Abstract: The experimental fish Jade perch with initial weight of 4.5g were divided into
three groups, one for 1.25 mg/kg Nosiheptide treatment, one for 2.5 mg/kg Flavomycin treatment,
and one control without supplementation. After feeding periods of 50 days, the length and weight
of fish were examined. Five fish were dissected to test viscera weight in each group, and a piece of
small intestines of fish from the control and the 1.25 mg/kg Nosiheptide treatment was taken for
electronic microscopic observation. The average daily gain of Jade Perch fed with 1.25 mg/kg
Nosiheptide was increased by 7.14% (P<0.05) and 4.65% (P>0.05), respectively, compared with
the control and 2.5 mg/kg Flavomycin treatment. Feed coefficient ratio of fish with 1.25 mg/kg
Nosiheptide treatment is lower than that of the control (P<0.05). There was no significant
difference in viscus ratio and trunk ratio of fish between Nosiheptide treatment and the control
(P>0.05). However, the intestinal villi of fish with 1.25mg/kg Nosiheptide treatment were longer,
more integrated and regular than that of the control. The results suggested that 1.25mg/kg
Nosiheptide could protect the intestinal villi of fish in good order and promote assimilation of
nutriment, therefore increase growth of fish.
Keywords: Nosiheptide, Jade perch, daily gain, feed coefficient ratio, intestinal villi
1. Materials and methods
1.1 Test fish and diets
Fish with the average weight of 4.5g were randomly allotted into three groups, each group
included three replicates. The basal purified diet was formulated (Table 1). Flavomycin and
Nosiheptide were separately added to the basal diet. The diets were prepared by thoroughly mixing
the ingredients and then adding distilled water until a stiff dough was produced. The dough was
then passed through a mincer fitted with a 1.5mm diet and were dried at 25℃ with the aid of an
air-conditioner and an electrical fan. After drying, the diets were broken up, sieved to an
appropriate pellet size and stored at -20℃.
Table 1. Ingredients and nutrient contents of the experimental feed
1.2 Experiment procedure
Jade perch were obtained from farm. Upon the arrival, they were placed in a plastic tank for a
week to acclimate to laboratory conditions. Healthy fish (initial length 3.0~3.5cm) were randomly
divided into three groups. At the beginning of experiment, each of 9 cages (L=2m
×W=1m×H=0.6m) was stocked with fish. Fish were fed three times per day at a feeding rate of 5%
body weight at 7:30, 11:30, and 17:00. The experiment was carried out for 50 days. Every 2 weeks,
the fish were weighed batchly, feed intake recorded and the system cleaned.
Each cage was part of closed recirculating water systems, which had a common reservoir of
water maintained at 26±1℃, pH 7.2 and DO 5mg/L.
At the end of the feeding trial, the weight and length of fish were measured, and viscera of
fish were weighed. Average daily gain, feed conversion ration (feed/gain), condition factor and
viscera ratio were calculated.
1.3 Electron microscopic observation
A clean piece of small intestines, dissected from fish, were obtained by maintaining them in
clean saline solution. Then fixed in cold 2.5% glutaraldehyde, flushed by fixative buffer, postfixed
in 1% osmium tetroxide, flushed by fixative buffer, dehydrated in an ethanol series of 50%, 70%,
80%, 90%, 95% and 100% for 10 minutes, permuted by isoamyl acetate for 30minutes, dried at
critical point. The sections were observed in a transmission electron microscope.
1.4. Statistical analysis
All data measured in the study were analyzed by comparing means according to least
significant difference test, using the procedure of SPSS. A significant level of 0.05 was used.
Values are given as means±SD.
2. Results
2.1 Growth performance
The daily weight gain of fish fed with Nosiheptide, Flavomycin and basal diet was 0.08g, 0.86g,
0.84g, respectively (Table 2). Dietary adding 1.25mg/kg of Nosiheptide could increase the daily
weight gain of fish by 7.14% (P<0.05) and 4.65% (P>0.05), respectively, compared with the
control and the Flavomycin treatment. In contrast to the control, 1.25mg/kg Nosiheptide decreased
the feed efficiency ratio of fish by 2.80% (P<0.05). There was no significant changes were found
in the condition factor and viscera of fish between the three groups (P>0.05).
Table 2. Effects of Antimicrobial peptide on growth of Jade Perch
Notes：Values with different superscripts in the same row are significantly different（P<0.05）.
2.2 Villi of Small Intestine
Intestinal villi of fish fed diet with Nosiheptide developed fully, distributed regularly, and
were similar. The villi of small intestine of fish supplemented with 1.25mg/kg Nosiheptide were
longer, more integrated and regular than those of control fish (Fig.1,2,3 and 4).
Fig.1 Section of villi of small Fig.2 Section of villi of small
intestineof fish fed with intestine of fish in the control
Nosiheptide
Fig.3 Section plane of villi of Fig.4 Section plane of villi of
small intestine of fish fed with small intestine of fish in the control
Nosiheptide
3. Discussion
It was reported that Flavomycin had good effect on promoting growth. The results in this
study showed that supplementation with 1.25mg/kg Nosiheptide could remarkably enhance daily
gain and reduce feed efficiency ratio of Jade Perch compared with Flavomycin.
It is known that villi are important for absorption function of small intestines. Thus the
development of villi is line with growth performance of animals. The results in this study showed
that the villi of small intestine of fish supplemented with 1.25mg/kg Nosiheptide were longer,
more integrated and regular than those of the control fish, indicating that Nosihetide was good for
development of intestinal villi of Jade Perch and enhanced the absorption of nutriments.
The results suggested that 1.25mg/kg Nosiheptide could protect intestinal villi of Jade Perch
in good order and promote assimilation of nutriment, therefore increase growth of Jade Perch.
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