Evaluation of factors affecting the performance of spring lambs

The predominant system of commercial sheep production in Tennessee is the production of milk fat spring lambs. Spring lamb is the term applied to the new crop of lambs arriving at the market in the spring, generally born in the early winter and winter months, and marketed directly off their dams. Spring pasture, favorable climate, breeding, care and management have contributed to the excellence of spring lamb production in Tennessee. The objective of the breeder in spring lamb production is to produce lambs with a fast rate of growth from birth to slaughter and a sufficient amount of fat to bring highest prices at the market. An understanding of the factors which influence the development and growth of sheep will suggest changes in the breeding and management system to improve productivity. Performance records and an effective selection program provides an important tool to the breeder to choose genetically superior animals for breeding purposes. Many non-genetic or environmental factors as well as genetic factors are known to influence the performance of sheep. Non-genetic factors hinder the breeder's effort to to select those animals having the greatest breeding value and reduce the progress which might be accomplished by selection. However, adjustments can be made where the effects of various environmental factors are known in order to evaluate and place the records of animals on a more comparable basis. The objectives of this study were to determine the productivity of ewes of different breeding and to evaluate the effect of various factors including breeding of dam, age of dam, month of birth, sex of lamb, type of birth and type of rearing on various lamb performance traits.