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Title: The effect of the Booroola fecundity gene on the control of ovarian function in sheep
Author: Boulton, Margaret Iona
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1994
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Ewes possessing the single, or major, Booroola fecundity (FecB) gene have higher ovulation rates than non-carriers of the FecB gene. Previous investigations into the hormonal control of ovulation rate in ewes possessing the FecB gene have been complicated by comparisons of animals of different strains, or by using animals which were of unknown genetic background. The establishment of breeding lines has enabled animals to be chosen whose pedigree is well documented and whose genetic relationship to other members within the same experimental group can be carefully regulated. The work in this thesis has investigated gene specific differences in FSH, inhibin, oestradiol and IGF-1 as possible agents in promoting prolificacy in two populations (F2 and backcross) of Booroola Scottish Blackface ewes which differ only in the major Booroola fecundity gene and closely related genes. In both populations, 80% of ewes were induced to ovulate during seasonal anoestrus in response to a single i.m. injection of hCG (750 i.u.) confirming that the mechanisms controlling ovulation rate are still present in the non-breeding season. During the breeding season and seasonal anoestrus, FecBFecB ewes had higher ovulation rates and higher peripheral FSH concentrations compared to Fec+Fec+ ewes from the F2 population. However, FSH concentrations did not differ between FecBFec+ and Fec+Fec+ ewes from either F2 or backcross populations, despite significant differences in breeding season ovulation rate. In ovariectomised ewes, FSH concentrations were similar between FecBFec+ and Fec+Fec+ ewes from both populations, but significantly higher in FecBFecB ewes, supporting the theory of genotypic differences in pituitary gland release. Since genotypic differences in FSH concentration were not always associated with genotypic differences in ovulation rate, the hypothesis that there was a difference in follicular responsiveness to FSH, in terms of growth and/or oestradiol production, was tested by the use of an in vitro culture system.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available