Nye indikatoregenskaper for individuell fôreffektivitet hos Atlantisk laks (Salmo salar)

Selective breeding for enhanced feed efficiency in aquaculture production has so far been performed indirectly, largely through selection for an improved growth rate. However, a substantial fraction of the genetic variation in feed efficiency is due to other factors than growth, and there is room for improvement. Direct selection for improved feed efficiency would be beneficial. This requires both individual growth and feed intake routinely recorded for a large number of individuals. Recording of individual feed intake in fish is, however, extremely challenging. Hence, the overall aim of this study was to identify novel phenotypes that can be used as indicators for individual feed efficiency in fish breeding. Stable isotopes enhance the ability to trace the processes involved in metabolic breakdown and growth of new tissue that occurs after a dietary switch between diets that differ in their isotope profiles. In one experiment with full-sib families kept in separate tanks and feed efficiency recorded on a tank level, growth rate and sampling day explained 62% of the between-tank variation in feed efficiency, and by extending the regression model with change in isotope profiles, the model was able to explain as much as 79% of this variation. This thesis proposes several new indicator traits with potential for large-scale evaluation of feed efficiency. By the use of stable-isotope profiling, indicator ratio traits for feed efficiency were defined as the ratios between growth and changes in the amount of isotope (nitrogen or carbon). These ratios were estimated with rather low heritabilities (0.06-0.11), but with genetic correlations to feed efficiency on a tank level approaching unity. Feed efficient fish are characterized by low maintenance costs and apparently high carbon metabolism in the liver. The underlying causative genes are still unknown, but several single-nucleotide polymorphisms were found to significantly associate with growth as well as nitrogen and carbon metabolism in the muscle and liver. Furthermore, individual digestibility was found to be heritable with an unfavorable genetic correlation to growth. Based on the findings of the thesis, it can be concluded that indicator traits based on stable-isotope profiling can be used to assess individual phenotypes for feed efficiency that has a potential in selective breeding programs. However, to be commercially relevant, implementing isotope-based indicator traits in selective breeding requires that large quantities of feeds of contrasting isotope profiles can be produced cost-effectively. Individual indicator phenotypes for feed efficiency might be costly to record, but the potential financial benefit for the aquaculture industry is significant.The Foods of Norway project AquaGe

Isotope fractionation in juvenile and large rainbow trout (Oncorhynchus mykiss): Repeatability of stable isotope measures and their relationship to growth rate

publishedVersio

Indications of a negative genetic association between growth and digestibility in juvenile Atlantic salmon (Salmo salar)

acceptedVersio

Verifying the relationship between δ¹³C isotope profile variables and individual feed conversion ratio in large rainbow trout (Oncorhynchus mykiss)

publishedVersio

δ13C in muscle, liver, and adipose fin and their relationship to weight change during both growth and starvation in rainbow trout (Oncorhynchus mykiss), after feeding a diet low in 13C

publishedVersio

Sustainable development in circular agriculture: An illustrative bee↺legume↺poultry example

publishedVersio

Diet effects on the pH-value and SCFA-concentration in the caecum and insulin and glucose values in the blood of horses

Det har de siste årene vært et stort fokus på rasjonens effekt på hestens helse og prestasjon. Det er klare indikasjoner på at det er store fordeler med å gi mer fiber i forhold til sukker og stivelse i rasjonen til hest. En forståelse for hvordan stivelse og fiber fordøyes og hvordan endeproduktene omsettes i kroppen hos hest er essensielt, for å kunne utvikle fôrrasjoner som hindre utvikling av fôringsrelaterte helseproblemer. Formålet med oppgaven var derfor å se på fordøyeligheten til ulike fôrråvarer i fôrrasjonen til blindtarmsfistulerte hester og hvordan rasjonene påvirket glukose og insulin i blodet og pH-verdien og VFA-konsentrasjonen i blindtarmen. Endring i pH-verdi, VFA-konsentrasjon i blindtarmen og insulin og glukose i blodet ble sammenlignet for å undersøke effekten av fôrrasjon på hestens insulin- og glukoseverdier i blodet og gjæringsforløpet i blindtarmen. Studiet brukte fire blindtarmsfistulerte hester og tarm- og blodprøvene ble tatt opptil 8 timer etter fôring. Det ble gjort totaloppsamling av gjødsel i 4 døgn for å finne fôrråvarenes apparente total fordøyelighet. Hestene ble gitt fire forskjellige fôrrasjoner (høyrasjon, byggrasjon, lusernerasjon, eplepulprasjon) i fire perioder. Det førte til signifikante forskjeller mellom rasjonenes påvirkning på insulin og glukose. Byggrasjonen hadde størst påvirkning på insulinverdiene, men høyrasjonen hadde størst svingninger i glukosekonsentrasjonen. Det viser at ved lite glukose i blodet vil leverglykogen brytes ned og pumpes ut i blodet. Det fører til store svingninger i blodet som ikke er å foretrekke hos hest. Byggrasjonen hadde størst påvirkning på pH-verdien i blindtarmen, som skyldes fermentering av stivelse i blindtarmen. pH-verdien falt imidlertid ikke så lavt som tidligere målt og det konkluderes med at 1,4 g stivelse/per kg kroppsvekt er en akseptabel mengde i en fôrrasjon. Det ble videre målt forskjeller i påvirkning på gjæringsforløpet i blindtarmen, men forskjellene skyldes i all hovedsak passasjehastigheten i tarmen. Dette studiet gir et grunnlag for forståelse for hvordan enkelte fôrråvarer påvirker pH-verdien og gjæringsforløpet i blindtarmen og insulin- og glukoseverdiene i blodet.M-H

Individual phenotyping of feed efficiency in lambs fed stable isotopes through maize silage

Recording feed intake and thus feed efficiency in ruminants is challenging. Hence, there is a need to establish indicator traits that can capture the individual variation in feed efficiency, without requiring individual feed intake recordings. This study aimed to explore whether the methodology established in salmon using individual indicator traits for feed efficiency based on stable isotope profiling could be transferred to lambs since the product for both species is meat. We used a total mixed ration based on maize silage to record the individual indicator traits for feed efficiency. The experiment was done with twelve weaned female lambs of the Norwegian White Sheep grouped equally in three, one group fed a total mixed ration enriched with 13C for 42 days, the second group grazed for 21 days and then fed the total mixed ration for 21 days, and the third group grazed for 42 days. The latter group was included to establish a baseline value for the stable isotope percentage in the back and thigh muscle tissues. Recording of 13C in the back muscle of the animals in the first two groups, resulted in a phenotypic correlation as large as 0.92 between individual feed conversion ratio and the individual indicator traits for feed efficiency based on stable isotope profiling. An assessment through individual indicator traits would be independent of the recording of individual feed intake.acceptedVersio

Stable isotope profiling for large-scale evaluation of feed efficiency in Atlantic salmon (Salmo salar)

acceptedVersio

Association of gut microbiota with metabolism in juvenile Atlantic salmon

The gut microbiome plays a key role in animal health and metabolism through the intricate functional interconnection between the feed, gut microbes, and the host. Unfortunately, in aquaculture, the links between gut microbes and fish genetics and production phenotypes are not well understood. In this study, we investigate the associations between gut microbial communities, fish feed conversion, and fish genetics in the domestic Atlantic salmon. Microbial community composition was determined for 230 juvenile fish from 23 full-sib families and was then regressed on growth, carbon and nitrogen metabolism, and feed efficiency. We only found weak associations between host genetics and microbial composition. However, we did identify significant (p < 0.05) associations between the abundance of three microbial operational taxonomical units (OTUs) and fish metabolism phenotypes. Two OTUs were associated with both carbon metabolism in adipose tissue and feed efficiency, while a third OTU was associated with weight gain