An Evaluation of the Endocrine Response to Dystocia in the Primiparous Cow and Calf

Authors

Glenda M. Borcher

Date of this Version

Fall 8-1992

Comments

A Thesis Presented to the Faculty of The Graduate College in the University of Nebraska In partial Fulfillment of Requirements For the Degree of Master of Science Major: Animal science

Under the supervision of Professor Edgar T. Clemens

Abstract

Parturition is a very stressful event for both the cow and the calf. Endocrine changes occur which typically enable to calf to make the transition from a uterine to a gaseous environment. These endocrine changes are basic stress responses, necessary for an organism to maintain homeostasis. They include surges in catecholamine and cortisol secretion and changes in T3 secretion in response to temperature changes. It is well established that the stress response, if

prolonged, can become detrimental. Prolonged stress can result in muscle wasting, immune impairment and gastrointestinal ulceration. If parturition is delayed or particularly stressful due to environmental factors I the endocrine stress response may become detrimental to the fetus and the neonate. The catecholamine epinephrine is associated with hypertensive ulcers. Epinephrine stimulates the release of gastrin which stimulates the release of gastric acid in the stomach. This study was set forth as an attempt to evaluate the level of stress associated with parturition and to identify the nature of the relationship between epinephrine, norepinephrine and gastrin. In this study, epinephrine levels increased with the level of dystocia and an interaction between gastrin and epinephrine was identified in the calves at birth. As epinephrine levels increased over all concentrations of gastrin, there was an increase in calving score. This interaction resulted in the largest calving score at intermediate levels of gastrin (300 pg/ml) and calving score fell as gastrin levels increased. However, the differences observed at birth were not apparent when the calves were 24 hours old. The results of this study also suggest that there may be a relationship between the level of T, and dystocia. Calves with larger calving scores exhibited a lower T, secretion, even at 24 hours of age. This may indicate an impairment of the calves' ability to thermoregulate and may be an important factor in calf survival.