The genetic analysis of tolerance to infections : a review

v2012o

Kalojen rehunkulutus paljastuu röntgenissä

Viljeltyjen kalojen yksilöllinen rehunkulutus voidaan mitata syöttämällä niille rehua, jossa on röntgenkuvassa näkyviä pieniä lasikuulia. Menetelmällä pystytään mittaamaan tuhansien kirjolohiyksilöiden rehunkulutus. Toisaalta rehunkulutus vaihteli päivästä toiseen ennakoitua enemmän. Siksi yksilöiden rehunkulutuksen mittaamisessa tarvitaan useita toistomittauksia ja kalat tulisi myös mitata kasvun eri vaiheissa. Menetelmällä on tutkittu kirjolohen ja siian eläinjalostusohjelmissa rehutehon jalostettavuutta.vo

Kasvatetun siian ominaisuuksien taloudelliset arvot

vokBEL/BG

Changes in the expression of genetic characteristics across cohorts in skeletal deformations of farmed salmonids

Genetic analysis of disorder incidence in farmed animals is challenged by two factors. Disorders in different cohorts and environments could be caused by different factors, leading to changes in heritability and to less than unity genetic correlations across cohorts. Moreover, due to computational limitations, liability scale heritabilities at very low incidence may differ from those estimated at higher incidence. We tested whether these two dilemmas occur in skeletal deformations of farmed salmonids using multigeneration data from the Finnish rainbow trout breeding programme and previous salmonid studies. The results showed that heritability was close to zero in cohorts in which management practices maintained incidence at a low level. When there was a management failure and incidence was unusually high, heritability was elevated. This may be due to computational limitations at very low incidence and/or because deformations are induced by different factors in different cohorts. Most genetic correlations between deformations recorded in different generations were weakly to strongly positive. However, also negative correlations between generations were present, showing that high liability at one time can be genetically connected to low liability at another time. The results emphasise that genetic architecture of binary traits can be influenced by trait expression

Selection potential for feed efficiency in farmed salmonids

vokBEL/BG

Breeding salmonids for feed efficiency in current fishmeal and future plant-based diet environments

The aquaculture industry is increasingly replacing fishmeal in feeds for carnivorous fish with soybean meal (SBM). This diet change presents a potential for genotype-environment (G × E) interactions. We tested whether current salmonid breeding programmes that evaluate and select within fishmeal diets also improve growth and efficiency on potential future SBM diets. A total of 1680 European whitefish from 70 families were reared with either fishmeal- or SBM-based diets in a split-family design. Individual daily gain (DG), daily feed intake (DFI) and feed efficiency (FE) were recorded. Traits displayed only weak G × E interactions as variances and heritabilities did not differ substantially between the diets, and cross-diet genetic correlations were near unity. In both diets, DFI exhibited moderate heritability and had very high genetic correlation with DG whereas FE had low heritability. Predicted genetic responses demonstrated that selection to increase DG and FE on the fishmeal diet lead to favourable responses on the SBM diet. Selection for FE based on an index including DG and DFI achieved at least double FE gain versus selection on DG alone. Therefore, current breeding programmes are improving the biological ability of salmonids to use novel plant-based diets, and aiding the aquaculture industry to reduce fishmeal use

Genetically determined resistance and tolerance to Diplostomum sp. parasite in farmed rainbow trout

Parasite infectivity, virulence and host resistance have been in the centre of the scientific interest when it comes to host-parasite relationships. In addition to resistance, hosts may also vary in their tolerance against parasites. This is important to notice because resistance and tolerance have different consequences in host-parasite co-evolution. Here, we show that families of farmed rainbow trout (Oncorhynchus mykiss) show both host defence strategies, resistance, and tolerance, against infectivity and virulence ofDiplostomumsp. (Trematoda) parasites. Both strategies have moderate genetic variation and are genetically independent of each other. It is also shown that the families having the highest performance measured as higher weight, better condition factor and lower mortality in absence of the parasites suffer the most when parasitism increases. For practical breeding programmes, this means that both resistance and tolerance can be improved by selection without compromising one of the strategies. These results give new insight into defence strategies against parasites in fish and into processes of fish-parasite co-evolution.Peer reviewe

Untangling the positive genetic correlation between rainbow trout growth and survival

Peer reviewe

Restored river habitat provides a natural spawning area for a critically endangered landlocked Atlantic salmon population

Supplementing endangered fish populations with captive bred individuals is a common practice in conservation management. The aim of supplementary releases from hatchery broodstocks is to maintain the viability of populations by maintaining their genetic diversity. Landlocked Lake Saimaa salmon (Salmo salar m. sebago) has been critically endangered for the past half-century. As a result of anthropogenic disturbance, especially construction of hydroelectric power plants, the Lake Saimaa salmon has become completely dependent on hatchery broodstock. Recently, habitat restoration has been done in one of the former spawning rivers with the aim of creating a new natural spawning ground for the critically endangered population. Hatchery fish releases have also been revised so that in addition to juveniles, adult fish from the hatchery and from the wild have been released into the restored river. We assessed here if a restored river stretch can be used as a natural spawning ground and juvenile production area with the aim of improving genetic diversity of the critically endangered Lake Saimaa salmon. By constructing a pedigree of the released adults, and juveniles sampled from the restored river, we found that the majority of the released adults had produced offspring in the river. We also found that wild-caught spawners that were released into the restored river had much higher reproductive success than hatchery-reared parents that were released into the restored river at the same time. We found no significant differences in genetic diversity between the parent and offspring generations. Meanwhile, relatedness among different groups of adults and juveniles varied a lot. For example, while the hatchery-reared females were on average half-siblings, wild-caught females showed no significant relatedness. This highlights the importance of using pedigree information in planning the conservation and management of endangered populations, especially when artificial propagation is involved.Peer reviewe