Potentials of short term and long term cryopreserved sperm of the African giant catfish (Clarias gariepinus Burchell, 1822) for aquaculture

To service the growing demand for male African giant catfish (Clarias gariepinus) broodstock for aquaculture in Nigeria, and to conserve valuable genetic resources, we improved both short-term (in deep freezer at -35°C) and long-term cryopreservation (in liquid nitrogen at -296°C) of catfish sperm. Catfish sperm cryopreserved at -35°C using three different types of cryodiluents composed of 10% methanol, glycerol or dimethylsulphoxide (DMSO) with 15% non-permeating cryoprotectant (skim milk) and 75%  phosphate-buffered saline (PBS) as extender was evaluated at day 1 to 28. Sperm motilities on thawing for the two cryodiluents that contained glycerol and DMSO were the same (p > 0.05) while those for the cryodiluent that contained methanol were significantly lower (p < 0.05). Sperm cryopreserved in DMSO and glycerol provided hatching at least 50% of catfish eggs. Liquid nitrogen (LN2) was with the same 3 cryoprotectants and one new extender based on glucose and skim milk (Ginzburg fish Ringer, GFR). Two thawing procedures were tried: 1) In the first trial, one set of sperm was frozen with different  cryodiluents with extenders in the freezer at -10°C and 2) Stored for up to 8 months in LN2. Sperm with up to eight months cryopreservation from the first trial when thawed at room temperature at 27°C for 15 min gave 0 - 6.25% fertilization rate (FR). The sperm stored for two months in the second trial when rapidly thawed at 35°C for 5 min gave better results. The FR of 94% was achieved with a cryodiluent of DMSO with 5% glucose solution and PBS when the cryopreserved sperm was thawed at 35°C. Also, DMSO in combination with PBS resulted in a higher FR than either glycerol or methanol. However, sperm cryopreserved with glycerol had the lowest motility rate in the 2 trials (p < 0.05). The use of  cryopreserved sperm did not significantly affect (p < 0.05) the survivability of the fry. The use of cryopreserved sperm of the African catfish for fry production will be especially beneficial in Nigeria where reliable sperm supply is a major bottleneck in the catfish aquaculture industry.Key words: Cryopreservation, sperm motility, Clarias gariepinus, African giant catfish

Genetic characterization of Nigerian indigenous pig using polyacrilamide gel electrophoresis

The genetic structure of Nigerian indigenous pigs (NIP) and crossbred pigs were investigated using polyacrylamide gel electrophoresis. A total of 79 NIP blood samples were collected from three different locations within South-western Nigeria namely, Igbara Odo, Ekiti State (33 samples), Ogbooro, Oyo State (30 samples), and Institute of Agricultural Research and Training (IAR&T), Oyo State (16 samples). In addition, 41 crossbred pig blood samples were collected from the Teaching and Research Farm (T&R Farm), Obafemi Awolowo University, Ile-Ife. The blood serum samples obtained from the pigs were subjected to Sodium dodecyl sulphate (12%) SDS-PAGE gel electrophoresis. A total of 19 protein loci were scored for the NIP and 16 for crossbred samples. The SDS-PAGE electrophoretic profiles were analysed using PAST package (2005) to determine genetic similarity coefficients and construct phylogenetic dendrograms using Nei’s standard genetic distance. Ogbooro NIP samples showed a very high level of genetic similarity (91%) while IAR&T was 87% whereas Igbara Odo was 56%. The T&R Farm crossbred pigs showed 81%. The total local pig samples from the three locations gave a high genetic similarity coefficient of 84% confirming their genetic relatedness. The high genetic similarity observed in the indigenous pig samples in Ogbooro indicated a level of inbreeding of pig stocks in this locality which can be conserved as a genetic resource for breeding programmes for pure NIP in the future.Key words: Animal genetic resources, conservation, Nigeria indigenous pig, electrophoresi