn out to be the best bet."

Researchers are also eager to see which protein source is working best.

"It's somewhat surprising that urea is outperforming a mixture of urea and natural protein sources at this point," Duff says. "It could be that urea is having a buffering effect, changing the pH levels in the rumen."

That question will provide fodder for future research.

Scientists will also work on matching nutrient levels in cattle feed with the animals' nutritional needs at different phases of growth.

"Protein levels might be stepped down as cattle get older and heavier," Duff explains. "At 500 pounds, cattle have a much higher protein requirement than at 1,200 pounds, because at that point, they're putting on more fat."

Once the cattle reach marketable weight, they will be shipped to IBP in Amarillo for processing. West Texas A&M researchers will collect information about the meat.

Environmental engineers will study waste samples from each research site to determine how feed nutrients affect nitrogen in animal waste and its potential for contamination. Because Clayton has its own small feed mill, researchers there will also do a follow-up study on processing's effect on starch availability in feed.

When completed, the two-year project will yield information for a national feed database that will help managers plan cattle diets and find ways to minimize feedlots' environment impact.

"There's a tremendous amount of interest in this research from people in the cattle feeding industry," says Mike Galyean, a researcher with Texas Tech and former Clayton superintendent.

The information will also be useful to the National Research Council, which makes recommendations for animal nutrition. The scope of the research and number of sites will strengthen the study.

"We hope this information will fill in some gaps when the database is revised in two to three years," Galyean says. "Nothing this comprehensive has been done before."