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The timing of the preovulatory surge of LH and embryo production in superovulated cows
THERIOGENOLOGY
THE TIMING OF THE PHEDVULATOHYSUHGE OF LH AND EMBRYO PHCDWZTIQNINSUPEXOVUL4TEDC~S MiC!.Yadav', K.E. Ieslie2, and J.S. Walton' Deqrtment of Animal and Foultry Science Departmentof Clinical Studies Universityof Guelph Guelph, titario, CANAIlbNlG 2Wl Eighteen lactating Holstein-Friesiandairy cows were divided into three groups (A, B, and C) of six cows each. Group A was not superovulated, B and C were superovulated with either follicle stimulating hormone (FSHp, 4 mg im, twice daily for 5 days) or pregnant mares' serum gonadotrophin (PMSG, 2350 iu, single injection). Superovulatory treatment started on day 12 of the estrous cycle. Cloprostenol (500 ug) was administered 56 and 72 hours after commencement of treatments and at a correspondingtime of the cycle for cows in group A. All cows were inseminated three times using frozen semen at 12-hour intervals, starting 56 hours after the first injection of cloprostenol. Seven or 8 days after insemination, embryos were collected nor-surgically by flushing each uterine horn. All treated cows were then subjected to ovariectomy (per vagina) on the day after flushing, and the corpora lutea and any unovulated follicles were counted an-dmeasured. Blood samples were collected at intervals of 15 minutes from all cows via indwellingjugular cathetersfor a period of 9 hours on day -1, 0, 2, 8, and 10 around the start of superovulation(day 0). Blood was also sampled at 15-minute intervals continuouslyduring days 3-6. Plasma concentrations of luteinizing hormone (LH) were determined in these samples using a specificradioimmunoassayfor bovine LHdescribed by Bass, McNeilly, and Moreton (J. Heprod. Fert. 57:219222, 1979). The cows superovulatedwith FSHp had 8.3 2 1.5 ovulationsand the MSGtreated cows had 27.7 f_ 8.2 ovulations. Embryo recoveries were 36% and 29% for FSHp and PMSGtreatments, respectively. Cows treated with R&SG had an average of 8.5 unruptured folliclesgreater than 10 mm in diameter at ovariectomy,whereas FSHp-treatedcows had only 0.7. 'Ihe timing and duration of the preovulatorysurges of LH in these cows are illustrated in the table below. One cow treated with PMSGexhibited a surge of preovulatory proportions on day 6 after PMSG injection, in addition to the surge that occurred during estrus (day 3). Treatment
Time to onset of LH surge (h fran first injectionof cloprostenol? SE)
Durationof surge (h + SE)
A.
Control (n=4)
82.3 t
2.5
9.9 +
0.4
B.
FSHp (n=5)
49.7 It 3.5
11.0 +
1.5
C.
IMSG (n=5)
36.0 +
10.5 +
1.3
150
1.9
JANUARY
1983 VOL. 19 NO. 1
THE TIMING OF THE PHEDVULATOHYSUHGE OF LH AND EMBRYO PHCDWZTIQNINSUPEXOVUL4TEDC~S MiC!.Yadav', K.E. Ieslie2, and J.S. Walton' Deqrtment of Animal and Foultry Science Departmentof Clinical Studies Universityof Guelph Guelph, titario, CANAIlbNlG 2Wl Eighteen lactating Holstein-Friesiandairy cows were divided into three groups (A, B, and C) of six cows each. Group A was not superovulated, B and C were superovulated with either follicle stimulating hormone (FSHp, 4 mg im, twice daily for 5 days) or pregnant mares' serum gonadotrophin (PMSG, 2350 iu, single injection). Superovulatory treatment started on day 12 of the estrous cycle. Cloprostenol (500 ug) was administered 56 and 72 hours after commencement of treatments and at a correspondingtime of the cycle for cows in group A. All cows were inseminated three times using frozen semen at 12-hour intervals, starting 56 hours after the first injection of cloprostenol. Seven or 8 days after insemination, embryos were collected nor-surgically by flushing each uterine horn. All treated cows were then subjected to ovariectomy (per vagina) on the day after flushing, and the corpora lutea and any unovulated follicles were counted an-dmeasured. Blood samples were collected at intervals of 15 minutes from all cows via indwellingjugular cathetersfor a period of 9 hours on day -1, 0, 2, 8, and 10 around the start of superovulation(day 0). Blood was also sampled at 15-minute intervals continuouslyduring days 3-6. Plasma concentrations of luteinizing hormone (LH) were determined in these samples using a specificradioimmunoassayfor bovine LHdescribed by Bass, McNeilly, and Moreton (J. Heprod. Fert. 57:219222, 1979). The cows superovulatedwith FSHp had 8.3 2 1.5 ovulationsand the MSGtreated cows had 27.7 f_ 8.2 ovulations. Embryo recoveries were 36% and 29% for FSHp and PMSGtreatments, respectively. Cows treated with R&SG had an average of 8.5 unruptured folliclesgreater than 10 mm in diameter at ovariectomy,whereas FSHp-treatedcows had only 0.7. 'Ihe timing and duration of the preovulatorysurges of LH in these cows are illustrated in the table below. One cow treated with PMSGexhibited a surge of preovulatory proportions on day 6 after PMSG injection, in addition to the surge that occurred during estrus (day 3). Treatment
Time to onset of LH surge (h fran first injectionof cloprostenol? SE)
Durationof surge (h + SE)
A.
Control (n=4)
82.3 t
2.5
9.9 +
0.4
B.
FSHp (n=5)
49.7 It 3.5
11.0 +
1.5
C.
IMSG (n=5)
36.0 +
10.5 +
1.3
150
1.9
JANUARY
1983 VOL. 19 NO. 1