Methodological aspects of evaluating nutritive values of fish feed ingredients

• Applicant: Professorin Dr. Gudrun Brockmann, since 4/2017
• Subject Area: Animal Breeding, Animal Nutrition, Animal Husbandry
• Term: from 2013 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 251283869

Accurate assessment of nutritive values of feed ingredients is important for formulating nutritional adequate and cost-effective fish feeds. However, there is a significant knowledge gap about the methodology for estimating nutritive values of fish feed ingredients. To date aquaculture feed evaluation has relied on apparent digestibility coefficients. A single-level assay of mixing 70% reference diet with 30% test ingredients is the common protocol to estimate apparent digestibility of fish feed ingredients. Despite its wide usage, the single-level assay is only valid when there are no interactions between the reference diet and the test ingredients. When interactions exist, a multi-level assay involving three or more substitution rates of test ingredients should be used. Factors contributing to such interactions should be examined systematically so that the appropriate methodology for evaluating digestibility of fish feed ingredients can be developed.True digestibility coefficients and bioavailability values are not routinely adopted in aquaculture feed evaluation. A linear regression method has recently been developed to account for endogenous losses and to obtain true digestibility for farm animals. This method could facilitate the adoption of true digestibility in fish feed evaluation but remains to be tested. Furthermore, corroboration of digestibility and bioavailability values could lead to more accurate evaluation of nutritive value of feed ingredients in that bioavailability estimates from slope ratio assays offer direct assessment of the part of nutrient that is metabolically available to animals. However, slope ratio growth trials involve more research effort and time than digestibility trials. It is thus necessary to investigate whether bioavailability values can be inferred from digestibility coefficients for fish. Therefore, this project aims to investigate the methodological aspects of evaluating nutritive values of fish feed ingredients. Specifically, this projects aims to compare the accuracy of nutrient digestibility estimates between the multi-level assay and the single-level assay by examining influencing factors including type of basal diet, type of ingredients, and inclusion level of ingredients. Furthermore, this project will estimate true protein digestibility of ingredients by employing the linear regression approach and estimate bioavailability by conducting a slope ratio assay. Inference between true digestibility coefficients and bioavailability estimates will be made. In addition, this project will investigate and quantify the digestibility and utilization of different types and levels of dietary starches for omnivorous fish species. Finally, the information generated from the feeding trials will be used to develop mechanistic models to estimate protein digestibility and starch digestibility.

• DFG Programme: Research Grants
• Ehemalige Antragstellerin: Professorin Dr. Katheline Hua, until 3/2017