Masters Theses

Date of Award

8-1965

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Husbandry

Major Professor

H.J. Smith

Committee Members

L.L. Christian, E.R. Lidvall Jr

Abstract

Increased efforts to improve performance characteristics in swine has prompted producers to take a closer look at the effects of cross breeding. Success obtained with hybrid com has led many to believe that beneficial results might be expected from crossbreeding swine. Cross breeding for production advantages in market animals has been in practice for several years, especially swine and sheep. Its use has been opposed by a few breeders who contend that continuous usage will result in lowering of the general quality of livestock. Swine producers are seeking a market hog capable of rapid and economical conversion of feed into pork. Improved performance through expression of heterosis should aid in the attainment of this goal. Experimental work indicates that heterosis results from the mating of genetically divergent animals. Heterosis effects are demonstrated in the offspring through larger litters, greater viability and faster gains. Reliable systems of obtaining some degree of heterosis are: (1) straight breeding, the mating of unrelated animals within a breed; (2) cross breeding, the crossing of different breeds; (3) linecrossing, the crossing of inbred lines within breeds; and (4) linecrossbreeding, the crossing of inbred lines of different breeds. Considerable research data is available on crossbreeding in swine, and its usefulness in commercial swine production has been widely accepted. However, there is limited research work to support which of the various breed crosses produce the greater advantage in the important economic traits. Heritability estimates indicate that improvement in the important economic performance traits of swine should be attained through selection (Craft, 1958). and age of dam, hamper the breeder's ability to select those animals There is a need for more detailed Environmental and other factors, such as season of birth having the greatest breeding value, information on the magnitude and extent of these effects so that performance records can be more accurately adjusted before selections are made. The objectives of this study were: (1) to compare certain litter performance traits of pigs produced by straightbreeding and crossbreeding; (2) to compare the relative performance of straightbred with two- and three-breed crosses and to attempt to determine the more desirable breed crosses; and (3) to study the effect of age of dam and season of birth on litter performance traits.

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