Genome Scientists Play “Rate the Trait” by: Geoff Geddes

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Everything in life is a trade off: Marry the woman of your dreams; then brace for the in-laws. Fortunately, genomics has the potential to change the rules when it comes to beef cattle, enabling producers to enjoy the upside of key traits without enduring the downside. Tapping that potential is the focus of the Genome Alberta project targeting traits of interest to the beef industry such as feed efficiency, productivity and methane emissions.

“The profitability of beef cattle production is determined by multiple traits that are sometimes negatively correlated,” said Dr. Changxi Li. Dr. Li is a research scientist with Agriculture and Agri-Food Canada (AAFC) and AAFC Professor and Chair of Bovine Genetics, Faculty of Agricultural, Life and Environmental Sciences at the University of Alberta. “That means if you select for one desirable trait, such as growth, it may have a negative impact in another area by increasing the animal’s feed requirements.”

To counter that effect, researchers are building up an index that considers multiple traits at one time and determines the economic weight of each trait based on costs and revenues. As an example, for every 1 kilogram that you increase body weight, how much extra will that add to production costs and net revenues?

“Once we calculate the exact economic weight and value of these traits, we can use that information to construct a multiple trait selection index for each animal,” said Dr. Li. “From there, we will define the most important traits to include in the index based on their economic weight and genetic components like genetic and phenotypic variances, heritability and molecular breeding value.”

Staying true to their values

Through all of these calculations, the molecular breeding value is a key component for each animal and each trait in addition to the economic weight. Where scientists lack phenotype information on an animal, those values can be predicted based on the animal’s DNA profile (i.e. genomic prediction), and be used to produce the index that weighs one trait against all the others. In this way, they will know from day one if a cow will be profitable, and be able to identify the best animals when it comes to lifetime productivity.

“For the replacement heifer index, we are considering several different traits, for which we have data from 411 animals over 11 production cycles,” said Dr. Tiago Valente, a post-doctoral researcher in Animal Breeding and Genetics at Livestock Gentec, University of Alberta.

Those traits include heifer birth weight, weaning weight, retained heterozygosity or hybrid vigor (the improved function of any biological quality in a hybrid offspring), dry matter intake, residual feed intake or feed efficiency, cow productivity, age at first calving and number of progenies from 1 – 5.

“We chose these traits for the index because we view them as having the greatest impact on revenue,” said Dr. Valente.

In selecting them, researchers are looking for three aspects in regard to replacement heifers: new traits with additional costs, such as feed efficiency; readily accessible traits that are easy to measure, like age of first calving; and late phenotypes such as the number of progeny.

“Our hope is that we can use this selection index to help producers choose the best cows that produce the most revenue and the least methane, thereby supporting sustainability,” said Dr. Valente.

While these are exciting times for both scientists and beef producers, Dr. Li has a couple of key reminders.

“It is important to emphasize that genetics provides potential and management helps deliver that potential. As genomics research evolves, new tools like genomic prediction of genetic potential or of retained hybrid vigor can aid producers in selecting the optimal genetics or breed combination for their herd. This will help them make breeding and selection decisions for improving cattle performance, including traits that are more difficult and expensive to measure such as feed efficiency, fertility and methane emission.” 

Dr. Li also stresses that genetic improvement in a herd is cumulative and sometimes progress is slow, so the best approach is to continuously select for the traits you desire over many breeding seasons.

Now if you could only choose your in-laws…

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