International Journal of Aquaculture, 2017, Vol.7, No.14, 94-100
97
Table 5 Sperm mass activity for test and control groups
Days of Storage
Duration of Storage (hrs)
Test group
Control group
1
24
+++
+++
2
48
++
+++
3
72
+
++
4
96
+
++
5
120
Nil
+
6
144
Nil
+
7
168
Nil
+
Mean
1.14±1.8
2.0±1.0
3 Discussions
Pre-storage results obtained in this research observed motility of 90% from milt extracted from both testes. This
value is in agreement with the suggested pre-extension motility of 80% and above (Akay et al., 1995; Urbanyi et
al., 1999; Adeyemo et al., 2007). The poor result obtained in the test group following storage can be attributed to
some factors one of which could be the repeated effect of freezing and thawing. Results obtained here revealed a
drastic drop in motility as well as viability from 70% at 24 hrs of storage to 50% at 48 hrs. All the cells were
found to be immotile at 120 hrs post storage and there were no viable cells as well. It is known that freezing
injuries can be caused by slower or faster than optimal cooling and thawing rates (Vivieros, 2002), hence the
sharp decline in motility and viability could be attributed to the accumulating injuries and exhaustion from
repeated freezing and thawing process. Another factor that could have caused the poor result is the lack of dilution
of the milt with the extender. This assumption is in line with the finding of Gwo et al. (2009) that undiluted
gametes are not suitable for freezing and they must be diluted with a suitable extender, which is a solution of
balanced salts and sometimes organic compounds.
Another major finding in this research is the performance of Na citrate. It is well known that Na citrate has the
ability to preserve milt of
Clarias gariepinus
when refrigerated (Mansour et al., 2005; Adeyemo et al., 2007), thus
it served as the control in this research. Results obtained showed that Na citrate at 4°C gave 20% motility and
viability by day 7 post storage. This finding supports the work of Mansour et al. (2005) who observed that at
optimal condition when buffered saline solution is used for storage of milt of
Clarias gariepinus
at 4°C, sperm
viability persists for > 7 days. Lardy and Philips (1940) and Foote (1980) also reported that physiological buffers
have the ability to dilute semen and maintain its viability for some days when refrigerated. It is also noteworthy to
state that the result with this experiment confirms the viability of the milt used in this research.
4 Materials and Methods
4.1 Experimental fish
Two male brood stocks of
Clarias gariepinus
14months of age, weighing 1.5 kg each, were purchased from a
reputable farm (Olompet Holdings) in Abuja for the experiment. The male brood stocks were conveyed to the
Theriogenology Laboratory of the Faculty of Veterinary Medicine University of Abuja, in well aerated containers.
The choice of males was based on the possession of well vascularized genital papilla (Figure 2).
4.2 Experimental design
The experimental method adopted in any research study to a large extent is dependent on the nature and objective
of the study. There were two groups comprising the test and the control groups. The Test group was the left testis
dipped in Na citrate placed in a properly labeled container and preserved at -20°C. The control group included
milt extended in Na citrate shared into seven insulin syringes, properly labeled and stored at 4°C, a condition
already known to preserve semen of the African catfish. This group served as the control for the experiment. The
two groups were observed for a period of seven days and percentage motility, life/dead ratio as well as mass
activity of spermatozoa in these samples were recorded. The control group involved taking out a sample out of the
seven syringes each day, while test group involved daily thawing of the sperm sac sample to collect and examine
milt.
