Genetic heterogeneity of residual variance in GIFT Nile tilapia

J. Marjanovic, H.A. Mulder, H.L. Khaw, P. Bijma

Research output: Chapter in Book/Report/Conference proceedingAbstract


In animal breeding, ample success has been achieved in improving mean levels of trait values by means of genetic selection. However, the same has not been realized for variability of trait values among individuals. Selection for more uniform individuals is possible only in the presence of genetic variation in trait variability. This phenomenon is known as genetic heterogeneity of environmental (residual) variance. The aim of this study was to investigate the potential for genetic improvement in variability of harvest weigh (HW) in the GIFT strain of Nile tilapia, by applying double hierarchical generalized linear models. This approach offers simultaneous estimation of genetic parameters for the mean and the residual variance, which is modelled on the exponential scale. Both untransformed and Box-Cox transformed HW were analysed to study the impact of non-normality on estimates of variance components. Analysis involved 6,090 fish with records on HW. We found substantial genetic variation in the residual variance of 0.41, which decreased to 0.27 after the transformation. The given estimates are on a log scale. The genetic coefficients of variation for residual variance were 64% and 52% on untransformed and transformed scale respectfully. These values describe the potential decrease in residual variance when achieving one genetic standard deviation by selection. The genetic correlation between mean and variance was 0.67 for untransformed HW, which points to a strong relationship between both traits. The genetic correlation for Box-Cox transformed HW was 0.12. The results obtained in this study indicate a good opportunity to improve variability of HW. The high genetic correlation of 0.67 between HW and residual variance suggests necessity for index selection in order to increase HW and reduce its variation at the same time.
Original languageEnglish
Title of host publicationBook of Abstracts of the 66th Annual Meeting of the European Federation of Animal Science
Place of PublicationWageningen
PublisherWageningen Academic Publishers
ISBN (Print)9789086862696
Publication statusPublished - 2015
EventEAAP - 66th Annual Meeting 2015 - Warsaw, Poland
Duration: 31 Aug 20154 Sept 2015


ConferenceEAAP - 66th Annual Meeting 2015


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