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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2007-0332v1 85/12/3218    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kause, A. Articles by Koskinen, H. Search for Related Content PubMed PubMed Citation Articles by Kause, A. Articles by Koskinen, H.

Direct and indirect selection of visceral lipid weight, fillet weight, and fillet percentage in a rainbow trout breeding program¹

A. Kause^*,2, T. Paananen, O. Ritola and H. Koskinen

^* MTT Agrifood Research Finland, Biotechnology and Food Research, Biometrical Genetics, FI-31600 Jokioinen, Finland; and and Finnish Game and Fisheries Research Institute, Tervo Fisheries Research and Aquaculture, FI-72210 Tervo, Finland

² Corresponding author: Antti.Kause{at}mtt.fi

We assessed whether visceral lipid weight, fillet weight, and percentage fillet from BW, 3 traits laborious to record, could be genetically improved by indirect selection on more easily measured traits in farmed rainbow trout. Visceral lipid is discarded as waste during slaughter, influencing production efficiency and production costs. Fillet weight and fillet percentage directly influence economic returns in trout production. The study comprised 3 steps. First, we assessed the degree to which selection on percentage of visceral weight from BW indirectly changes visceral lipid weight and the size of intestines and internal organs. The phenotypic analysis of weights of viscera, intestines, visceral lipid, liver, and gonads measured from 40 fish revealed that phenotypic selection against visceral weight was most strongly directed to visceral lipid, and to a lesser degree to intestines and gonads. Because genetic relationships among these traits were not established, it is not known whether indirect selection leads to genetic responses. Second, we examined whether direct selection for the fillet traits could be replaced by indirect selection on BW, eviscerated BW, visceral weight, visceral percentage, head volume, and relative head volume (head volume relative to BW). The selection index calculations based on the quantitative genetic parameters obtained from multigenerational pedigree data showed that genetic improvement of fillet percentage through direct selection (selection accuracy, r_TI = 0.54) was equally efficient compared with indirect selection on visceral percentage ( r_TI = 0.54). Genetic improvement of fillet weight through direct selection (r_TI = 0.56) was always more efficient than indirect selection, yet indirect selection for eviscerated BW ( r_TI = 0.50) was almost as efficient as direct selection. Third, the expected genetic responses to alternative selection indices showed that improved fillet percentage was mainly a result of a moderate decrease in visceral weight rather than of a major increase in absolute fillet weight. Moreover, fillet percentage is challenging to improve, even if it exhibits moderate heritability (h² = 0.29). This is because fillet percentage displays low phenotypic variation. In conclusion, fillet weight and fillet percentage can be increased by indirect selection against visceral percentage and for high eviscerated BW.

Key Words: fillet yield • genetic correlation • heritability • lipid deposition • quantitative genetics • rainbow trout