February 28 - 2018
Adaptation of rainbow trout genotypes to simultaneous changes in multiple plant-based diet ingredients
A Kause, M Janhunen, A Nousiainen, H Koskinen, J Koskela (Natural Resources Institute Finland, Luke)
Feed composition is one of the fastest changing environmental factors for farmed fish. For carnivorous fish like Atlantic salmon, European seabass, gilthead seabream, rainbow trout and turbot, fishmeal produced from wild-caught small pelagic fish species is considered as the superior protein source in feeds. Due to the depletion of wild fish populations and the consequent economical and environmental pressure, feed companies have replaced a major part of fishmeal with protein of plant-origin. The number of potential plant protein sources for farmed fish is large, and most nutritional research has focused on ingredients with security of supply, such as soybeans, wheat, corn and pea. However, some genotypes or fish strains may be less capable of adapting to these novel diets with protein of plant-origin.
Selective breeding makes fish adapted to novel diets
FISHBOOST results on one-year old rainbow trout show that indeed sires differ in their sensitivity to cope with challenging diets. Nevertheless, breeding programmes selecting for fish performance on the current on-growing feeds will make rainbow trout better adapted to the future feeds that use even more plant-protein concentrates to replace fish meal. With the availability of genetic variation and the limited amount of adverse genotype-by-diet interactions in rainbow trout, breeding programmes are aided to make fish more adapted to the novel feeds.
Plant-based ingredients compromise fish performance
Although the genotype-by-diet interactions are generally not of concern, there is high pressure to improve fish performance and welfare specifically on the new plant-based diets. Fish performance, measured as economically important traits such as growth, feed conversion ratio (FCR) and protein retention efficiency, is compromised when large amounts of plant-protein are added to fish feeds.
The use of a mixture diet design in this study allowed the identification of diet mix combinations that support good fish performance. In contrast to the one-ingredient-at-a-time experiments, interactions between the ingredients could be observed and clearly showed benefits when including several plant protein mixes. Simultaneously the multiple ingredients support fish performance better than on their own, likely because they compensate for each other’s limitations.
Future needs
These results emphasise the further need for genetically improving the feed utilisation traits of rainbow trout on new plant-based feeds, and simultaneously, to tailor-make feeds specifically for the genetically superior farmed fish with their unique nutritional needs.
This FISHBOOST study has linked animal genetics, the main focus on the FISHBOOST project, with the development of novel more sustainable fish feeds. Such information highlights the power of selective breeding to support sustainable development in other areas such as feed development.
--------------------------
Methodology in detail
To assess the degree to which genotypes are adapted to multiple diet ingredients, genetic variation in the sensitivity of one-year-old rainbow trout against multiple diet ingredients was quantified.
Rather than using two alternative diets, rainbow trout were fed with the currently used diet (diet FM with 300 g kg-1 of fish meal), and on a range of commercially potential future diets with decreasing fish meal content. A total of seven different diets were used in which the concentrations of three commercially viable raw material concentrate mixes varied: fish meal (FM), soya protein-wheat gluten concentrate (S-MIX) and pea protein-wheat gluten concentrate (P-MIX).
The implemented mixture diet design to quantify fish responses as a surface along several changing diet ingredient mixes allowed the identification of diet mix combinations that support good fish performance, identified as the area on the response surface at which fish performance is at least 95% of the maximum observed performance. This area identifies any combination of the three ingredient mixes that produces almost the same fish performance.
As expected, fishmeal diet was the most optimal diet supporting high growth for all progenies of sires. However, the progenies of sires differed in the extent of the area with at least 95% of the maximum growth. The fast-growing genotypes on FM diet generally had very small 95% optimal response area, i.e., they were more specialists (Sire 1 in Fig 1.), whereas the slow-growing genotypes on FM diet had much larger 95% area (more generalist genotype) (Sire 10 in Fig. 1).
This is the reflection that there is among-family variation in the sensitivity of rainbow trout to plant protein concentrate mixes, and that the fast growing genotypes have their unique physiological needs for maintaining their high genetic potential.
Adaptation of rainbow trout genotypes to simultaneous changes in multiple plant-based diet ingredients
A Kause, M Janhunen, A Nousiainen, H Koskinen, J Koskela (Natural Resources Institute Finland, Luke)
Feed composition is one of the fastest changing environmental factors for farmed fish. For carnivorous fish like Atlantic salmon, European seabass, gilthead seabream, rainbow trout and turbot, fishmeal produced from wild-caught small pelagic fish species is considered as the superior protein source in feeds. Due to the depletion of wild fish populations and the consequent economical and environmental pressure, feed companies have replaced a major part of fishmeal with protein of plant-origin. The number of potential plant protein sources for farmed fish is large, and most nutritional research has focused on ingredients with security of supply, such as soybeans, wheat, corn and pea. However, some genotypes or fish strains may be less capable of adapting to these novel diets with protein of plant-origin.
Selective breeding makes fish adapted to novel diets
FISHBOOST results on one-year old rainbow trout show that indeed sires differ in their sensitivity to cope with challenging diets. Nevertheless, breeding programmes selecting for fish performance on the current on-growing feeds will make rainbow trout better adapted to the future feeds that use even more plant-protein concentrates to replace fish meal. With the availability of genetic variation and the limited amount of adverse genotype-by-diet interactions in rainbow trout, breeding programmes are aided to make fish more adapted to the novel feeds.
Plant-based ingredients compromise fish performance
Although the genotype-by-diet interactions are generally not of concern, there is high pressure to improve fish performance and welfare specifically on the new plant-based diets. Fish performance, measured as economically important traits such as growth, feed conversion ratio (FCR) and protein retention efficiency, is compromised when large amounts of plant-protein are added to fish feeds.
The use of a mixture diet design in this study allowed the identification of diet mix combinations that support good fish performance. In contrast to the one-ingredient-at-a-time experiments, interactions between the ingredients could be observed and clearly showed benefits when including several plant protein mixes. Simultaneously the multiple ingredients support fish performance better than on their own, likely because they compensate for each other’s limitations.
Future needs
These results emphasise the further need for genetically improving the feed utilisation traits of rainbow trout on new plant-based feeds, and simultaneously, to tailor-make feeds specifically for the genetically superior farmed fish with their unique nutritional needs.
This FISHBOOST study has linked animal genetics, the main focus on the FISHBOOST project, with the development of novel more sustainable fish feeds. Such information highlights the power of selective breeding to support sustainable development in other areas such as feed development.
--------------------------
Methodology in detail
To assess the degree to which genotypes are adapted to multiple diet ingredients, genetic variation in the sensitivity of one-year-old rainbow trout against multiple diet ingredients was quantified.
Rather than using two alternative diets, rainbow trout were fed with the currently used diet (diet FM with 300 g kg-1 of fish meal), and on a range of commercially potential future diets with decreasing fish meal content. A total of seven different diets were used in which the concentrations of three commercially viable raw material concentrate mixes varied: fish meal (FM), soya protein-wheat gluten concentrate (S-MIX) and pea protein-wheat gluten concentrate (P-MIX).
The implemented mixture diet design to quantify fish responses as a surface along several changing diet ingredient mixes allowed the identification of diet mix combinations that support good fish performance, identified as the area on the response surface at which fish performance is at least 95% of the maximum observed performance. This area identifies any combination of the three ingredient mixes that produces almost the same fish performance.
As expected, fishmeal diet was the most optimal diet supporting high growth for all progenies of sires. However, the progenies of sires differed in the extent of the area with at least 95% of the maximum growth. The fast-growing genotypes on FM diet generally had very small 95% optimal response area, i.e., they were more specialists (Sire 1 in Fig 1.), whereas the slow-growing genotypes on FM diet had much larger 95% area (more generalist genotype) (Sire 10 in Fig. 1).
This is the reflection that there is among-family variation in the sensitivity of rainbow trout to plant protein concentrate mixes, and that the fast growing genotypes have their unique physiological needs for maintaining their high genetic potential.
Fig. 1. Tertiary plots showing daily growth coefficient (DGC) as a function of concentrations of fishmeal, pea protein-wheat gluten concentrate-mix, and soy protein-wheat gluten concentrate-mix for the progeny of two extreme sires. The feed component axes are given in percentages of ingredient concentrates. Grey area confine the diet combinations that produces at least 95% of the maximum DGC for each sire. For sire 1 (fast grower), the area with at least 95% DGC is small, yet DGC at 100% FM diet is much higher than DGC for sire 10. For sire 10 (slow grower), the area with at least 95% DGC is large, about 25% of the diet ingredient combinations support high growth.
The mixture diet design aids in determining the most potential combinations of feed ingredient concentrations for practical feed formulae.
The response surfaces produced via the mixture diet design allow dynamic determination of suitable feeds when multiple diet ingredients need to be considered. Production of industrial aquafeeds is a dynamic process in which the amounts of raw materials or their concentrates vary between batches, depending on the availability and price of the ingredients. There is not a single fixed diet formula, but rather many different combinations of several ingredients that can be used to produce a feed with more or less the same proximate feed composition (energy, protein, lipid, carbohydrates).
The mixture diet design aids in determining the most potential combinations of feed ingredient concentrations for practical feed formulae.
The response surfaces produced via the mixture diet design allow dynamic determination of suitable feeds when multiple diet ingredients need to be considered. Production of industrial aquafeeds is a dynamic process in which the amounts of raw materials or their concentrates vary between batches, depending on the availability and price of the ingredients. There is not a single fixed diet formula, but rather many different combinations of several ingredients that can be used to produce a feed with more or less the same proximate feed composition (energy, protein, lipid, carbohydrates).
|
|
The experiment was performed with the families originating from the Finnish national breeding programme for rainbow trout.
In addition to feed utilization, the trait recording included non-destructive measuring of fillet lipid percentage.
In addition to feed utilization, the trait recording included non-destructive measuring of fillet lipid percentage.
