Date of this Version
Thesis (M.S.)—University of Nebraska—Lincoln, 1973. Department of Animal Science.
Controlling the estrous cycle in the female has been proclaimed for years as an important tool in the management of livestock breeding programs. The most popular method used in regulating the estrous cycle involves the administration of progestogens for varying periods of time. After treatment in cattle, estrus and ovulation generally occur over a short period of time (2 to 3 days).
Numerous studies have been conducted using progestogens alone or in combination with other hormones to control the estrous cycle. The usage of these hormone(s) in synchronizing estrus and ovulation has been quite successful. Conception at first post-treatment estrus, however, tends to be impaired. Recent work with a progestogen ear implant has shown promising results in synchronizing estrus and ovulation and in improving fertility.
This thesis contains a review of literature concerning experimentation with hormonal materials for estrous cycle synchronization, possible mechanisms by which progestogens control the cycle and cervical mucus cyclic changes. Results are presented from four experiments dealing with methods and action of a progestogen
17-alpha-19-acetoxy-11-beta-methyl-19-norpreg-4-ene-3,20-dione (SC21009) used in cattle and rats. Synchronization effect, conception rate, serum LH levels and cervical mucus amino acid contents were reported in cattle treated with the progestogen ear implant. Actions of the progestogen in the rat were determined by the estrous cycle activity, autopsy data and hormone levels of LH and TSH in the pituitary and blood serum.
Advisor: E. F. Ellington