For the commercial cattle producer, crossbreeding is one of the least expensive ways to increase productivity, largely due to the resulting increase in hybrid vigour (scientifically known as heterosis / heterozygosity). In spite of this knowledge, the past 30 years have seen a continual erosion in heterosis in the cow herd as colour and “uniformity” became one of main considerations of cattle buyers. Crossbreeding, in contrast combines superior genetics from different breeds while eliminating any inbreeding depression. The Beef Cattle Research Council article “Have You Rotated Your Breeds Lately?” provides an excellent overview of why inbreeding depression occurs and some ways in which crossbreeding pays off so well for producers.
New tools are being developed that allow producers to use DNA to quantify heterosis (via breed composition) with an accuracy of 96%. This is superior to the degree of accuracy achieved with even the most accurate pedigree records due to the phenomenon of genetic “re-shuffling” that occurs on each chromosome in every generation. For example, an accurate pedigree calculation for a 100% Simmental bull crossed with a 50% Angus / 50% Hereford cow records a calf that is 50% Simmental x 25% Angus x 25% Hereford. In fact, the true genetics of the animal as a result of this “re-shuffling” might be 50% Simmental x 15% Angus x 35% Hereford. As an aside, the genomics method of breed composition automatically captures the neighbour’s bull who thinks the “grass” is greener on the other side of the fence.
But back to hybrid vigour… It is important to calculate heterosis accurately because the benefits are proportional (the greater the heterosis, the greater the benefits), the most economically important of which impact fitness, longevity, and reproductive productivity, the magnitude of which are as follows:
Every 10% increase in Vigour increases:
Pregnancy Rate +2% 2 more pregnancies per 100 cows*
Weaning Rate +3% 3 more weaned calves per 100 cows
Lifetime Productivity +79lbs 79 additional pounds of saleable
calf over 5 calvings
Days in the Herd +51 days
So what does this mean for the commercial producer? Two things. One: knowing the heterosis present in heifers being considered as replacements helps you select for those animals that have the greatest probability of staying in the herd the longest and producing the most pounds of beef. At an estimated cost of $2,000 to develop a replacement heifer, the longer they last, the better your bottom line!
Second: knowing the genomics breed composition of your herd allows for the selection of those bulls / breeds that will allow you to continue to optimize your mating, selection, and culling decisions, the benefit of which have been estimated at over $200 as the return on the investment of a $45 genomic test. It’s all money in the bank.
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* As an example, an increase in average Vigour in a 100-cow herd from 50% to 70% would be expected to result in an additional 4 pregnancies and 6 weaned calves per year; 158 additional pounds of saleable calf / cow over 5 calvings; and an increase in the average number of days a cow stays in the herd of 101 days.