Document Type

Thesis - Open Access

Award Date

1968

Degree Name

Master of Science (MS)

Department

Animal Science

Abstract

There were 1,642,000 beef cows in South Dakota on_ January 1, 1967, which was 14 percent higher than the 1961-65 average (South Dakota Crop and Livestock Reporting Service, 1967). These cows were valued at $307, 054, 000, a 27 percent increase over the 1961-65 average. There were 390, 000 head of cattle and calves on feed on January 1, 1967, a 33 percent increase over 1961 and a 22 percent increase over the 1961-65 average. The sale of cattle and calves has accounted for 44 percent of the cash farm income in South Dakota for the period 1958-65 and is the largest farm enterprise even allowing for the fact that a good share of the crops produced are marketed through beef cattle. The per capita consumption of beef in the United States for the period 1961-66 was 95 pounds, more than all other red meat combined. These statistics indicate the importance of the beef cattle industry to the state of South Dakota. Any improvement in beef cattle performance or in the quantity and quality of the meat produced would benefit the entire industry from rancher to consumer. Increasing costs of producing beef and the real possibility of competition from meat substitute products should make all segments of the beef cattle industry concerned about ways they can improve their product. One of the ways to improve beef cattle traits is through selection. The progress that can be made through selection for a certain trait is equal to the heritability of the trait times the selection differential. The selection differential is defined as the difference between the average of the selected animals and the average of the population from which they came. This is largely dependent on the proportion of animals needed for replacements. Heritability refers to that portion of the observed phenotypic variation due to heredity and in a narrow sense includes only the average effects of the individual genes. The relationship between two traits observed directly is the phenotypic correlation. The environmental correlation.is a measure of the effects common to both traits that originate from environmental effects or non-linear gene effects. A genetic correlation defines the relationship between two traits which.is due to common genie action of one or more genes. The genetic correlation between two traits is used to determine correlated response. Correlated response is the change in one trait resulting from selection applied to another trait. Correlated response can be either desirable or undesirable depending on the traits involved and the sign of the genetic correlation. Another way to improve beef cattle traits then is to take advantage of desirable correlated response. The major objectives of this study were to estimate the heritability of beef cattle traits and the genetic, phenotypic and environmental correlations among them.

Library of Congress Subject Headings

Beef cattle
Beef cattle -- Carcasses

Format

application/pdf

Publisher

South Dakota State University

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