Dose effect of Follicle Stimulating Hormone for superovulation of crossbred Targhee ewes

THERIOGENOLOGY DOSE EFFECT OF FOLLICLE STIMULATING HORMONE FOR SUPEROVULATION OF CROSSBRED TARGHEE EWES. C.L. Smith, Department of Large Animal Clinical Sciences, Michigan State University, East Lansing, Michigan 48824. Follicle Stimulating Hormone (FSH), combined with Prostaglandin F2a (PGF2a) was evaluated for its abirityto cause superovulation in crossbred Targhee ewes. The effect of varying FSH dosage was tested by giving 12 mg, 14.5 mg, 17 mg, 19.5 mg, 22 mg and 30 mg; and evaluating ovarian response. A possible effect of the timing of FSH treatment within the cycle of these ewes was tested by initiating treatment on day 7, 8, 9 and 10 of the estrous cycle of ewes and evaluating ovarian response. Eighty crossbred ewes were given FSH, twice a day for 3.5 days; 20 mg Prostaglandin F2a were given oh the third day to induce estrus in synchrony with the FSH treatment. To evaluate ovarian response the structures on the ovaries of these ewes were identified, counted and diameter measured via a midline laporatomy. In addition, embryos were flushed from the uteri, identified and evaluated for fertilization and degeneration. A significant effect of FSH dose was seen on Corpora Lutea (CL) numbers. A dose response curve for effect of FSH dose on CL numbers was constructed from a computer regression analysis. A significant (Pc.05) cubic relationship between FSH dose and CL numbers was seen. A dose response curve for effect of FSH dose on embryo numbers was also constructed from a computer regression analysis. A significant (Pi.05) linear relationship between FSH dose and embryo numbers was seen. The dose of FSH had no effect on other ovarian structures, or fertility or degeneration of embryos. The time of FSH initiation within the cycle had no effect on any of the variables. An optimum dose of 19.5 mg to 26 mg FSH was estimated from these analyses. The data from the FSH treatments is summarized in the following table. FSH m.9 Dose -0 12 14.5 17 19.5 22 30

No. of Ewes 7 3 1; 18 18 15

* Mean CL 1.86 6.67 6.67 8.40 12.06 14.39 10.73

* Mean Embryos 1.14 1.33 4.33 5.87 7.72 8.44 7.93

Total CL

:: 20 126 217 259 161

Total Total Total UnfertilizedDegenerated Embryos Ova Embryos

48 13 88 139 152 119

0 3 1 10 15 17 1

:

13 9

* Adjusted mean

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JANUARY

1984 VOL. 21 NO. 1