Masters Theses

Date of Award

12-1964

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Husbandry

Major Professor

Harold J. Smith

Committee Members

Charles S. Hobbs, R.L. Murphree

Abstract

Tennessee is predominantly a milk-fat spring lamb production area with some purebred production. These lambs are produced primarily by mating either native, western crossbred or fine-wool grade ewes to pure bred rams of mutton type, from the Hampshire, Suffolk and Southdown breeds. In the past, milk-fat spring lamb producers have preferred to sell their ewe lambs and to buy their replacement ewes from western sources rather than produce home-raised replacements. In general. western yearling ewes ready for breeding are less infected with parasites and can be obtained in large groups of uniform type, age, breed and size as compared to native ewes or home-raised replacements. In recent years, however, it has become increasingly more difficult to obtain western ewes of the desired breeding and quality. This has led many producers to consider the possibility of saving replacements from within the flock and has raised questions regarding the performance of ewes of grade and crossbred breeding, and various systems which might be used in producing replacement ewes.

Breeding or inherent genetic producing ability has economic significance to the producer for greater and more efficient production of lamb and wool. Both the breed of sire and breeding of the dam are important factors in producing lambs with superior growth and meat qualities. The qualities required in ewes for superior productivity are thriftiness, high prolificacy, good mothering ability, high milk production and satisfactory wool production. Ewes must produce a high percentage of twins with sufficient vigor to assure a high percentage of survival.

Grading up flocks from native or crossbred foundations or the use of a rotational crossbreeding program would offer two possibilities to the producer for producing replacement ewes.

Crossbreeding to improve market lamb production has been a major practice in the sheep industry of this country for many years. The pattern of crossbreeding differs considerably from section to section depending upon the environment and type of pasture and other conditions in the area. Planned crossbreeding is used mainly to evolve a type of sheep which is adapted to the particular environmental and economic conditions of the area. Studies have shown that crossbreeding increases fertility and prolificacy in ewes and livability in lambs. Three- and fo-ur-breed crosses have generally been superior in performance to purebreds, grades and two-breed crosses in terms of overall productivity. Previous research at the Tennessee Experiment Station has shown that the Northwestern crossbred Hampshire x Rambouillet ewe has performed well under Tennessee conditions, and superior in most respects to native ewes of mutton breeding. The grade Rambouillet ewe, although not as prolific as the Hampshire x Rambouillet ewe has also demonstrated certain advantages under Tennessee conditions.

The purposes of this study were: (l) to evaluate the performance and adaptability of high-grade and 2-breed and 3-breed crosses for spring lamb production; (2) to investigate the feasibility of producing stock replacement ewes within a flock, as compared to purchasing the ewes available from other sources; (3) to study the effectiveness of performance selection methods in improving productivity; and (4) to study the reproductive behavior and performance of commercial types of sheep.

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