Evaluation of phenotypic and genetic trends in weaning weight in Angus and Hereford populations in Virginia

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dc.contributor.authorNadarajah, Kanagasabaien
dc.contributor.committeechairMarlowe, T.J.en
dc.contributor.committeememberNotter, David R.en
dc.contributor.committeememberPearson, R.E.en
dc.contributor.committeememberHinkelmann, Klausen
dc.contributor.committeememberEller, Arthur L. Jr.en
dc.contributor.committeememberSwiger, L. Andyen
dc.contributor.departmentAnimal Science (Animal Breeding and Genetics)en
dc.date.accessioned2017-01-30T21:24:02Zen
dc.date.available2017-01-30T21:24:02Zen
dc.date.issued1985en
dc.description.abstractTotal weaning weight records of 29,832 Angus and 15,765 Hereford calves born during 1953 through 1983 in Virginia were used to evaluate phenotypic and genetic trends for adjusted weaning weight (AWWT), weaning weight ratio (WWR) and deviation of AWWT from the mean AWWT of the contemporaries (DEVN). Two approaches, namely the regression techniques and maximum likelihood (ML) procedure were taken to estimate the above trends. The estimates of annual phenotypic trend for AWWT in the Angus and Hereford breeds were .96 and .82 kg/yr, respectively. The sire and dam genetic trends obtained from both approaches for the traits of interest were positive and significant; however, the estimates from the regression analyses were slightly higher than those- from the ML procedure. The estimates of one-half of the sire genetic trends obtained from ML procedure for WWR and DEVN were .40 ± .04 ratio units/yr and .72 ± .07 kg/yr in the Angus breed and the corresponding values for the Hereford breed were .25 ± .06 ratio units/yr and .45 ± .12 kg/yr. The estimates of one-half of the darn trends for the corresponding traits were .32 ± .02 ratio units/yr and .55 ± .04 kg/yr for Angus and .21 ± .03 ratio units/yr and .30 ± .07 kg/yr for Herefords. The application of adjustment factors (to eliminate the bias due to non-random mating and culling levels) to estimates of sire genetic trends in the regression analyses produced estimates more similar to the estimates obtained from the ML procedure. The average annual genetic trends over the study period from the ML procedure for AWWT were 1.27 kg/yr for Angus and .75 kg/yr for Herefords.en
dc.description.degreePh. D.en
dc.format.extentix, 112 leavesen
dc.format.mimetypeapplication/pdfen
dc.identifier.urihttp://hdl.handle.net/10919/74717en
dc.language.isoen_USen
dc.publisherVirginia Polytechnic Institute and State Universityen
dc.relation.isformatofOCLC# 13174978en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V856 1985.N322en
dc.subject.lcshAberdeen-Angus cattleen
dc.subject.lcshHereford cattleen
dc.subject.lcshBeef cattle -- Genetics. -- Virginiaen
dc.subject.lcshBeef cattle -- Weights and measures. -- Virginiaen
dc.titleEvaluation of phenotypic and genetic trends in weaning weight in Angus and Hereford populations in Virginiaen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineAnimal Science (Animal Breeding and Genetics)en
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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