Genetic improvement of feed conversion ratio via indirect selection against lipid deposition in farmed rainbow trout (Oncorhynchus mykiss Walbaum).
In farmed fish, selective breeding for feed conversion ratio (FCR) may be possible via indirectly selecting for easily-measured indicator traits correlated with FCR. We tested the hypothesis that rainbow trout with low lipid% have genetically better FCR, and that lipid% may be genetically related to retention efficiency of macronutrients, making lipid% a useful indicator trait. A quantitative genetic analysis was used to quantify the benefit of replacing feed intake in a selection index with one of three lipid traits: body lipid%, muscle lipid% or viscera% weight of total body weight (reflecting visceral lipid). The index theory calculations showed that simultaneous selection for weight gain and against feed intake (direct selection to improve FCR) increased the expected genetic response in FCR by 1·50-fold compared with the sole selection for growth. Replacing feed intake in the selection index with body lipid%, muscle lipid% or viscera% increased genetic response in FCR by 1·29-, 1·49- and 1·02-fold, respectively, compared with the sole selection for growth. Consequently, indirect selection for weight gain and against muscle lipid% was almost as effective as direct selection for FCR. Fish with genetically low body and muscle lipid% were more efficient in turning ingested protein into protein weight gain. Both physiological and genetic mechanisms promote the hypothesis that low-lipid% fish are more efficient. These results highlight that in breeding programmes of rainbow trout, control of lipid deposition improves not only FCR but also protein-retention efficiency. This improves resource efficiency of aquaculture and reduces nutrient load to the environment.
1Biometrical Genetics, Natural Resources Institute Finland,FI-31600 Jokioinen,Finland.
Antti
A
Kause
2Department of Animal Nutrition and Husbandry, Swedish University of Agricultural Sciences,750 07 Uppsala,Sweden.
Anders
A
Kiessling
3School of Biological Sciences,University of Aberdeen,AberdeenAB24 2TZ,UK.
Samuel A M
SA
Martin
3School of Biological Sciences,University of Aberdeen,AberdeenAB24 2TZ,UK.
Dominic
D
Houlihan
4EWOS Innovation AS,N-4335 Dirdal,Norway.
Kari
K
Ruohonen
D050154:Adiposity; D000818:Animals; D017756:Aquaculture; D018752:Diet, Fat-Restricted / Q000662:veterinary; D004041:Dietary Fats / Q000032:analysis; D002149:Energy Intake; D005260:Female; D005387:Finland; D050152:Intra-Abdominal Fat / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism; D050356:Lipid Metabolism; D008297:Male; D008954:Models, Biological; D054647:Nutrigenomics / Q000379:methods; D017686:Oncorhynchus mykiss / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D011897:Random Allocation; D017747:Seafood / Q000032:analysis; D012641:Selection, Genetic; D000068618:Selective Breeding; D015430:Weight Gain
D004041:Dietary Fats
 
                  VG genetic variance;  
                  VR residual variance;  
                  b
                Regression coefficient;  
                  h
                  2
                heritability;  
                  r
                  G
                genetic correlation;  BW body weight;  DFI daily feed intake;  DG daily weight gain;  FCR feed conversion ratio;  HP high protein;  NP normal protein;  RFI residual feed intake; Breeding programmes; Feed intake; Index selection; Quantitative genetics