Simplified method for genetic slaughter yields improvement in common carp under European pond conditions

Demand for edible part yields, usually offered as headless carcass or fillets, is continuously increasing in all fish species. Therefore, slaughter yields are interesting traits for genetic improvement. However, phenotyping of slaughter yields cannot be done on live breeding candidates and the suitable alternative seems to be utilization of simple yield predictors in indirect selection recorded by ultrasound tomography. In this study, we evaluated the possibility of using ratio of abdominal fillet thickness (E8) either to the abdominal depth (E23) or as alternative to E23 – 2D_d abdominal depth (length between lateral line and abdominal part vertical to the dorsal fin) as predictors for genetic improvement of slaughter yields in common carp. The predictors were recorded on each fish at age of two years (E8/E23_2, E8/2D_d_2) and three years (market size) (E8/E23_3, E8/2D_d_3). An experimental stock was established from a partial factorial mating design of 27 dams and 29 sires. Phenotyping of simple yield predictors, headless carcass and fillet with skin yields (only market size), and other performance traits was done on 987 (second year) and 773 (market size) individuals, uniquely assigned to their parental pair. The predictors recorded on market sized fish showed slightly better heritability (0.41, 0.44), genetic correlations to the slaughter yields (0.78–0.86) and expected genetic gains (1.29–1.54%) of the slaughter yields. However, predictors recorded on two-year old fish showed a solid genetic potential for slaughter yields improvement (h2 = 0.27–0.40; rg = 0.64–0.72, expected genetic gain = 0.93–1.35%). These data suggest that the indirect selection for improved slaughter yields could be performed using simple and quickly-to-measure yield predictors, also applicable in two-year old fish that are much easier for handling and manipulation. These newest results could significantly simplify carp breeding program focused on genetic improvement of slaughter yields. •Carp slaughter yields can be improved without slaughtering the fish.•Ratio of two ultrasound measurements on live fish may be used for carp slaughter yields improvement.•Selection for slaughter yields can be effectively performed on carps a year before they reach market size.•Abdominal depth measured by ultrasound has its alternative in a dimension recorded by a measuring scale.