Research paves the way for improved animal health and productivity

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Nov 11, 2008

Research paves the way for improved animal health and productivity

“One objective of the study is to determine the genetic variation in feed efficiency among individuals.”

The Agricultural Re search Service’s (ARS) ge nomics and phenomics re search is laying the founda tion for future livestock production improvements. Understanding how inher ited characteristics relate to specific genomes will eventually allow research ers to develop tools that can be used to guide animal breeding, selection, and management decisions.

Throughout the U.S., ongo ing ARS research projects are changing the way in dustry members breed, raise, and produce our na tion’s most valuable agri cultural animals.

Identifying DNA markers and traits

ARS scientists at Clay Center, NE, and Miles City, MT, joined an international consortium in sequencing the bovine genome in 2002. Today, ARS scientists throughout the country are using this information to improve beef cattle man agement and production.

Some ARS researchers are using genomic research to improve animal health. This is particularly useful in situations with infected but asymptomatic cattle, says Mohammad Koohm araie, former director of the Roman L. Hruska U.S. Meat Animal Research Center (USMARC) at Clay Center. For example, cattle can carry diseases like bo vine respiratory disease (BRD) without having symptoms. This compli cates attempts to assess their genetic resistance.

Having ways to identify asymptomatic cattle or those at higher risk of ill ness would allow scientists to more accurately gauge how genes affect resistance.

To improve their assess ments, USMARC research ers led by geneticist Larry Kuehn are working with scientists at the ARS Na tional Animal Disease Cen ter in Ames, IA, to develop large collections of cattle phenotypes, or observable traits. These include traits such as general immune system functionality, body temperature, respiratory rate, and feeding behavior.

The phenotypes will be drawn from populations representing prominent breeds in the U.S. beef in dustry. 

“By examining a larger group of traits, we can more accurately classify animals into categories according to their potential disease risk or res resilience,” Koohmaraie says. This will enable re- search searchers to identify traits that aare most indicative of poten potential BRD risk and de- termi termine how those traits relate to genetic resistance to it. One tool that could help scient scientists in this and other projec projects is the Illumina Bo- vine SSNP50 BeadChip—a glass gglass slide containing thou- sand ssands of DNA markers ccalled ll d “single nucleotide ppolymorphisms,” or SNPs, wwhich are used to find rela- ttionships between DNA mmarkers and traits of econnomic importance.

The BeadChip B has re- search ssearch ap applications for both beef and dairy cattle. Design was led by ARS re searchers at Beltsville, MD, in collaboration with scien tists at Clay Center, the University of Missouri, and the University of Alberta in Canada. The chip is being used at all those locations aand many others—a total oof at least 23 locations in 11 ccountries.

A single chip generates aabout 53,000 genotypes for each of 12 individual ani mals. DNA samples from the animals are applied to the BeadChip, chemically labeled, and scanned to produce genotypes. Statis tical analyses of genotypes can identify relationships between DNA markers and economically relevant pro duction traits.

“Genomic tools like the 50K SNP chip will provide the greatest opportunity to transfer our genomic dis coveries in a usable form to the industry,” Koohmaraie says.

Beef cattle: Fat and feed efficiency

One project using the BeadChip technology is a USMARC investigation into the influence of genetics on feed efficiency. Research leader Cal Ferrell, geneticist Mark Allan, and their col leagues are identifying phe notypes that relate to postweaning feed efficiency and lifetime productivity in beef cattle.

“One objective of the study is to determine the genetic variation in feed efficiency among individuals and breeds using quantitative and genomic technologies,” Ferrell says. The research ers are also using the geno types generated from the chip to find relationships between DNA markers and phenotypes that can be used to enhance genetic selection in beef cattle.

“These studies could lead to development of genomic tools that could enhance the accuracy of breeding and management decisions,” Al lan says. “Genetic markers provide opportunities to im prove selection for traits that are difficult to measure in an industry setting.”

ARS scientists are also using genomic research to improve beef cattle produc tion at the Fort Keogh Live stock and Range Research Laboratory in Miles City. There, they have identified genetically significant areas called “quantitative trait loci” (QTLs) related to pro duction traits such as beef quality and composition, feed efficiency, and repro ductive success.

“Our work has led us to loci with significant effects on beef quality and compo sition which have potential implications for human health,” says geneticist Mike MacNeil. MacNeil, geneticist Lee Alexander, and physiologist Tom Geary have collaborated with US- MARC geneticist Warren Snelling to analyze whole genome scans of 328 cattle bred by crossing Wagyu and Limousin parents.

Wagyu is a Japanese breed with substantially more marbling than the more muscular French breed, Limousin. In all, the team has identi fied seven QTLs related to tenderness, palatability, and fat composition. They found a region on chromosome 2 that influences the concen tration of monounsaturated fat—believed to be healthier than saturated fat—in beef. With further research, in collaboration with USMARC chemist Tim Smith, they hope to develop genetic markers associated with the variation in this trait. That could ultimately lead to identification of the gene or genes responsible and allow for marker-assisted selec tion in other cattle breeds to alter the fatty acid content of the meat. — WLJ

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