Writer: D'Lyn Ford
LAS CRUCES -- Calling all efficient cattle.
Milton Thomas, an animal scientist with New Mexico State University's Agricultural Experiment Station, wants to peek at the DNA of cattle that make the most of what they eat for good growth and reproduction.
"Because of New Mexico's grazing conditions on semiarid grasslands, we need our cattle to be efficient," said Thomas, who joined NMSU's animal and range sciences department a year ago. "We have a lot of grazing land, but we have pretty sparse grazing conditions, so we need animals that can survive and be productive in our environment."
A trait like reproductive efficiency is more difficult to select for in cattle than a trait like size that has been targeted in the past, Thomas said. "If we look at how cattle in New Mexico have evolved over the last 100 years, first they were large. Then we thought smaller would be better, and we selected for smaller cattle. Then we went the other way again, and the size of cattle went up and down."
Selecting for size was easier, because producers weighed and measured cattle and selected the biggest or smallest to continue in their breeding program. But "efficiency" isn't something that can be seen or measured so readily, Thomas said.
He is combining his knowledge of genetics and animal physiology to search for genes that make cattle better adapted to New Mexico's semiarid conditions.
"Recently, some new genes have been discovered that I think have a lot of application to this area. These genes are called feed regulatory or obesity genes," Thomas said. "Basically, what they do is control the amount of food that you eat."
When an animal gains weight, these genes -- located in fat cells -- tell the cells to make leptin, a protein. "The protein then is secreted by the fat cells, travels to the brain and tells the brain, Hey, I'm fat. I don't need to eat any more,'" Thomas explained.
In initial research, Thomas and graduate student Cleve Rasor are starting to look for the leptin gene and other genes that affect efficiency to see how much variation there is in different breeds of cattle.
"We're doing a lot of initial screening on as many animals as possible. We need to know how much variation exists, before we can start selecting the best ones for our environment," he said.
NMSU has two cattle herds that researchers are studying -- a Brangus herd at the Chihuahuan Desert Rangeland Research Center, located north of Las Cruces, and an Angus herd at the Corona Range and Livestock Research Center.
"The advantage of working with these herds is that we can bring the young animals to campus," he said. "We bring both our heifers and our bulls to campus where we can take blood samples. From the white blood cells, we can look at the DNA and then store it for years in a freezer, so we have our own DNA repository."
The researchers also keep track of the animals' production and performance over the years. "As we learn about new genes that may be important to our research, we can go back and compare the stored DNA to the production trait data we've collected," he said.
The researchers are also studying the genetics of herds at the University of Arizona and the Noble Foundation in Oklahoma, as well as a herd located in Chihuahua, Mexico.
Besides getting his research program up and running, Thomas teaches courses in beef production and animal breeding for NMSU's College of Agriculture and Home Economics.
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