Comparison between optimum contribution and mate selection in coho salmon breeding

The objective of this study was to compare optimum contribution selection (OCS) and mate selection (MS) in a coho salmon (Oncorhynchus kisutch) breeding program, regarding parameters associated to genetic progress and inbreeding. The dataset contained pedigree information and standardized economic index of 79,144 coho salmon from eight generations. The top three males and four females with positive economic index from 112 families of the eight generation were considered as selection and mate candidates. The target objective function (OF) to be optimized was: OF = w1*x'EBV + w2*x'Ax + w3*, where w1, w2 and w3 are the weights associated to the expected genetic merit of the future progeny (x'EBV), the coancestry of selected parents (x'Ax) and the predicted average inbreeding of the future progeny (), respectively, and x is the vector of genetic contributions for each candidate, to be optimized. A differential evolutionary algorithm was used in the optimization process. Different OF were tested (OF1 to OF9), varying the weights for each component. The OF1 corresponded to BLUP selection, as w2 and w3 were assumed equal to zero. Its results were used as a reference for comparison with those from the other OF. In OF2 and OF3, x'Ax andwere maximized, respectively, to explore their parametric space, setting the weights for the other components to zero. The x'Ax increased by 12.37% in OF2, and increased by 10.37% in OF3, compared to OF1. OF4 to OF6 assumed w3=0 and corresponded to OCS under different weights for coancestry. Compared to OF1, OCS resulted in a reduction of x'Ax from 0.68 (OF4) to 5.68% (OF6), and a reduction of x'EBV from 0.02 (OF4) to 3.65% (OF6). In the application of OCS followed by minimum inbreeding (OF7) and mate selection (OF8 and OF9) the reduction in was equal to 0.88, 10.21 and 11.03% for OF7, OF8 and OF9, respectively, compared to OF1. The MS outperformed OCS and OCS followed by minimum inbreeding in controlling inbreeding, under similar levels of genetic merit and coancestry, indicating advantage of performing selection and mating decisions simultaneously.