Masters Theses

Date of Award

8-1977

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

John D. Smalling

Committee Members

William R. Backus, R. L. Murphree

Abstract

The objectives of this study were to: (1) identify the factors which are closely related to dystocia, (2) identify the degree of relationship between these factors, and (3) develop a practical system of predicting the occurrence of dystocia. One hundred and sixty-three primiparous beef heifers of Hereford or Angus breeding were studied at the Ames Plantation, Alcoa, Knoxville, and Oak Ridge stations. Data were collected on these heifers during the first, second and third trimester of gestation. Each heifer was observed and scored on the difficulty of her parturition. Measurements were taken on the calves within 24 hours of birth. Regression analyses were conducted to determine the relationship of the various measurements to the occurrence of dystocia. Of the factors which could be measured or otherwise calculated prior to parturition, the width of the pelvic canal of the heifer was indicated to be the most influential. The sire of the heifer was found to be the next most significant factor in this analysis. Following closely behind the sire of the heifer in rank of importance were: height of the pelvic canal and the pelvic area per day of age. Of the observations made postpartum, the length from hock to dew claws on the calf was the most closely correlated with dystocia. Following in order of relationship were: length of the cannon bone, width of the shoulders, width of the hips, and circumference of the heart girth of the calf. In evaluating the three data collection periods, the data collected at breeding accounted for a far greater percentage of the variability in dystocia than that collected at the other periods. In this study, the data collected at breeding defined a maximum of 87 percent of the total variability compared to 76 percent at pregnancy determination and 75 percent immediately prior to the calving season. It was not possible to designate one measurement which would predict dystocia to a satisfactory degree, using the limited number of observations available. Continued study on more heifers will be necessary. However, this study indicates that it may be possible to develop a technique which will enable cattlemen to accurately predict dystocia, at or before the time the heifer is bred.

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