Testing established methods of early prediction of genetic merit in abalone broodstock
There is a need in the abalone industry to improve production animals. However, abalone are relatively slow growing animals and take several years to reach harvest size. This means that during the establishment of foundation broodstock populations it may be several years before the relative genetic merit of each of the broodstock can be determined and the first selection decisions made. During this time, the hatchery manager will have to blindly spawn broodstock to stock the farm, often with broodstock possessing poor gEBV and that produce slow growing animals. This comes at the additional cost of not being able to cull poor performing broodstock early in the establishment of the population and replacing them with new broodstock.
Through measuring the family performance (and thus broodstock gEBV) of these cellular traits in larvae and comparing broodstock gEBV with those derived from progeny at harvest, a high genetic correlation would indicate that it is possible to predict genetic merit using these cellular traits. Studies have shown that the ratio between RNA and DNA in cells has a high heritability (necessary for the traits to have predictive power) and that it can be used to accurately predict the gEBV of barramundi broodstock without the necessity of rearing progeny all the way through to harvest (genetic correlation >0.8). Therefore, using RNA/DNA as the trait to measure in barramundi larvae it is now possible to establish high performing broodstock foundation populations via mass-spawning broodstock, estimating their genetic merit based on larvae RNA/DNA, and then eliminating those broodstock with inferior gEBV from the breeding population.
Several Australian barramundi hatcheries now apply this technique to assist in the selection of broodstock. This method is as yet untested in abalone, but if successful, has great potential in helping screen broodstock. This project will test the efficacy of this early prediction method in abalone. The impact of this early detection method would be to save costs by assisting in the selection of superior broodstock individuals which would produce faster growing offspring. Currently new broodstock animals are unevaluated with regard to their genetic merit.
Final report
The implications of this study are that grow out of progeny to harvest size (or close to) is currently still required to determine the genetic merit of abalone broodstock in selective breeding programs. Furthermore, future studies following the same individuals in a cohort through time are required to better understand the result that the genetic effect is only realised at the harvest stage. This work is required to better inform current grading practices. Furthermore, a moderate heritability for growth traits was detected and so there is also potential for farmers to improve growth of stock through selection.
