Reducing the Common Environmental Effect on Litopenaeus vannamei Body Weight by Rearing Communally at Early Developmental Stages and Using a Reconstructed Pedigree

摘要

Heritability estimates may be severely biased when a large common environmental effect on a family arises from a longlasting separate rearing at early stages(SRES)in traditional selective breeding programs,especially when bred populations have weak genetic ties.Communal rearing at early stages(CRES)may reduce common environmental effect since all families are reared in the same environment immediately after hatching.Here,we compared the effects of CRES and SRES strategies on genetic parameter estimation for harvest body weight in a selective breeding population of Litopenaeus vannamei with a small number of half-sib families.Genetic parameters of each strategy were estimated by using animal models excluding and including the common environmental effect(Model 1 and Model 2,respectively).Heritability estimates for body weight were 0.21±0.06(P0.05)in Model 2.The ratio of common environmental variance to phenotypic variance was 0.002±0.000 and 0.071±0.112 for CRES and SRES,respectively.Neither strategy precisely partitioned the common environmental variance according to likelihood ratio test.Lower heritability for body weight in CRES than in SRES implied that a large common environmental variance was confounded with additive genetic variance and was not effectively partitioned in SRES.Moreover,genetic correlation of body weight between the two strategies was 0.75±0.15,indicating that family rankings truly changed.The CRES should be followed in the selective breeding program of shrimp,especially in a population with a shallow pedigree and weak genetic ties between families.