Superovulation in Rubia Gallega cows with a single subcutaneous injection of FSH

Abstract

The effect of oxytocin in addition to an prostaglandin (PGF2a) injection, given on day 12 of the oestrous cycle (at the time of fifth and sixth FSH injection) in goats pretreated with human chorionic gonadotrophin (hCG) on day 7 of the oestrous cycle was studied. Sixteen cyclic local nondescript goats were randomly allocated to control (without oxytocin, n=8) and treatment (oxytocin, n=8) superovulation groups. All goats in the control group received a total of 20 NIH FSH S1 units divided into eight doses (4/4, 3/3, 2/2 and 1/1 units) over 4 days (day 10 to 13 of the cycle) and 10 mg dinoprost tromethamine (PGF2a) on day 12. Goats in the treatment group in addition also received 500 IU hCG on day 7 of the oestrous cycle and 50 IU oxytocin intramuscularly with the fifth and sixth FSH injection on day 3 of the superovulatory treatment. Goats in both the groups were administered 500 IU hCG, 10–16 h after the onset of oestrus and naturally serviced at 12 hourly intervals till the end of the oestrus. Laparotomies were performed on all goats on day 6 for assessment of ovarian response and embryo recovery. Blood samples were taken on day 7, (before hCG or any pretreatment), day 10 (before beginning of FSH administration), day 12 (before PGF2a administration), day 0 (day of superovulatory oestrus) and day 6 (day of flushing) for the estimation of the progesterone. There was a significant decrease in the number of corpora lutea/donor in the treatment group compared to the control group (0.8±0.3 vs 5.1±0.9; P<0.01). The number of white avascular corpora lutea were significantly more in treatment group than in control group (5.6±2.2 vs 1.5±1.5; P<0.05). Similarly, the number of unovulated large follicles were also more in the treatment group (5.5±1.2 vs 2.0±0.9). The total number of embryos recovered, significantly decreased in treatment group compared to the control group (0.7±0.3 vs 2.8±0.5; P<0.05). Plasma progesterone levels on the day of oestrus in treatment and control group was almost similar (0.6±0.1 vs 0.6±0.1 ng/ml). Plasma progesterone levels on other corresponding days in both groups did not vary significantly. The injection of oxytocin in addition to PGF2a in goats pretreated with hCG could not increase ovarian response in terms of the number of normal functional corpora lutea and number of embryos recovered.