Selection responses in survival of Macrobrachium rosenbergii after performing five generations of multi-trait selection for growth and survival

A selective breeding program was established to improve the growth and survival of the cultured giant freshwater prawn Macrobrachium rosenbergii. The response to selection was estimated for the survival of M. rosenbergii using a fully pedigreed synthetic population formed by three introduced strains. The data included 122,761 progeny from 437 sires and 723 dams in seven generations with a nested mating structure. The genetic parameters and estimated breeding values (EBVs) were estimated using a generalized linear mixed model with the probit link function. The realized response was estimated from the difference in the marginal means of survival for the selection and control populations, while the predicted response was obtained from the difference in the mean retransformed survival rate based on the survival EBVs between generations. The realized genetic gain in survival from the G(1) to G(6) generation ranged from -1.24 to 2.72 %. The accumulated realized genetic gain (5.02 %) expressed as a percentage was 8.46 %. Across the generations, high heritability (0.401 +/- A 0.020, Set 1) was obtained when using the model without the c effect and was significantly different from zero (P < 0.05). However, the low heritability and common environment (0.013 +/- A 0.011 and 0.088 +/- A 0.007, Set 2) were estimated using the model that included the c effect. The accumulated predicted gains (6.29 and 0.61 %, respectively) from the Set 1 and Set 2 parameters over the five generations of selection expressed as proportions were 9.08 and 0.87 %, respectively. The low genetic gain for survival is most likely caused by a low relative weight in the selection index and reduced genetic variation because of consecutive between-family selection.