International Journal of Aquaculture, 2015, Vol.5, No.29 1
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5
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determine the sperm quality of broodstocks expressed
in term of sperm count and sperm motility.
Materials and Methods
Broodstock Maintenance
Fifteen male broodstock of
Clarias
gariepinus
weighing
between 400 g-700 g were obtained from a fish farm in
Makurdi, Nigeria. They were transported to the fish
hatchery of the University of Agriculture Makurdi and
maintained in concrete tanks for a period of two weeks
during which they were acclimatized. During this
period of acclimatization, they were fed to satiation
using 4 mm commercial feed.
Collection of Milt
Each male broodstock of
C. gariepinus
were weighed
and sacrificed by spinal transection, and the testes
removed. Blood and other tissue were rinsed away using
saline solution. The testes were weighed and expressed
as percentage body weight of the fish. Incision was
made into the lobes of the testes, and the milt was
squeezed into a petri dish, and its volume was measured
with plastic syringe.
Determination of sperm count
Concentration of sperm was determined by counting the
number of spermatozoa in simple diluents with KCl in
a ratio of 1:50 under 400 x magnifications using Neubauer
improved counting chamber (Rainis et al., 2003).
Determination of Percentage Motility
Percentage Motility for each sample was estimated
using a light microscope at 400 x magnification
immediately after addition of a drop of semen with 50
drops of KCl in a non-activating medium. Immotile
sperm cells (ISC) were counted and the motile sperm
cells were also quickly counted until there was no more
sign of motility. Whole sperm cell (WSC) was counted
using method described by Canyurt and Akhan
(2008).
The motile sperm cells (MC) were calculated thus
Determination of Level of Correlation of parameters
and Regression
The pearson’s correlation matrix between the different
parameters was done using Graphpad Prism 5 while
regression analysis was done using Minitab 14 and
Microsoft Excel 2007.
Results
Sperm quality
Table 1 shows the sperm quality parameters of the
broodstocks of
Clarias gariepinus
. The milt volume of
the experimental fish ranged from 0.2 ml to 1.3 ml.
The highest milt volume (1.3 ml) was obtained from
the broodstock with 639.8 g body weight and testes
weight of 3.88 g, and the least milt volume (0.2 ml)
was obtained from the broodstock fish with 496.6 g
body weight and 0.97 g testes weight.
The highest Gonado-somatic index GSI (0.606%) was
obtained from broodstock with body weight of 639.8 g
and 3.88 testes weight while the least GSI (0.193%)
was from 465.5 g body weight and 0.9 g testes weight.
Percentage motility of the experimental semen varied
between 57.1% and 93.7%. The sperm count in the
experimental fish varied between 38 x 10
9
spm/ml to
97 x 10
9
spm/ml.
Table 2, shows the correlation matrix for % motility,
sperm count, volume of semen, weight of male, and
weight of testes. Correlation between % motility and
sperm count was significant (P = 0.00007 and r = 0.845)
which indicates a strong positive correlation between
the two parameters. Correlation between weight of testes
and volume of semen was also very significant (P =
0.0000 and r = 0.978. Correlation between body weight
and weight of testes was significant (P = 0.0049 and r
= 0.684) and strongly positive. Another significant
correlation was the correlation between volume of semen
and the weight of broodstock which was also a strong
positive correlation (P = 0.0053 and r = 0.679).
Equations 1 and 2 shows the multiple regressions to
predict volume of semen from weight of male and
weight of testes and to predict % motility of sperm
from Volume of semen, sperm count and weight of
testes respectively. Regression equation 1 is significant (P
= 0.000) and the co-efficient of determination (95.7%
adjusted as 94.9%) shows that 94.9% of variance in
volume of semen is as a result of variance in the
predictors which include weight of male and weight of
testes. On the other hand, regression equation 2 is
significant (0.000) with the co-efficient of determination
(79.2% adjusted as 73.5%) showing that 73.5% of
variance in % sperm motility being accounted for by
variance in the predictor variables of the equation.
