An Analysis Of Indirect Genetic Effect On Body Weight Of Fenneropenaeus Chinensis Under Restrict Feeding

With the rapid development of the aquaculture industry in recent years,the scale of culture has continued to expand,and many breeds have experienced germplasm degradation.Problems such as rising mortality,slow growth,and decline in disease resistance have hindered the further development of the aquaculture industry.Breeding of new varieties has become an important driving force for the development of the industry.In the traditional selective breeding work,the criterion for measuring the genetic improvement potential of an individual or a family is usually a breeding value,ie,an additive genetic effect value.Additive effect is the main genetic determinants of phenotypic value of a quantitative trait,but it is a direct genetic effect(DGE)for the trait itself,ignoring the genetic influence of social interaction among individuals in the same group.The expression of genes of an individual has an influence on the phenotypic values of others in the same group,which is indirect genetic effect(IGE).IGE is generated by social interaction among individuals in the group.Studies have shown that IGE accounts for a large proportion of total genetic variance.In the breeding process,the inclusion of IGE in genetic assessment can significantly improve social welfare traits such as growth and survival of poultry.IGE has been widely reported in animals and plants.For aquatic animals,the IGE genetic parameters of Nile tilapia,Atlantic salmon,and Penaeus vannamei have been reported.Chinese shrimp(Fenneropenaeus chinensis)is one of the most representative aquaculture species in China.The intraspecific competition among F.chinensis is a common phenomenon,such as compete for limited resources,attack each other,and cannibalism.Attacks among individuals under environmental stress and fight for food may affect the growth of shrimps.In this paper,we used the F.chinensis as the research object,using classical animal models and extended animal models with indirect genetic effects and the parental model of threshold traits to estimate the genetic parameters of harvest weight and survival traits in the breeding population.The research results provide a certain research basis for further improving the social welfare traits of the breeding population in F.chinensis.The results of this paper are as follows:1.An Analysis of Indirect Genetic Effect on Body Weight of Fenneropenaeus chinensis under Restrict FeedingIn order to study the indirect genetic effects of body weight in F.chinensis under restrictive feeding conditions,103 families of the eleventh generation of the breeding population were tested using a multi-family by multi-group design.They were reared for about three months with limited feed,and harvest body weight was measured for each individual.Genetic parameters of harvest body weight were estimated using an extended animal model including IGE.The results showed that IGE of body weight was significant whose contribution to the total genetic variance reached up to 75.03%.There was a negative covariance(-0.0379±-2.1900)between DGE and IGE.Based on the model with IGE,the ratio of total genetic variance to phenotypic variance was0.524±0.212,less than the traditional estimate of heritability(0.616±0.074).In addition,there was a negative genetic correlation between the direct and indirect genetic effects(-0.495),implying that the existence of competitive effects may be detrimental to selective responses.This study demonstrated that there exists strong social interaction(competition among individuals)in population of F.chinensis under restrictive feeding conditions,which had a heritable effect on body weight.Considering that the indirect genetic effect under the competitive environment has a greater negative impact on the selection,it is inadvisable to conduct breeding programs under competitive environment.2.An Analysis of Indirect Genetic Effect on Body Weight of Fenneropenaeus chinensis under live bait restrictive feeding modeIn order to study the indirect genetic effects of body weight in F.chinensis under live bait restrictive feeding mode,100 families of the twelfth generation of the breeding population were tested using a multi-family by multi-group design.They were reared for about three months with limited feed,and harvest body weight was measured for each individual.Genetic parameters of harvest body weight were estimated using an extended animal model including IGE.The results showed that IGE of body weight was significant whose contribution to the total genetic variance reached up to 220.83%.There was a negative covariance(-4.8704)between DGE and IGE.Based on the model with IGE,the ratio of total genetic variance to phenotypic variance was 0.494±0.259,less than the traditional estimate of heritability(0.530±0.116).In addition,there was a negative genetic correlation between the direct and indirect genetic effects(-0.742±0.126),stronger than feeding by formulated feed,implying that the live baits lead to more intense competitive interactions.3.An Analysis of genetic correlation between competitive performance and survival traits of Fenneropenaeus chinensis under live bait restrictive feeding modeIn order to explore the correlation between competitive and survival traits of shrimp in China and how to use IGE for breed high-survival population.In this paper,using the data of the Grouped Rearing Mode(GRM),the genetic parameters such as the DGE,IGE of body weight,and survival trait DGE were estimated using the double-trait model.The genetic correlation between harvested body weight IGE and survival trait DGE was calculated,and the effect of competition on the survival rate of Fenneropenaeus chinensis population was analyzed.A high-cooperation and low-cooperation contrast mode(HLCM)was designed to verify the above conclusions.The results showed that the genetic correlation between harvested body weight IGE and survival trait DGE in the GRM test population was-0.8137;The competitive interactions caused by a density of 78 tails/m~3 and a fresh live bait feed amount of 50%of the normal feed dose did not significantly reduce the survival rate.On the contrary,highly competitive groups in this environment have advantages in survival traits.Therefore,IGE can be used as an index to indirectly select high-survival groups in a competitive environment.4.Genetic correlation analysis of Fenneropenaeus chinensis harvest weight between Grouped Rearing Mode and Communal Rearing ModeThis article analyzes the genetic correlation between harvested body weights in the Grouped Rearing Mode(GRM)and the Communal Rearing Mode(CRM).The results showed that the correlation coefficient of harvested weight DGE between GRM and CRM test models was 0.5915,which showed a moderate degree of genetic correlation;the correlation coefficient between harvested weight IGE and CRM test pattern harvest weight DGE was-0.3434 in the GRM test model,showing a Low negative correlation.Therefore,when formulating a selective breeding program,two test modes,GRM and CRM,can be set simultaneously.Assigning different weighting factors to the IGE obtained in the DGE and CRM modes obtained under the GRM mode,develop a comprehensive selection index,Select individuals who have a faster growth rate in GRM mode and have stronger collaboration ability in CRM mode,further increase the choice response to harvest weight.