Masters Theses

Date of Award

12-1965

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Husbandry

Major Professor

S.A. Griffin

Committee Members

H.J. Smith, Haley M. Jamison

Abstract

A good deal of progress has been made in improving the productivity of sheep through selection of performance-tested and progeny-tested breeding animals in recent years. The ram represents one-half of the sheep flock. Thus careful selection of high producing rams which will sire fast-gaining and good-type lambs of desirable market quality is of importance. There has been considerable emphasis on intrinsic qualities of the individual, the performance merit of families and the value of proven sires with ability to transmit their superior characters to their offspring. The best and most reliable method of accomplishing greater production in a reasonable period of time is through selection and breeding of superior producing animals. A new approach to make selection more effective is by the collection and use of accurate records of performance on prospective breeding rams as a supplement to the practice of selecting rams by visual appraisal, as it is impossible or impractical to collect records on every animal.

The performance record on prospective breeding rams is a most valuable and useful technique in continued flock improvement through selection of performance-tested and progeny-tested rams. The data affords an opportunity to eliminate undesirable traits and to evaluate the quality and performance of sheep due to differences in inherent potential. These differences cannot be predicted accurately by visual selection because of variation in environment and genetic makeup. Studies that involve high-performing rams indicate that they are capable of siring lambs of considerably greater value than those sired by low-performing rams.

Breeding experience has shown that the most important consideration in lamb selection should be individual performance. Performance testing is a great aid in selecting high-producing rams, capable of transmitting maximum performance to their progeny, at an early age with a high degree of accuracy. It has been observed that a ram which produces good lambs one year usually continues to do so throughout his working life. Progeny testing is an accurate way of selecting, but, unfortunately, it is slow. Even if a progeny testing program is followed with prospective stud rams before they are used in the main flock, only a small percentage of the most promising rams can be progeny tested. Hence performance testing of rams is often used to determine the importance of individual merit of rams when used in breeding programs. Performance testing provides a safe and solid stepping stone towards the improvement of production efficiency and better profits of sheep through early selection of high-producing animals.

The main purposes of this study were;

1. To evaluate various performance criteria for selection of rams on the basis of the relative effects of various factors such as sex, type of birth, age of dam, season of birth, and rearing on birth weight and birth to weaning weight, grades and post-weaning performance;

2, To determine the improvement in quality and quantity of lamb and wool through the selection of performance tested rams; and

3. To determine the relationship of performance records taken at different times during the growing period.

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