Research

Background

Hybrid vigour, also known as heterosis, is a phenomenon that occurs when two genetically distinct animals are crossed. This often results in a boost in both moderately and lowly heritable traits, such as growth, fertility, disease resilience, longevity, etc.  The largest hybrid vigour effect occurs in the offspring of two purebred animals of different breeds (100%). This is called the F1 generation. If that F1 calf is crossed to a purebred animal of yet another breed, the hybrid vigour of the resulting F2 calf would remain at 100%; but, if that F1 calf is crossed back to one of its parent’s breeds, hybrid vigour drops to 50%. If the same bull breed on a commercial operation continues to be used year after year, and replacements are home grown, the hybrid vigour level will continue to drop in future generations. There’s an economic benefit too – some research has indicated that cows with higher hybrid vigour averaged $161 greater net annual returns.

If you know the exact breed composition of your herd, predicting heterosis just takes a little math. But it isn’t always possible to know the exact percentage of those Simmental x Angus cows you bought at Joe’s dispersal two years ago. Igenity® Envigor™ can predict breed composition just like if you knew the exact pedigree back generations. But there’s a bit more to the story than that. The Envigor™ test can tell you that your animal is 75% and 25% Simmental and give you a hybrid vigour score based on that information. Due to the different ways genes combine in different breeds and breed specific single nucleotide polymorphisms (SNPs) at the molecular level, a 75/25% Angus x Simmental cross could have different potential for hybrid vigour than a 75%/25% Simmental x Angus, even thought you would arrive at the same hybrid vigour percentage for both crosses by pedigree. This project will attempt to quantify the molecular contribution to hybrid vigour.

Confused? Check out the BCRC’s Genomics & Genetic Testing Topic Page, Record Keeping Modules and Email Course

Objectives

The objectives of this project are to:

1. Use existing purebred and crossbred data sets for growth, feed efficiency, carcass merit and female fertility to conduct genome wide association studies to identify DNA variants associated with hybrid vigour
2. Develop indicators of hybrid vigour at the DNA level
3. Quantify relationship of the indicators to observed trait performance
4. Validate indicators in independent datasets of purebred and crossbred cattle

Implications of the Research

If successful, this project will substantially advance our knowledge of how hybrid vigour occurs, how to effectively optimize it for different operations, and improve the currently available test.