ConcIuding remar£cs
97
flowing from nearer basine, other possible nutrient inputs have to be taken
into account.
This nutrient inflow capable of participating in the satisfaction of
dietary requirements of pond fish directly or indirectly would eventually
modify their apparent nutrient needs. Although, use of organic fertilizers
by man is by far the most important indirect source of feed, the dietary
role of bacteria adhered to the ingested particles remains to be known. The
direct or indirect role of bacteria in the feeding of fish cultivated in
ponds requires futher analysis. lt remains nevertheless true that one of the
major problems is the respective roles of natural and elaborate complemen—
tary diets.
Nutrient utilization and need focused on the absorption efficiency of
herbivorous cyprinids which could be improved by microbial inoculation. In
higher vertebrates the role of digestive flora is appreciable and Luquet
suggested that current knowledge of digestive flora indicates that in fish
the nutritional role would be meager.
Some recent work has
shown that the
microflora have very low cellulase activity, and do not appreciable amounts
of amino acids to the growth of fish. Two questions arose on
techniques to
measure
the microbial activity in fish intestines, and why the levels in
most
hilios are so low since the minimal values found in homeotherms are
appreciably higher, and in these animals contribute to the metabolism of feed
components.
Compensatory mechanisms are not well known in fish, and Matty
presented the idea of natural bacterial input and the role these bacteria
might play in protein utilization. Some Russian research has indicated that
the potential citizivy of the indispensable amino acids by bacteria in cypri—
nid gut does contribute to the nutrient requirements of the species, and in
addition dietary non—protein nitrogen in the form of urea does increase the
level and activities of these bacteria.
The potential use of growth hormones was discussed by Pullin who sug—
gested the practical application of endocrinology to improved growth and
better fish culture.
Commercial application of microbiologically synthesized
growth hormone appears to be on the horizon. Halver cited the persistant
efforts in genetic engineering of chum salmon growth hormone that have led
to
commercial production of this compound in Japan. Concern was expressed by
Hepher, who suggested that natural growth would be more than sufficient to
provide economical response, and that more éffort should be made to reduce
the high cost proteins in the diet and to reduce other production costs,
and to
increase yields of fish per unit area. He suggested that more gains
might be obtained through hormonal manipulation of protein metabolism, and
consequently efficient protein utilization. Other conferees expressed inte—
rest
in the possible application and the direct beneficial effects of the
use
of growth hormone in various species.
The conferees
felt that distinction should be made between monoculture
and polyculture strategies_in fish husbandry. Neither specific nutrient needs
noi specific feed formulations are known for all the strategies used. A tre—
mendous
amount
of research remains to be done. Horvath pointed out that all
supplemental feeds appear to have similar performance in pond fish culture.
He suggested more emphasis should be placed on natural trophic input, and
the impact upon,the formulations for supplemental feeds.
Methodology in fish nutrition and fish physiology requires refinement.
Some conferees considered gut contents but do not measure the abundance of
natural feed organisms. When specific nutrient requirements are known, then
good diets can be formulated from corresponding feedstuffs. When one knows
the dietary composition, one can learn much from various feed composition
feeding trials, or understand results of a diet of simular comp051t10n under
different feeding conditions.
97
flowing from nearer basine, other possible nutrient inputs have to be taken
into account.
This nutrient inflow capable of participating in the satisfaction of
dietary requirements of pond fish directly or indirectly would eventually
modify their apparent nutrient needs. Although, use of organic fertilizers
by man is by far the most important indirect source of feed, the dietary
role of bacteria adhered to the ingested particles remains to be known. The
direct or indirect role of bacteria in the feeding of fish cultivated in
ponds requires futher analysis. lt remains nevertheless true that one of the
major problems is the respective roles of natural and elaborate complemen—
tary diets.
Nutrient utilization and need focused on the absorption efficiency of
herbivorous cyprinids which could be improved by microbial inoculation. In
higher vertebrates the role of digestive flora is appreciable and Luquet
suggested that current knowledge of digestive flora indicates that in fish
the nutritional role would be meager.
Some recent work has
shown that the
microflora have very low cellulase activity, and do not appreciable amounts
of amino acids to the growth of fish. Two questions arose on
techniques to
measure
the microbial activity in fish intestines, and why the levels in
most
hilios are so low since the minimal values found in homeotherms are
appreciably higher, and in these animals contribute to the metabolism of feed
components.
Compensatory mechanisms are not well known in fish, and Matty
presented the idea of natural bacterial input and the role these bacteria
might play in protein utilization. Some Russian research has indicated that
the potential citizivy of the indispensable amino acids by bacteria in cypri—
nid gut does contribute to the nutrient requirements of the species, and in
addition dietary non—protein nitrogen in the form of urea does increase the
level and activities of these bacteria.
The potential use of growth hormones was discussed by Pullin who sug—
gested the practical application of endocrinology to improved growth and
better fish culture.
Commercial application of microbiologically synthesized
growth hormone appears to be on the horizon. Halver cited the persistant
efforts in genetic engineering of chum salmon growth hormone that have led
to
commercial production of this compound in Japan. Concern was expressed by
Hepher, who suggested that natural growth would be more than sufficient to
provide economical response, and that more éffort should be made to reduce
the high cost proteins in the diet and to reduce other production costs,
and to
increase yields of fish per unit area. He suggested that more gains
might be obtained through hormonal manipulation of protein metabolism, and
consequently efficient protein utilization. Other conferees expressed inte—
rest
in the possible application and the direct beneficial effects of the
use
of growth hormone in various species.
The conferees
felt that distinction should be made between monoculture
and polyculture strategies_in fish husbandry. Neither specific nutrient needs
noi specific feed formulations are known for all the strategies used. A tre—
mendous
amount
of research remains to be done. Horvath pointed out that all
supplemental feeds appear to have similar performance in pond fish culture.
He suggested more emphasis should be placed on natural trophic input, and
the impact upon,the formulations for supplemental feeds.
Methodology in fish nutrition and fish physiology requires refinement.
Some conferees considered gut contents but do not measure the abundance of
natural feed organisms. When specific nutrient requirements are known, then
good diets can be formulated from corresponding feedstuffs. When one knows
the dietary composition, one can learn much from various feed composition
feeding trials, or understand results of a diet of simular comp051t10n under
different feeding conditions.