“When we look at genetic improvement, we want to focus on traits that contribute to the economic performance of the animals,” said project lead Dr. John Crowley, Director of Scientific and Industry Advancement with the Canadian Beef Breeds Council (CBBC) and a research geneticist with Livestock Gentec at the University of Alberta.
Playing the weighting game
Since honing in on one trait at a time slows down genetic improvement, the preference is to examine several traits at once. Of course, Dr. Crowley and his team recognize that a lot of characteristics fall under the heading of “economically important”, including weaning weights, fertility, feed efficiency, carcass weight, marbling and many others.
To ensure they choose the options that would most benefit the industry, researchers assign each trait a different weight of importance based on their analysis of a total production system.
“We develop the indexes by analyzing a beef production system and identifying which traits have the greatest economic impact or weight,” said Crowley.
Watching their weights
Those economic weights are calculated using a bio-economic model, which is a mixture of the economics of a production system and the genetic architecture (variance) of traits in the population you’re selecting.
“In the modern age of animal breeding, genomics plays a big part in influencing that model by increasing selection accuracy and reducing the generation interval. And, everything else being equal, the shorter the generation interval, the faster the rate of genetic progress per annum resulting from selection.”
In building their model, researchers scrutinize the inputs and outputs of a production system and model male and female lives from beginning to end: how they interact, current feed and slaughter prices and costs associated with various levels of calving difficulty, among many other variables.
“At the end of the day, we examine the costs of producing the animals and the revenues derived from selling them and ask ‘where will the biggest improvements in production efficiency come from? Which traits will make the biggest difference?’”
Worth the weight
Some choices may seem clear at first glance; for example, female fertility captures the greatest relative emphasis in selection indexes around the world. But as Crowley pointed out, there is generally an inverse relationship between fertility and production, so improving them both at the same time is difficult.
Also, a breeder may have a dozen breeding values – measures of genetic merit for a specific trait – for each bull.
“When you’re comparing 50 bulls to each other, some will be at the top for some traits and at the bottom for others. With so many factors impacting the profitability of bulls, it’s hard to pick out one animal based on all of those traits.”
Using selection indexes, however, a lot of information can be refined into one or two index numbers which can then be given to the producer to simplify his choices.
While a lot of work remains to be done, researchers hope that by combining genomics with economic weights and selection indexes, they can make the cattle farmer’s job easier and more productive. Okay, maybe they won’t shed any light on the true nature of navel fluff, but hey, you can’t have everything.