INFLUENCE OF EXTENDERS ON THE DIFFERENT AGE GROUP OF COMMON CARP BROODERS IN TERMS OF SPERMATOLOGICAL AND FERTILIZATION PARAMETERS
Age is considered as an important factor affecting the quality of milt in fishes. There have been considerable variations in the spermatological qualities of milt collected from a single individual at different occasions in the same or in different seasons of a year. Extenders having osmolality similar to that of seminal fluid was found to be successful in the cryopreservation of fresh milt. There are many extenders available based on the ionic composition of seminal plasma of species. Extender that has to be used for cryopreservation varies between species and spotting a universal extender is far from reality. Therefore it is felt necessary to identify suitable extender based on the available reports for Cyprinus carpio. Hence the present study was undertaken to know the best age group of brooder and extenders for milt cryopreservation and the effect of extenders on the different age group of brooders of C. carpio.
Earthen pond of size 0.1 hectare (50 m × 20 m) was used for the broodstock development. The pond was stocked with C. carpio fingerlings of 40 days (8.91±3.64 g) old procured from Manimuthar National Fish Seed Farm. They were fed with farm mixed wet feed balls of ground nut oil cake and rice bran at 1:1 ratio. The fishes were grown for a period of one and a half years. Milt was collected by gentle stripping from the brooders at 6th month, 12th month and 18th month in graduated cryovials of 2.5 ml volume. Spermatological parameters such as motility duration, motility score, live and dead cells, calcium and magnesium levels (Fig.1) were studied. Then the milt was diluted with Freshwater Fish Saline and Modified Fish Ringer at a dilution rate of 1:40. The diluted milt was analysed for its spermatological quality and fertilization capacity.
The results (Table 1) showed that the highest mean motility duration (72.3±3), fertilization rate (91.3±1.5) and hatching rate (76.6±3) was observed in milt collected from 12 months old brooder diluted with Freshwater Fish Saline when compared with other age group and extenders. Hence the present study suggested the use of brooders at 12 months old and Freshwater Fish Saline as extender for cryopreservation.
