By Troy Rowan
When we look back at the evolution of genetic improvement in the beef industry most all of our major improvements have come relatively recently. Each of the steps in this evolution improved the accuracy with which we make selection decisions. This increase in selection accuracy led to jumps in rates of genetic improvement. From the visual appraisal that drove selection decisions to the current genomic-enhanced EPD calculations, individual animal phenotypes have been absolutely essential. As the industry looks to the next frontier of genetic improvement, our ability to capture important phenotypes will be as critical as ever. The development of new technologies are making the capture of phenotype easier, more precise, and widely applicable across the beef industry.
Historical developments in genetic improvement programs
The history of selectively breeding beef cattle looked largely the same from the dawn of domestication until the 1950s. Only then did widespread performance testing programs begin that allowed us to more precisely measure differences between animals at a level beyond visual appraisal. These programs aimed to standardize measurements and use contemporary groupings to identify genetic outliers within common management groups. The next major leap in improving selection accuracy came with the advent of expected progeny difference (EPD) calculations from this performance data. The EPD calculations leveraged both the phenotypes collected by performance programs and information from the deep pedigrees kept by breed associations to make more accurate estimates of animal genetic potentials. The subsequent five decades contained incremental and large improvements to EPD accuracy, including the addition of genomic information.
While we continue to make incremental improvements in how we calculate EPDs, I would argue that the next great leaps in beef genetics will come from measuring new phenotypes for things that drive profitability across the industry.
Phenotypes: The currency of genetic evaluations
EPD calculations rely on the widespread collection of phenotypes that capture the traits driving profitability to breeding programs. This can range from calving ease scores to weaning weights to fertility outcomes to carcass quality. EPDs can be calculated on any phenotype that can be measured on a very large number of animals. More records result in a more accurate EPD, but there is often an inverse relationship between the number of phenotypes collected and the difficulty of measurement. It’s worth noting that data quality matters just as much as data quantity. Inconsistent scoring or measurement error across operations can erode EPD accuracy just as quickly as a shortage of records. Often, we rely on “indicator phenotypes” to ramp up the number of records captured. For example, capturing real carcass records on registered animals is quite difficult, motivating the use of live animal carcass ultrasound as a useful indicator trait for building greater numbers of phenotypic records. It is also important to remember that phenotype collection must remain consistent, even after the number of records is sufficient to calculate an accurate EPD. The models that produce EPDs need to be constantly trained on new phenotypes to maintain their accuracy.
Source : tennessee.edu