Correlation between Serum Steroid Hormone Profiles Before, during and after Norgestomet Induced Oestrus and Occurence of Conception in Repeat Breeder Crossbred Cows*

A total of 16 crossbred repeat breeder cows were treated with norgestomet (Syncromate-B) ear implants for nine days. At the time of implant insertion, two ml of SMB injection was adminisetred to all the cows intramuscularly on day 10 of the oestrous cycle to induce oestrus. AI was done at 48 and 72 h after implant removal. Pregnancy diagnosis was done at 60 days following AI after induced oestrus to assess the first service conception rate and it was found to be 43.75 per cent. Blood samples were collected from all the cows at different stages following norgestomet treatment for oestradiol and progesterone assays. The mean progesterone level (ng/ml) and oestrogen levels (pg/ml) at the time of natural oestrus, day of initiation of oestrus induction treatment, implant removal and at first AI and at second, fourth and sixth day following first AI in cows which became pregnant (n=7) was 0.36±0.08, 7.19±0.46, 1.45±0.24,0.18±0.05, 1.05±0.20, 1.70±0.22 and 3.37±0.77 and 38.83±12.24, 11.33±3.54, 43.65±17.05, 20.63±3.44, 10.37±6.07, 9.68±3.71 and 14.28±4.77 respectively and the corresponding values in cows which did not conceive (n=9) at induced oestrus were 0.51±0.09, 5.24±0.43, 1.29±0.20, 0.23±0.03, 0.57±0.15, 0.99±0.27 and 1.62±0.26 and 15.13±5.14, 19.57±5.50, 25.86±13.54, 19.11±4.36, 23.51±5.35, 24.39±6.60 and 20.40±6.41, * Part of Ph.D thesis submitted by the first author to the Tamil Nadu Veterinary & Animal Sciences University, Chennai-51 1. Associate Professor & Head, Dept. of ARGO, VC & RI, Namakkal 2. Professor and Head 3. Director of Extension Education, TANUVAS 4. Professor 5. Dean, VC & RI, Namakkal respectively. It is concluded that serum progesterone and oestrogen levels at various stages following syncromate –B therapy influenced the conception rate in repeat breeder cows.