Doctoral Dissertations

Date of Award

12-1972

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

Don O. Richardson

Committee Members

J. T. Miles, Robert R. Shrode, R. L. Murphree, William James Davis

Abstract

The first objective of this study was to evaluate a radioimmunoassay technique for the assay of estrogen. Secondly, the interrelated changes in the concentrations of progesterone and estrogen were to be determined in peripheral plasma of non-bred, non-pregnant and pregnant Holstein cows. Progesterone was determined by competitive protein-binding. Six hundred twenty-nine blood samples were collected from the jugular vein of 14 lactating cows. Sample collection began five days prior to estrus and continued at daily intervals for 25 days post-insemination. Non-bred cows were bled through one or two cycles. The cows were divided into the following groups: A) non-bred (estrus detected), B) non-bred (estrus undetected), C) non-pregnant and D) pregnant. In Groups A, C and D, Day 0 represents the day of estrus. In Group B, Day 0 represents the day of highest estrogen concentration. The extraction efficiencies for labeled and unlabeled proges-terone were 93.58 ± 0.78 percent (mean ± standard error) and 90.20 ± 2.15 percent, respectively. The extraction efficiencies for 20 pg and 50 pg of estradiol-17β were 91.18 ± 4.58 percent and 88.57 ± 5.24 percent, respectively. The extraction efficiency for 4 nanocuries of estradiol-17β-2, 4, 6, 7-h3 was 94.04 ± 0.59 percent. The unlabeled and labeled extraction effi-ciencies were not significantly different (P> 0.10). The estradiol-17β antibody exhibited considerable crossreaction with estrone, while the crossreaction with estriol was negligible. The coefficients of variation for points on progesterone and estrogen standard curves were less than 10 percent, with the exception of ICQ pg of estradiol-17β (12.80 percent). The lower limit of sensitivity for the progesterone standard curve was 0.3 ng. The lower limit of sen-sitivity for the estradiol-17β standard curve was 6 pg. The progesterone and estrogen concentrations were inversely related during the follicular phase and the late luteal phase period of the cycle. During the period of metestrus, the progesterone and estrogen concentrations increased simultaneously. An estrogen peak occurred on Day 0 in all groups. A secondary estrogen surge occurred five or six days post-estrus in Groups A, C and Do Normal follicles or follicles undergoing atresia may have contributed to both of these surges. The estrogen concentration in bred cows was significantly higher (P < 0.10) than the concentration in non-bred cows on Days 5, 6 and 10. This suggests that the zygote may be involved in regulating luteal phase estrogen secretion. The elevated estrogen levels on Day 5 and Day 6 may influence ovum trans-port in the oviducts or development of the uterine endometrium. The high estrogen level at Day 10 may be involved in preparing the uterus for implantation.

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