Saturday, May 13, 2017

EBVs: The Next Step

For the past 11 years, the Western Maryland Pasture-Based Meat Goat Performance Test has evaluated meat goat bucklings, mostly Kiko and Kiko crosses, for growth (on pasture), parasite resistance (fecal egg counts), parasite resilience, and various other traits. Buck tests are a good start to genetic improvement, but it is time for the meat goat industry to move onto EBVs.

EBV stands for estimated breeding value. An EBV is an estimate of an animal’s genetic merit for a specific trait. EBVs can be calculated for any trait that can be measured, including number of kids born, number of kids weaned, weaning weight, post-weaning weight, loin depth, and parasite resistance.  Indexes are often created to aid in selection decisions. They can be tailored to specific breeds or goals. For those familiar with EPDs (for cattle), an EPD is half the numeric value of an EBV.

EBVs can measure maternal traits: buck tests cannot.

EBVs are far more accurate than the (raw) data collected in a buck test because they factor in data from an animal’s relatives (sire, dam, siblings, even distant cousins), as well as other traits. In the calculation of EBVs, genetic correlations and heritabilities are also considered. Because the performance of crossbred animals is influenced by hybrid vigor (heterosis),  EBVs can only be calculated for purebreds or animals containing a high percentage of a single breed. This may eventually change. It is in cattle. To be truthful, it was not fair to compare the performance of purebred bucks in the Maryland test with crossbred bucks.

Other countries and animal industries have been using EBVs for many years, with well-documented successes.The National Sheep Improvement Program (NSIP) calculates EBVs for sheep and meat goat producers in the US. Data is processed by Sheep Genetics of Australia, which has both a LambPlan and KidPlan.