A comparison of communal and separate rearing of families in selective breeding of common carp (Cyprinus carpio): Responses to selection

The genetic response in growth traits in a selection program for increased harvest weight in a common carp population in Vietnam is reported. A base population (G0) was established from six carp stocks using single pair mating. Selection was based on high breeding values for body weight at harvest, with a corresponding control group selected on average breeding values of the population. In the following two selected generations (G1 and G2), families were produced using a partial factorial mating design. Each family in G1 and G2 was split and reared using communal early rearing (CER) or separate early rearing (SER) methods. Molecular markers were used to maintain pedigree information in CER whereas physical tagging was applied in SER. Both CER and SER were managed under otherwise similar conditions. The data for growth traits were analyzed using a univariate mixed model to estimate breeding values, variance components and response to selection. Response to selection was estimated by two different methods: (i) comparing the least squares means of the selection and control lines, and (ii) comparing the estimated breeding values of the selection and control lines. In CER, the response to selection for body weight and length varied from 15.0% to 21.4% and 4.0% to 7.2% per generation, respectively, at final measurement. In SER, the responses to selection were lower for both traits, varying from 7.9% to 8.2% and 3.5% to 4.1% per generation for weight and length, respectively. The estimated responses to selection based on least squares means were in good agreement with those calculated from breeding values. Selection under the CER rearing system resulted in greater estimated genetic response relative to SER. The reasons why this may have happened are discussed