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Utilization of Australian grain legumes by salmonids


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Farhangi, Mehrdad 2003 , 'Utilization of Australian grain legumes by salmonids', PhD thesis, University of Tasmania.

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A large range of ingredients have been considered as potential replacements for
fish meal but grain legumes have attracted most attention in the past. The main
factors that limit the use of grain legumes in animal diets are the number of
antinutritional factors (ANFs) that may adversely affect animal performance. Due
to the high sensitivity of salmonids to ANFs and the importance of salmonid
production in Australia, salmonids have been used as reliable biological tools for
screening the most suitable Australian grain legumes.
In this study, the four most abundant Australian grain legumes: chick peas, faba
bean, field peas and lupin were targeted as potential alternatives to fish meal in
salmonid diets. Chemical, biological and immunological measurements were used
to assess their relative performance. The suitability of the four grains (raw and
processed) was tested with rainbow trout and the effects of body weight (small,
medium and large) and adaptation period on nutrient digestibility were evaluated.
Maximum inclusion of the most suitable grain legume (lupin) was determined and
the effects of exogenous enzymes on the nutrient utilization and fish performance
were also investigated.
The chemical composition and the digestibility of nutrients in lupin were most
suited for rainbow trout compared with the other three grains. Also the
concentrations of the two most important ANFs (trypsin inhibitor and phytic acid)
were lowest in lupin. The concentration of trypsin inhibitor significantly decreased
follwing the combination of both soaking and heating the grains. Fish body size did
not affect nutrient digestibility of the grains. Over the adaptation period in vivo dry
matter digestibility improved only for small fish size and in vivo crude protein
digestibility increased for small and medium fish size. In addition, during the
adaptation period in vivo crude protein digestibility was improved for the grains
that contained higher trypsin inhibition (chick pea and field pea). There was a poor
correlation relationship between in vitro and in vivo digestibility for processed
grains, however there was a significant relationship for the raw grains.
Lupin was selected as the most promising grain legume and the subject of further experiments. Due to the high concentration of neutral detergent fibre (NDF) and
relatively low protein content of the whole grain, dehulling was applied to reduce
the NDF and increase the protein content. A dose response experiment was
conducted to establish the highest possible inclusion level of dehulled lupin (DL) in
rainbow trout diets. Fish performed well at up to 40% inclusion of DL in the diet.
However, growth and the energy efficiency ratio significantly decreased at 50%
inclusion of DL. It was concluded that the fish were unable to effectively utilize the
non-protein energy content of DL at this level of inclusion. Supplementation of the
diets that contained 50% DL with different exogenous enzymes: EnergexTm, Biofeed
plusTM and Alpha galactosidaseTm (separate or in a mixture) did not improve
energy utilization by fish. Surprisingly, the growth performance of the fish that
received 50% DL in the diet was marginally better than the group of fish that
received a fish meal based diet. This was partly related to higher feed intake (ad lib
vs set ration), but significantly better energy efficiency ratio suggested improved
use of the carbohydrate fraction of the lupin. The DL that was used in the two
experiments was from the same source but it had been stored under suitable
conditions for about nine months.
Having established the suitability of DL at 50% inclusion level in the rainbow trout
diet, the potential of DL as a fish meal replacement was tested for Atlantic salmon.
The effect of feeding at the most suitable time, based on the diel rhythm of feed
intake on nutrient utilization and growth performance was tested when the fish
received the diets that contained 30% DL. Fish were fed with the diets that
contained 40% and 45% crude protein both in the morning and in the afternoon or
diets that contained 40% crude protein in the morning and 45% crude protein in the
afternoon (mixed diets) and vise versa. Results did not show any effect of feeding
time on nutrient utilization. However, the growth of fish that received the mixed
diets was comparable to groups that received 45% crude protein diets.
The suitability of DL as a fish meal replacement for both rainbow trout and
Atlantic salmon was shown in the current study. Additional studies are needed to
improve the energy utilization and to minimize the dry matter waste of the diets
that contain high levels of DL.

Item Type: Thesis - PhD
Authors/Creators:Farhangi, Mehrdad
Keywords: Grain as feed, Salmonidae, Salmonidae
Copyright Holders: The Author
Copyright Information:

Copyright 2003 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (PhD. )--University of Tasmania, 2003. Includes bibliographical references

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