Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Dairy Science


The process of birth normally follows a set pattern. The main steps in chronological order are: labor, opening of the cervix, and delivering the young. The cervix serves an important function in reproduction. The cervix is the constricted portion separating the uterus and the vagina, and consists primarily of thick connective tissues especially constructed in folds forming a hollow tube. Through the cervix passes sperm, menstrual debris and in pregnancy the newborn. During pregnancy a mucous plug forms in the cervix and keeps out foreign material and bacteria. In the non-pregnant cow the opening is small. The cervix opening is constricted enough so that difficulty in inserting an artificial insemination tube sometimes occurs. If ova transfer can be perfected to the degree that artificial insemination is today, a revolutionary way of up-breeding a herd of cattle may result. In order for ova transfer to fulfill this role a non-surgical method of extracting and implanting must be perfected. If a non-surgical method is to be used, entrance into the uterus through the cervix is paramount is to be used, entrance into the uterus through the cervix is paramount the non-surgical equipment used to collect the ova is considerably larger than an artificial inseminating tube. Passage through the cervix with this equipment is accomplish with extreme difficulty. The inaccessibility of the uterus resulting from constriction of the cervix has markedly hampered the development of ova transfer. If the cervix can be dilated so as to allow easy entrance into the uterus, ova transfer may become of practical value in the not too distant future. A dilated cervix would allow larger and more precise collecting instrument to be used. Parturition is facilitated in some rodents by the action of relaxin upon the symphysis pubis and pelvic bones. Relaxin is a female hormone secreted by the placenta, uterus and ovaries and is present in the blood during gestation of many animals. Relaxin apparently has two purposes in the human uterine quiescence during gestation and dilation of the cervix at parturition. The use of relaxin to dilate the cervix in human suggested the possibility that dilation of the bovine cervix may be obtained by the administration of relaxin. To further investigate the physiological properties of the cervix and the possibility of dilation in the non-pregnant cow, the following experiment were conducted. 1 The effect of relaxin upon the cow’s cervix while in estrus. 2 The effect of liquid and depot relaxin upon the cow’s cervix when primed with stilbestrol. 3 The effect of blood from a cow in labor, transfused into a non-pregnant, non-estrus recipient. The milk letdown response just prior to parturition suggests that the hormones probably are influential and effective at this time. Oxycontin is known to contract the alveolar and force milk into the collecting ducts, gland cisterns, and test sinuses. Relaxin is likewise believed to be present in quantity at parturition and might have a contraction effect on the myoeptithelium around the alveoli. To determine if such action might be possible in the lactating cow, a series of experiments were conducted to determine the effect of relaxin on milk letdown.

Library of Congress Subject Headings

Cattle -- Breeding.
Muscle relaxants.


Includes bibliographical references (pages 36-43)



Number of Pages



South Dakota State University


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Dairy Science Commons