3 May 2012

5 minute read

North America

Improving the genetics of livestock is a continual aim for producers. US - Genomics (DNA testing) is one of the latest technologies available, yet despite considerable research and progress in mapping the bovine genome, genomics is not a widely used tool in the cattle industry.

Current use of genomics

Currently genomics is used in the beef industry to determine parentage as well as to identify which animals carry qualitative and quantitative traits.

Parentage

Identifying the parentage of cattle is a critical factor in assessing estimated progeny differences (EPDs).

The report states that using genomics for parentage allows seedstock producers to manage multiple sire breeding pastures and settle artificial insemination (AI)/ natural sire discrepancies when birth dates are inconclusive.

Genomics parentage testing enables an increase in the amount of information used to estimate an animal’s genetic merit, thereby improving the accuracy of prediction of the estimate although not necessarily affecting the predicted value.

Qualitative traits

Qualitative traits are those such as coat colour, horned/ polled, which are controlled by a single pair of genes that have a simple recessive inheritance.

Genomics can be used to identify cattle that are carriers of recessive genes facilitating selection against the carriers, if desired; or make more informed mating decisions. The greatest value of these tests is to identify and manage lethal recessives; this technology has saved the beef industry countless dollars, says the report.

Quantitative traits

The third use is to select cattle for more commercial traits, which are controlled by multiple pairs of genes and influenced by the environment, such as birth weight, carcase fat etc.

There are a number of ways to combine genomic and phenotypic information into a single selection tool. Breeding values based on genomics information for a variety of traits are now available from multiple commercial companies and can be used as selection tools.

However, there is no evidence to suggest that these tools provide a better selection tool than EPDs and the likely best use of this information, says the report, is to combine it with phenotypic information in a genetic evaluation to compute genomically enhanced EPDs.

The American Angus Association was the first breed organisation to augment their EPD with genomic information, however several other breeds have shown interest in taking advantage of this technology since then.

Challenges

An early and ongoing challenge to adoption of genomics is getting producers to understand what genomics is about, however demonstrating financial benefits is also a challenge.

Outside of seedstock production, demonstrating an economic driver to the industry has proven difficult, despite the benefits of genomics being seen further up.

Today, the costs of genomics testing tend to exceed the value that is returned to any single sector.

The current marketing structure is for seedstock producers to collect DNA for pedigree verification, genetic defect testing and possibly genomic enhanced EPDs and should pass that cost on through higher bull prices. Obtaining further genomics information results in re-collection and extraction of genomics information at additional costs to the new owner.

The report suggests that a better economic model could be developed so that cattle would be genotyped once early in life and genotypes shared among production sectors to derive the maximum value from the DNA collection and extraction costs incurred.

A promising future?

Cattle health

Incorporating disease resistance into a breeding programme would have significant benefits for the industry. One use would be to eliminate bovine respiratory disease (BRD) - an important cause of disease-related economic losses.

The White Paper says that there is evidence that BRD susceptibility has a genetic component, with low heritability. A five year study is underway to try and understand the genetic potential of animals to remain healthy and free of BRD, which will help identify and select cattle that are less susceptible to the disease.

Production

EPDs are a reliable tool to assist producers when selecting for production traits. However, genomics offers opportunities to improve the accuracy in these traits. On a within breed basis the development of genomic enhanced EPDs has been successful, says the report.

Having the data of genotyped animals available for a genomic test is not a possibility for all breeds and so the report suggests a robust across-breed set of genomic prediction equations.

Another benefit to the industry would be to focus more on input traits, such as feed intake and efficiency, especially when considering feed costs are between 60-65 per cent of production costs.

Reproduction

Given the economic importance of reproduction, it is crucial for commercial cow-calf producers to optimise reproductive performance in their herds.

Because of the low heritability of most reproductive traits and limited access to reproduction EPDs (heifer pregnancy rate and stayability in a limited number of breeds), the commercial beef sector has attempted to maintain high reproduction rates through crossbreeding and improved management practices with very little emphasis on selection.

The report states that genomic testing offers an attractive approach to provide these previously-absent selection criteria.

Beef consumption and health

The health impact of beef consumption is a topic of great debate. Studies have shown that altering the mineral and/ or fatty acid composition of beef does not have an effect on palatability.

Other studies have shown that genetic factors influence fatty acid composition. This report suggests that if genetic markers that impact fatty acid and mineral composition can be identified then selection for improved beef healthfulness can be achieved.

The full report can be found here.

Charlotte Johnston

TheCattleSite News Desk