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New Mexico State University

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NMSU-led research effort focuses on boosting cattle fertility

Ranchers have a lot invested by the time a cow reaches its first birthday, and the great majority of yearling heifers are successfully bred and produce a calf. But in the second and third attempts at breeding, the fertility rate drops off sharply. An upcoming research project directed by New Mexico State University scientists will examine the genetic traits of thousands of beef cattle to search for clues that can improve reproductive success.

New Mexico State University cattle geneticist Milt Thomas works with herds of Angus, Brahman and Brangus (part Brahman and part Angus) cattle.(NMSU Photo by Darrell J. Pehr)

"It's a pretty universal challenge, said Milt Thomas, a beef cattle physiology and genetics researcher in NMSU's Department of Animal and Range Sciences.

In 40 years of breeding Brangus cattle at the NMSU Chihuahuan Desert Rangeland Research Center and Campus Farm, 80 to 90 percent of the yearling heifers became pregnant by 15 months of age, in order to have their first calf by 24 months of age; however, the rebreeding rate of these first-calf heifers drops to 65 to 70 percent.

This drop in fertility is common in the U.S. beef industry. The U.S. beef industry is valued at more than $70 billion and failure of the first-calf heifer to rebreed is considered one of its largest economic drains. Therefore, even slight percentage improvements in heifer breeding and more importantly, rebreeding, rates could have ramifications valued in the billions of dollars.

In 2006, commodity receipts from agricultural products in New Mexico were about $2.5 billion, and about 74 percent of the sales were from cattle (beef and dairy). New Mexico's beef herd varies from 500,000 to 750,000 cows depending on grazing conditions. Therefore, genetic research being initiated at NMSU, which coincides with nutrition and physiology research at the Corona Range Livestock Research center, has great economic implications. The principles learned from this research also have implications for New Mexico's dairy industry.

No breed of cattle is free from the prospect of fertility problems, and cows that do not produce calves on an annual basis are usually culled from the herd. When that happens, the rancher's investment in the cow is lost, and the animal must be replaced with another young animal that also may or may not breed successfully. So how can the guesswork be eliminated?

A multidisciplinary team of scientists from NMSU, Iowa State University, Cornell University and the University of Missouri hopes to answer that question by studying the genetic pathways that regulate reproductive performance in cattle. Their findings will be used to develop gene-assisted improvement programs for fertility. The collaboration was formed from efforts of the National Beef Cattle Evaluation Consortium (NBCEC).

"We want to identify which genes, and the markers within those genes, that make some cows have an advantage over others," Thomas said. The research is being funded by a $450,000 grant from the Animal Genome section of the U.S. Department of Agriculture's National Research Initiative Competitive Grants Program.

Part of the project will be to collect data and DNA from beef cattle across a wide area of the country, with cooperating ranches in Iowa, Missouri, Nebraska, Texas, New Mexico and elsewhere. Camp Cooley Ranch, located between Dallas and Houston, which is one of the world's largest cattle seed stock producers, is allowing access to their database and DNA resources for the first part of the project. This project will be for gene and (or) genetic marker discovery and will use data and DNA from 1,000 Brangus heifers. Researchers ultimately intend to collect data from 10,000 other heifers in varied production systems and environments to implement technology transfer. Branch Ranch in Lea County, N.M., is developing a database and DNA collection system to enhance their genetic selection program. This operation will be a major player in this project and the projects that will follow in future years.

DNA samples are collected in a variety of ways, such as from blood, hair or "tissue punches" from an animal's ear. Researchers in this project will use blood cards, which require just a drop of blood placed on a special paper, and the sample can be stored at room temperature.

"It's a real cheap, cost-effective way to store lots of samples," Thomas said.

To analyze the first 1,000 samples, researchers will use the new SNP-chip technology that will provide genotypes from single nucleotide polymorphism (SNP) markers. This chip will provide 50,000 to 60,000 genotypes across the 30 bovine chromosomes. In the initial study, the technology will produce genetic data of more than 50 million genotypes. Researchers hope to identify important chromosome regions that regulate the yearling heifer pregnancy rate, then validate their findings with data and DNA from the additional 10,000 cattle. The next step in the project will be to use the same genotypes to investigate the genetic regulation of the first-calf heifer rebreeding rate. The supercomputer systems at Iowa State University will be needed to analyze the data.

The first phase of research will begin in January and continue for three to four years. The second phase of the project will focus on developing tools for Marker Assisted Selection (MAS) of genes that provide higher levels of fertility.

Another important aspect of the project is the opportunity for undergraduate and graduate students to get research experience.

"Student involvement in research greatly adds to the educational experience at New Mexico State University," Thomas said.