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Superovulation in the prepuberal calf
THERIOGENOLOGY
SUPEROVULATION IN THE PREPUBERAL CALF D. Jillella and A.A. Baker Dept.'of Animal Production, University of Queensland, St Lucia, Qld 4067 The induction of superovulation in the prepuberal calf has been achieved by several workers (Foote and Onuma, J. Dairy Sci., 53:1681-1692, 1970). Mainly either HCG or exogenous LH has been used to induce ovulations of PMSG primed follicles. There is very little information on the effect of GnRH on endogenous LH release and ovulations in prepuberal calves primed with PMSG (Mellin et al., Theriogenology 4:41-58, 1975). The following experiment was carried out to evaluate the effect of GnRH and HCG on serum LH levels and ovulations in prepuberal calves primed with either progesterone, PMSG and oestrogen or PMSG and oestrogen. Nine prepuberal Santa Gertrudis x dairy calves were assigned at random to three groups. The day on which one of the groups first received a hormonal treatment was counted Day i. All hormonal treatments were given by intramuscular injection. On Days i, 2, 3 and 4 Group I calves were given 25 mg progesterone (Progestin, Intervet, Cambs., U.K.). On Day 5 all 9 calves were given 2,000 i.u. PMSG (Folligon, Intervet, Cambs., U.K.). In addition to PMSG Group I calves received 25 mg progesterone. On Days 6 and 7 Group I calves were given 12.5 mg progesterone. On Day 8 all 9 calves were given i0 mg oestrogen (Stilboestrol, May & Baker, Australia). On Day 9 Group I and II calves were given 0.5 mg GnR}I (Abbott Lab., Illinois, U.S.A.) and Group III calves received 3~000 i.u. HCG (Chorulon, Intervet, Cambs., U.K.) at 0900 hours. Blood was collected from all calves one hour before and at two hourly intervals on four occasions after either GnRH or HCG injection, and the serum later assayed for LH by radioimmunoassay. Calves were slaughtered 6 days after either GnRH or HCG injection, the reproductive tracts collected and the ovarian response ascertained. Results of ovarian response and LH levels are presented in Table I. GnRH appears to be a potent LH releasing substance in the prepuberal female calf. However, the maximum level of LH recorded in each calf after either GnRH or HCG administration does not appear to be related to the calf's ovulation rate. With the treatment regimens used here HCG induced more ovulations in PMSG primed calves than did GnRH. TABLE I.
Group
I
II
III
120
Ovarian response and LH levels in treated calves. Calf No. 158 160 163 159 161 165 162 164 166
Serum LH levels (ng/ml) on Day 9 0800 1100 1300 1500 1700 Hrs. Hrs. Hrs. Hrs. Hrs. 8.5 34.3 25.8 ii.i 10.3 9.0 9.5 7.0 6.7 5.1 7.6 27.8 9.4 7.6 7.5 7.1 15.2 8.1 6.7 6.4 7.0 15.3 8.7 7.3 8.4 10.6 15.1 10.5 9.7 10.8 8.5 8.8 7.3 7.5 6.7 8.3 33.5 10.6 9.4 9.4 12.3 11.5 12.7 11.4 12.3
Ovarian Response Unovulated Ovulations follicles 13 9 28 0 >i00 0 36 3 >i00 0 12 2 5 5 15 25 19 16
JANUARY 1981 VOL. 15 NO. 1
SUPEROVULATION IN THE PREPUBERAL CALF D. Jillella and A.A. Baker Dept.'of Animal Production, University of Queensland, St Lucia, Qld 4067 The induction of superovulation in the prepuberal calf has been achieved by several workers (Foote and Onuma, J. Dairy Sci., 53:1681-1692, 1970). Mainly either HCG or exogenous LH has been used to induce ovulations of PMSG primed follicles. There is very little information on the effect of GnRH on endogenous LH release and ovulations in prepuberal calves primed with PMSG (Mellin et al., Theriogenology 4:41-58, 1975). The following experiment was carried out to evaluate the effect of GnRH and HCG on serum LH levels and ovulations in prepuberal calves primed with either progesterone, PMSG and oestrogen or PMSG and oestrogen. Nine prepuberal Santa Gertrudis x dairy calves were assigned at random to three groups. The day on which one of the groups first received a hormonal treatment was counted Day i. All hormonal treatments were given by intramuscular injection. On Days i, 2, 3 and 4 Group I calves were given 25 mg progesterone (Progestin, Intervet, Cambs., U.K.). On Day 5 all 9 calves were given 2,000 i.u. PMSG (Folligon, Intervet, Cambs., U.K.). In addition to PMSG Group I calves received 25 mg progesterone. On Days 6 and 7 Group I calves were given 12.5 mg progesterone. On Day 8 all 9 calves were given i0 mg oestrogen (Stilboestrol, May & Baker, Australia). On Day 9 Group I and II calves were given 0.5 mg GnR}I (Abbott Lab., Illinois, U.S.A.) and Group III calves received 3~000 i.u. HCG (Chorulon, Intervet, Cambs., U.K.) at 0900 hours. Blood was collected from all calves one hour before and at two hourly intervals on four occasions after either GnRH or HCG injection, and the serum later assayed for LH by radioimmunoassay. Calves were slaughtered 6 days after either GnRH or HCG injection, the reproductive tracts collected and the ovarian response ascertained. Results of ovarian response and LH levels are presented in Table I. GnRH appears to be a potent LH releasing substance in the prepuberal female calf. However, the maximum level of LH recorded in each calf after either GnRH or HCG administration does not appear to be related to the calf's ovulation rate. With the treatment regimens used here HCG induced more ovulations in PMSG primed calves than did GnRH. TABLE I.
Group
I
II
III
120
Ovarian response and LH levels in treated calves. Calf No. 158 160 163 159 161 165 162 164 166
Serum LH levels (ng/ml) on Day 9 0800 1100 1300 1500 1700 Hrs. Hrs. Hrs. Hrs. Hrs. 8.5 34.3 25.8 ii.i 10.3 9.0 9.5 7.0 6.7 5.1 7.6 27.8 9.4 7.6 7.5 7.1 15.2 8.1 6.7 6.4 7.0 15.3 8.7 7.3 8.4 10.6 15.1 10.5 9.7 10.8 8.5 8.8 7.3 7.5 6.7 8.3 33.5 10.6 9.4 9.4 12.3 11.5 12.7 11.4 12.3
Ovarian Response Unovulated Ovulations follicles 13 9 28 0 >i00 0 36 3 >i00 0 12 2 5 5 15 25 19 16
JANUARY 1981 VOL. 15 NO. 1