Masters Theses

Date of Award

3-1956

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Husbandry

Major Professor

Charles S. Hobbs

Committee Members

Harold J. Smith, Lawrence N. Skold

Abstract

The increasing frequency of dwarfs in recent years seems to indicate that carrier individuals have been favored in the selection of breeding stock, although experimental evidence to confirm this is lacking. The cause of this trend in selection is not known; therefore, many recent research investigations have been conducted to try to find methods to detect carrier animals. One method for the identification of dwarf carriera proposed by L. N. Hazel of Iowa State College involves taking X-ray pictures of the lumbar vertebrae of young calves to be used in classifying the animals into non-carrier, carrier and dwarf types on the basis of the presence and/or absence of certain vertebral abnormalities.

ln 1954, the University of Tennessee, in cooperation with lowa State College, began research on the problem of methods of distinguishing between non-carrier and carrier cattle. High (1955) presented results of the first year’s work in which three known carrier bulls were mated to cow herds thought to be relatively free of the dwarf gene. The progeny were X-rayed and classified into non-carrier, carrier and dwarf types on the basis of lumbar X-ray exposures. He reported that the ratio of non-carrier to carrier in the progeny of one bull deviated somewhat from the expected 50:50 ratio, but was well within the limits of chance. The ratios (carriers to nm-carriers) among the progeny of the other two bulls were approximately the same as expected. High (1955) also presented results of a study of the relationship of various body measurements to genotypes for bovine dwarfism as estimated from X-rays of the lumbar vertebrae. The results of this study indicated that presumed carrier animals (by X-ray determination) exhibited superiority in some desirable beef cattle characteristics.

The purpose of this paper is to present the results of further studies on tha value and interpretation of the X-ray techniques in the identification of carriers of the dwarfism gene.

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