Masters Theses

Date of Award

6-1977

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

Frank Masincupp

Committee Members

John Hitchcock, R. L. Murphree, E. R. Lidvall

Abstract

During the summer of 1976 and the winter of 1976-77, seventy-five prepuberal gilts were used to determine the effects of various hormone treatments on their age at puberty. In Trial I, 45 prepuberal gilts were injected at either 90 or 120 days of age with 50 mg progesterone followed in 24 hours by 1 mg estradiol benzoate. The controls were injected with saline. The gilts were slaughtered 84 days later. In Trial II, nine of the above gilts were injected at 165 to 185 days of age with .4 mg estradiol benzoate twice each day for three consecutive days. The gilts were slaughtered on the fifth day following injection (day one is first injection day). In Trial III, 30 gilts were injected at 150 days of age with: .4 mg estradiol benzoate each day for three consecutive days. Ten of the gilts received 500 lU of human chorionic gonadotrophin (HCG) 36 hours after the last estrogen injection. Results of these experiments show that .4 mg estradiol benzoate (EB) each day for three consecutive days was effective in inducing estrus. However, in some cases the induced estrous cycles were of longer than normal duration. The gilts were bred (five natural and five artificially) on their second estrous cycle and on each subsequent cycle until slaughter. The EB/HCG treatment also induced estrus. The gilts were artificially bred (AI) on the induced cycle. None of the gilts settled on this breeding, but all the gilts re-cycled within 23 days, were bred again and all settled. The control gilts were limit-fed the standard 16 percent UT ration from 200 pounds and flushed as they approached 200 days of age. The control gilts were bred (five natural, five artificially) on their second estrus. The EB, EB/HCG, and control gilts had post-treatment cycles of 40.1, 22.3, and 21.2 days respectively. There was no difference in the number of live feti found at slaughter.

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