Maintenance of pregnancy in goats: Relationships between the fetus, the corpora lutea and the concentrations of progesterone in the maternal plasma
Jarrell, Vickie Louise
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https://hdl.handle.net/2142/23248
Description
Title
Maintenance of pregnancy in goats: Relationships between the fetus, the corpora lutea and the concentrations of progesterone in the maternal plasma
Author(s)
Jarrell, Vickie Louise
Issue Date
1989
Department of Study
Animal Sciences
Discipline
Animal Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Animal Culture and Nutrition
Language
eng
Abstract
Reproductive efficiency in goats is limited by spontaneous pseudopregnancy and abortion. These conditions are affected by the need for the corpus luteum (CL) to maintain progesterone throughout gestation. A study was done to understand the interrelationships of the CL, maintenance of pregnancy, the presence of the fetus and concentrations of progesterone. The influence of the number of CL on the concentration of progesterone and maintenance of pregnancy was assessed first by monitoring concentration of progesterone in 79 goats from day 0 to day 45 of gestation. The qualitative and quantitative relationships of the numbers of CL and fetuses, the concentration of progesterone and the maintenance of pregnancy was then assessed by systematic alteration of numbers of CL and fetuses at laparotomy near day 45 of gestation. Adjustment of numbers of CL was by unilateral ovariectomy and fetus numbers were adjusted by fetectomy. The concentration of progesterone was measured by radioimmunoassay of plasma samples collected frequently from the jugular vein from day 0 to day 75.
Concentration of progesterone in the plasma of all animals was less than 1.0 nanogram/milliliter (ng/ml) until day 3 after first mating then increased to a maximum concentration at 8.5 ng/ml. Concentration of progesterone declined to 5.0 ng/ml by day 35 irrespective of numbers of CL although concentration of progesterone had been positively related to the number of CL from day 7 to day 25.
Removal of an ovary with no CL did not reduce progesterone but removal of an ovary with CL decreased concentration of progesterone for 3 days. Concentration of progesterone rebounded in 3 days to that before unilateral ovariectomy indicating that there was a compensating mechanism functioning at day 45. Although removal of a greater proportion of the total number of CL resulted in a greater decrease in progesterone, there was no relationship between number of CL and concentration of progesterone from day 45 to day 75.
Concentration of progesterone was not affected by number of fetuses provided 1 live fetus was present. Removal or death of all fetuses resulted in pseudopregnancy. Pseudopregnancy was characterized by persistent CL in the absence of a fetus and decreased progesterone from day 45 to day 75. The goat fetal-placental unit was found to be luteotrophic between day 45 and 75 based on greater concentrations of progesterone in pregnant compared to pseudopregnant goats.
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