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ThesisItem Open Access COMPARATIVE STUDY ON THE CRYOTOLERANCE OF IN VITRO MATURED AND VITRIFIED BOVINE OOCYTES SUPPLEMENTED WITH L- CARNITINE AND NIACIN(COLLEGE OF VETERINARY AND ANIMAL SCIENCES MANNUTHY, THRISSUR, KERALA VETERINARY AND ANIMAL SCIENCES UNIVERSITY, 2023-03-23) ANJITHA K; Dr. Amritha AravindThe study was designed to assess the cryotolerance of in vitro matured bovine oocytes, supplemented with L- carnitine and niacin in maturation media,and vitrified using cryoloop technique. Bovine ovaries were collected from the slaughterhouse and cumulus-oocyte complexes (COCs) were retrieved by follicular aspiration. The yield of grade A, B, C and D oocytes was 21.82 ± 0.02, 36.21 ± 0.03, 25.14 ± 0.02 and 16.81 ± 0.02, respectively. Culture quality COCs (Grade A and B) were selected and randomly allocated to three different experimental groups. Group I oocytes (control), were subjected to in vitro maturation (IVM) in basic maturation media, while Group II and III oocytes (experimental groups) were matured in media supplemented with L- carnitine (0.6 mg/mL) and niacin (400 µM/mL), respectively. The mean per cent of oocytes with cumulus cell expansion noticed in different groups were 80.92 ± 0.02, 79.18 ± 0.03 and 87.95 ±0.02 for Group I, II and III, respectively. A significantly high (p ˂ 0.05) cumulus cell expansion rate could be observed in niacin treated group than L- carnitine, whereas a difference close to being statistically significant (p = 0.057) was noticed between niacin and control. The mean per cent of IVM rates observed were 87.02 ± 0.02, 85.12 ± 0.04 and 94.73 ± 0.02, respectively in Groups I, II and III. A significantly high (p ˂ 0.05) maturation rate could be observed in niacin treated group than Lcarnitine, whereas no significant difference was noticed between control and experimental groups. The matured oocytes were subjected to cryoloop vitrificationusing dimethylsulfoxide (15%), ethylene glycol (15%) and sucrose (0.05M) as cryoprotectants. The mean per cent of survival rates observed in the study was 67.26 ± 0.05, 76.34 ± 0.05 and 79.68 ± 0.03 for Group I, II and III,respectively. A higher survival survival rate with a trend towards significance (p = 0.069) could be observed in vitrified oocytes supplemented with niacin than control. However, no significant difference could be observed between L- carnitine and niacin supplemented oocytes and L- carnitine and control. Shrinkage of cytoplasm was the most common type of cryodamage observed in all the three groups followed by cracked zona pellucida, abnormal shape and increased peri vitelline space. The survived oocytes were subjected to in vitro fertilization with no significant difference between the groups. The present study revealed the beneficiary effect of supplementing niacin over L- carnitine in maturation media as it increased the maturation rate of bovine oocytes with higher survival rates.
