In 1951 Dr John E Halver of the School of Fisheries Science, University of Washington, USA presented the ‘model semi-purified fish diet’ to the aquatic nutrition research community. This innovation allowed for the proliferation of deficiency studies with mainly salmonid fish such as rainbow trout and Pacific salmon to evaluate the significance of vitamins in complete diets for cultured fish.

1. May | June 2013
Niacin: one of the key B vitamins for
sustaining healthy fish growth and
production
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3. I
n 1951 Dr John E Halver of the
School of Fisheries Science, University
of Washington, USA presented the
‘model semi-purified fish diet’ to the
aquatic nutrition research community. This
innovation allowed for the proliferation of
deficiency studies with mainly salmonid fish
such as rainbow trout and Pacific salmon
to evaluate the significance of vitamins in
complete diets for cultured fish.
With such an ‘ideal’ diet, vitamins could
easily be assayed by using this vitamin test
diet, consisting of ‘vitamin free’ carbohydrate
and protein sources i.e. casein, purified gelatin,
potato starch, hydrogenated cotton seed oil,
alpha-cellulose flour, minerals, cod liver oil,
combined with crystalline vitamins. Each vita-
min could then be systematically assessed by
selective exclusion from this advanced basal
diet formulation. The water soluble vitamins
such as the B-complex and especially vitamin
C (ascorbate) were all found to be essential
in fish as in other terrestrial animals of com-
mercial importance and indeed having the
same basic functions as in humans.
The role of niacin (vitamin B3) is no
less important within aquatic species; as fish
farming became more prevalent, the health
status of stocks fluctu-
ated due to the wide
spectrum of feed for-
mulations at that time.
A number of nega-
tive symptoms were
attributed to niacin
deficiency and steps
were taken to protect
against them based on
early evidence.
In the 1940s and
1950s fish were found
to have a loss of appetite and poor food
conversion (food intake to body weight ratio)
that progressed into a darker skin colour,
anorexia, posterior gut lesions, oedema of
the stomach and intestine, erratic motion and
at-rest muscle spasms. In the late 1950s and
1960s, a predilection to sunburn in fish was
discovered and, in carp, subcutaneous haem-
orrhages developed under chronic and acute
niacin deficiency.
In the 1970s, eels were found to develop
skin lesions and display erratic swimming,
while lesions, deformed jaws, and anaemia
were discovered in catfish, Ictalarus punctatus.
The period from 1980 to date encompassed
a series of investigations that augments earlier
knowledge, but there have been relatively few
studies in the early 21st century except for the
work of Shaik Mohammed et al. (2001) where
pathological effects of niacin deficiency similar
to this described above were reported from
studies with Indian catfish (Heteropneustes
fossilis).
Metabolic considerations
Exogenous proteins within the diet supply
the metabolic pool with essential and non-
essential amino acids. Among these is tryp-
tophan which has considerable importance in
fish nutrition. In mammals, there is a recog-
nised and documented conversion pathway
from tryptophan to niacin, thus allowing tryp-
tophan, and proteins rich in tryptophan, to be
an important reservoir for niacin biosynthesis.
Although the essential amino acid tryp-
tophan is a precursor of niacin, this endog-
enous synthesis, comprising 13 steps in a
metabolic sequence is not deemed efficient.
Studies in man have shown that approximately
60 mg of tryptophan are required to produce
1 mg of niacin and this ratio varies consider-
ably within different vertebrate groups.
Fish, however, may even lack this conver-
sion capacity or have very a poor efficacy for
this metabolic pathway. By supplementing
both a niacin deficient and niacin complete
diet with varying amounts of tryptophan, it
was previously determined that tryptophan
levels have no effect on niacin accumulation.
Serrano and Nagayama (1991) found that the
3-hydroxyanthranilic acid (3-HAA) to picolinic
acid carbolase (PC) activity ratio in rainbow
trout suggested an ineffective conversion from
tryptophan to niacin. This finding will help
explain higher niacin requirements for some
fish, as others do carry the capacity in some
degree but this cannot be an insurance against
providing a separate dietary supply. Niacin
and niacinamide
are required by
all living cells
and their chemi-
cal structure
is depicted in
Figure 1.
They are
essential com-
ponents of two
coenzymes,
niacinamide
adenine dinucle-
Niacin: one of the key B
vitamins for sustaining healthy
fish growth and production
by Simon J Davies and Mark Rawling, Aquaculture Nutrition & Health Group, Plymouth
University, United Kingdom
Nicotinic Acid Nicotinamide
Figure 1: Niacin in its two biologically active forms as presented to fish for assimilation
20 | InternatIonal AquAFeed | May-June 2013
FEATURE

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5. otide (NAD), and niacinamide adenine dinu-
cleotide phosphate (NADP) that are involved
in numerous enzymatic pathways especially
those involving energy mediation and protein
synthesis and degradation. More than 40
biochemical reactions have been identified
as being dependent on these coenzymes as
co-factors. Their major function is the removal
of hydrogen from specific substrates and the
transfer of hydrogen to another coenzyme.
Reactions in which NAD and NADP are
involved include the metabolism of carbohy-
drates, lipids and proteins at the cross roads
of metabolism and vital for energy production
from these nutrients and protein turnover.
With respect to genomic stability, the
need for niacin seems most imminent when
the organism is under genotoxic or oxida-
tive stress, with particular reference to UV
exposure of the animal (Hageman & Stierum,
2001). A deficiency of niacin will result in an
increase or disrepair of DNA nicks within
chromosomes, and consequent increase in
chromosomal breakage, and a heightened
sensitivity to mutagens (Fenech, 2002). In
general, fish with niacin deficiencies displayed
an increased risk of sunburn when under even
natural UV radiation.
In the expanding aquaculture industry,
feed conversion ratios must
be optimised in order for
production costs to be min-
imised. Greater efficiency
present throughout cultur-
ing conditions will lead to
shorter growing time and a
greater demand for micro-
nutrients such as vitamins.
Surplus nutrients, such as
vitamins supplied above lev-
els useful to the species, can
be removed from the diet if
exact requirements are met.
In the past, many vitamins
have been included in excess
of recommended levels to be
certain that the requirements
were fully complied (NRC
2011). However, studies have
reported excess niacin can inhibit growth
(Poston & Lorenzo, 1973; Poston & Combs,
1980); conversely, sub-optimal absorption of
nutrients can be avoided if requirements are
correctly defined and adequately presented
in feed. For maximal efficiency of production,
target provisions of all essential nutrients, as
specified through research, must be provided
through additional mineral and vitamin sup-
plementation. If levels are unknown, further
research is needed to clarify the degree of
vitamin fortification necessary to maintain
health and production for all phases of rearing
and conditions.
In relation to the other water-soluble
vitamins, niacin requirements in fish procure
a ranking amongst the highest needs, with
the exception of choline (NRC, 2011). While
many other vitamins are synthesised from
precursor compounds obtained through feed
ingredients, in aquatic animals, niacin is usually
obtained solely through niacin presented in
the diet.
Niacin requirements
Caution must be expressed due to the
variety of methodological approaches used
in ascertaining vitamin requirement levels. In
many cases, age and genetic strain of the spe-
cies varies together with the pre-nutritional
history of the aquatic animal under investiga-
tion. In particular, the nature of the carbohy-
drate component employed in experimental
diets is not fully reported in the scientific
literature. For example, it is well known that
the carbohydrate level and complexity may
influence the requirement of niacin in terms
of processing of dietary energy (Shiau & Suen,
1992). This may be evident when raw materi-
als are subjected to extrusion processing in
which carbohydrates such as starch in cereals
may undergo gelatinisation yielding dextrin
and thereby increasing the digestible energy
value of the carbohydrate fraction. It was
found that for hybrid tilapia that the niacin
requirements for fish fed glucose or dextrin as
the carbohydrate energy source was 26 and
125 mg/Kg diet respectively.
Previous formulations of fish diets often
failed to address the true bioavailability of
micronutrients present in fish feed ingredients
pursuant to a limited common database
describing this knowledge. The general niacin
requirements for different species are shown
in Figure 2 and these vary considerably
depending on many factors. Dietary require-
ments have been reported to range from just
1-5 mg per kg of feed for rainbow trout to
150-200 mg for pacific salmon and 14 mg per
kg for channel catfish.
Clearly much will depend on the carnivo-
rous, omnivorous or herbivorous nature of
the fish species in question and rearing condi-
tions. Investigations on Gilthead sea bream
(Sparus aurata) by Morris and Davies (1995)
and by Morris et al. (1995), where the quali-
tative and quantitative requirements for this
important marine fish were first established
using semi-purified diet ingredients similar to
the Halver concept.
The minimum nicotinic acid requirement
for sea bream was determined to be 52 mg/
Kg to achieve optimum growth performance
and 25 mg/kg for normal haematological bal-
ance and liver to body weight ratio.
In 1997, Shiau reported parallelism
between the niacin requirement of warm
water fish and a varying source of dietary
Figure 2: Niacin requirements for selected aquatic
animal species (from compiled literature sources)
May-June 2013 | InternatIonal AquAFeed | 21
FEATURE
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6. carbohydrate. In general, certain warm
water fish, namely carnivorous species, uti-
lise dietary carbohydrate poorly and it
is recognised that carbohydrate obtained
from different sources may not be equally
available to all fish of the same species.
There is merit for consideration of the
changes in protein level, quality, and protein
to energy ratio for optimum vitamin levels
to be recommended. Modern fish diets are
much higher in energy, presented as oil for
carnivorous fish, whilst carbohydrate in the
form of starch is quite acceptable for omni-
vores such as tilapia and carp. Niacin is given
special importance in this area due to its
relevancy in the metabolism of protein and
the release of energy from these nutrients
as stated previously.
However implications towards dietary
requirement and variability, warrants a need
to establish additional scientific information
regarding the digestibility of niacin and sub-
sequent availability coefficients within varying
diets formulations based on practical ingre-
dients.
From the data of Ng et al. (1998), it was
suggested that niacin supplementation can be
reduced to a more efficient level due to the
relatively high amount of biologically available
niacin found in typical feed ingredients used
in modern fish feed formulations. However,
the provisions may not be adequate to
meet current safety margins to guarantee
production and health criteria for all spe-
cies. Also, the inability to utilise particular
fish feeds due to varying dietary constraints
would justify continued supplementation and
refinement. In addition, it was found that the
bioavailability of niacin increased by some
57 percent when corn meal was extrusion
cooked rather than administered in the
diet in its native form. This suggests that
processing technology is an important area
for further investigation for determining the
optimum inclusion levels of niacin for a range
of aquatic species.
Stability and processing losses
Niacin is regarded as a highly stable vitamin
in animal nutrition and is usually added to
feed as nicotinic acid or nicotinamide within
the vitamin premix formulations within a dry
mixture with a carrier material along with
other vitamins and possibly mineral supple-
ments as well.
The advent of high energy and nutrient
dense feeds in many countries engaged in
intensive fish farming operations has also
placed a higher burden on maintaining the
health of fish, whilst promoting faster growth
rates and efficient feed utilisation. The use
of expanded and extruded feeds offer more
scope in feeding management but may greatly
influence the levels of vitamins available to
fish under various conditions. Extrusion of
diets has the tendency to reduce the activity
of vitamins especially those within the water
soluble class and the processing of raw materi-
als may lead to serious losses. Generally this is
in the order of 10-20 percent for most vita-
mins reported (Tacon, 1985, Gabaudan and
Hardy, 2000). Further reductions are caused
by storage of pelleted feed and this may result
in impairment to fish health and production
efficiency over extended time.
Future perspective
Indeed, the movement towards new fish
species in aquaculture such as flounders;
turbot, sole and halibut as well as sea bass
and sea bream in Europe, cobia in the
USA and Brazil have generated considerable
interest in producing specific diets that can
meet their individual requirements for growth,
development and health. Much is known
about the gross nutritional requirements of
these emerging species but little on vitamins,
especially niacin. Intensive rearing conditions
(i.e. UV light exposure to outdoor pens)
and husbandry related factors may adversely
affect the physiological status of fish and
induce metabolic stress causing tissue dam-
age and impaired performance. The potential
of niacin supplementation in reducing such
effects could prove a valuable area for future
investigation.
22 | InternatIonal AquAFeed | May-June 2013
FEATURE

7. It is evident that the vitamin requirements
of fish are subject to numerous factors.
Recent advances in our understanding of
aquatic animal biochemistry and physiology
together with aquafeed technology increase
the advantageous value of a thorough re-
examination of the vitamin requirements of
fish. This is particularly pertinent for niacin
given its role in aquatic animal nutrition. There
is a paucity of information in the literature for
niacin in fish compared to other vitamins, and
this matter needs to be addressed in the light
of new candidate species for aquaculture and
changing feed formulations where plant by
products are increasingly being incorporated.
Selected References
Fenech, M. (2002). “Genomic Stability: a new
paradigm for recommended dietary allowances
(RDA’s).” Food and Chemical Toxicology. vol. 40. pp
1113-1117.
Gaubadan, J and Hardy R. W. (2000). Vitamin
sources for fish feeds pp, 961-965 In Encyclopaedia
for Aquaculture, R. R. Stickney, Editor, New York,
John Wiley and Sons, Inc.
Hageman, G.J. and Stierum, R.H. (2001). “Niacin,
poly (ADP-ribose) polymerase-1 and genomic
stability.” Mutation Research. – Fundamental and
Molecular Mechanisms of Mutation. vol 475. nos
1-2. pp 45-56.
Halver, J.E. (1957). “Nutrition of salmonid fishes: 3.
Water-soluble vitamin requirements of Chinook
salmon.” Journal of Nutrition. vol. 62. pp. 225-43.
Halver, J.E., (Halver, J.E. and Hardy, R.W. (Editors).
Fish Nutrition. 3rd Edition. Oxford: Academic Press,
2002.
Morris, P.C. and Davies, S.J. (1995) The requirement
of the gilthead sea bream (Sparus aurata L). for
nicotinic acid. Animal Science, 61: 437-443
Morris, P.C. Davies, S.J. and Lowe, D.M. (1995)
Qualitative requirements for B vitamin in diets for the
gilthead sea bream (Sparus aurata) Animal Science,
61; 419-426.
Ng, W.K, Serrini, G., Zhang, Z and Wilson, R.P.
(1997) “Niacin requirement and inability of
tryptophan to act as a precursor of NAD+ in
channel catfish, Ictalurus punctatus” Aquaculture. vol.
154. nos. 1-4. pp 273-285.
NRC (2011) “Nutrient Requirements of Fish,”
NAS/NRC, Academic Press, Washington D.C.
Poston, H.A. (1969) “The effect of excess levels of niacin
on the lipid metabolism of fingerling brook trout.” In:
Fisheries Research Bulletin, Albany, N.Y.: State of New York
Conservation Department. no. 32. pp. 9-12.
Poston, H.A. and DiLorenzo, R.N. (1973)
“Tryptophan conversion to niacin in the brook
trout (Salvelinus pontinalis).” Proceedings. Society
for Experimental Biology and Medicine. vol. 140.
pp. 110-12.
Poston, H.A. and Combs, G.F. (1980) “Nutritional
implications of tryptophan catabolising enzymes in
several species of trout of salmon,” Proceedings.
Society for Experimental Biology and Medicine. vol.
163. pp. 452-454.
Poston, H.A., and Wolfe, M.J. (1985). “Niacin
requirement for optimum growth, feed conversion
and protection of rainbow trout, Salmo gairdneri
from ultraviolet-B irradiation” Journal of Fish
Diseases. vol 8. no. 5. pp. 451-460.
Serrano, A.E. and Nagayama, F. (1991). “Liver
3-hyroxyanthranilic acid oxygenase activity in
rainbow-trout (Oncorhynchus-mykiss).” Comparative
Biochemistry and Physiology B-Biochemistry &
Molecular Biology. vol. 99. no. 2. pp. 275-280.
Shaik Mohammed, and Ibrahim, A. (2001)
Quantifying the niacin requirement of the Indian
catfish (Heteropneustes fossilis) (Bloch), fingerlings,
Aquaculture Research, 32: 157-162.
Shiau, S.Y., and Suen, G.S. (1992) “Estimation of the niacin
requirements for tilapia fed diets containing glucose or
dextrin.” Journal of Nutrition. vol .122. no. 10. pp. 2030-6.
Tacon, A.G.J. (1985) Nutritional fish pathology:
morphological signs of nutrient deficiency and
toxicity in farmed fish.” Aquaculture Development
and Coordination Programme. ADCP/REP/85/22.
More InforMatIon:
Email: simond@aquafeed.co.uk
Website: http://www.plymouth.ac.uk/pages/view.
asp?page=32557
May-June 2013 | InternatIonal AquAFeed | 23
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Niacin
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