Effects of serum on in vitro maturation of Korean native cattle oocytes

Influence of different levels of steer serum on production of fertilisable buffalo oocytes in vitro

“…The only previous study on the use of steer serum supplementation in the culture of buffalo oocytes (Chauhan and others 1998) used steer serum at an inclusion level of 10 per cent without any exogenous gonadotrophin and cumulus expansion was observed in 35 per cent of oocytes which is similar to the value observed at this level of steer serum inclusion in the present study. However, the maturation rate obtained when TCM‐199 was supplemented with steer serum was not as high as that reported in sheep by Reddy and Shankarappa (1999) who observed 74 per cent maturation rate at 10 per cent level; in cattle, by Monaghan and others (1993) who observed 81 per cent maturation rate at 20 per cent level of steer serum, Nakagawa and others (1994) who observed an 83 per cent maturation rate at 10 per cent level of steer serum and Choi and others (1997) who observed 93·8 per cent, 90·9 per cent and 80·6 per cent maturation rate at the 5 per cent, 10 per cent and 20 per cent levels of steer serum, respectively. This may be due to different methodologies of oocyte maturation assessment adopted by various workers but could also reflect variations in the levels of endogenous gonadotrophins and steroid hormones in steer serum.…”