Genetic evaluation of a linear trait description

dc.contributor.authorSchaeffer, George Barryen
dc.contributor.departmentDairy Scienceen
dc.description.abstractData for this study were 79,997 evaluations for 12 individual body and udder traits of Holstein cows. Type scores were subjectively assigned by trained personnel of Select Sires, Inc., Plain City, OH, through their corrective mating and young sire evaluation programs. After editing data to remove incomplete, erroneous and duplicate records, 56,642 records were used to calculate overall and regional age adjustment factors. Genetic parameters were estimated. Heritabilities ranged from .40 for stature to .14 for fore udder. Standard errors ranged from .039 for stature to .018 for fore udder. Genetic correlations ranged from +.75 between teats and udder support to -.61 between feet and legs. Phenotypic correlations were generally smaller than genetic correlations, ranging from .56 between udder support and teats to -.23 for dairyness and strength. These findings were in general agreement with previous research. Genetic evaluations for the 12 individual linear traits were made using Herdmate Comparison (HC) and Best Linear Unbiased Prediction (BLUP) methods. Mean evaluations by HC were near zero, and ranged from .026 for stature to -.027 for teats. Mean repeatability also showed very little variation, ranging from .404 for stature to .241 for teats. BLUP evaluations were similar to HC evaluations, with mean evaluation ranging from .121 for feet to -.183 for dairyness. Direct correlations between BLUP and HC evaluations ranged from .90 for stature to .74 for dairyness. Forty-eight different combinations of minimum daughter numbers and model variables were tested to predict sires' overall evaluations for type from linear trait evaluations using regression analysis. Results indicate that with 5 or more daughters per sire, all predictions tested were similar in accuracy for Predicted Difference for Type.en
dc.format.extentviii, 100 leavesen
dc.publisherVirginia Polytechnic Institute and State Universityen
dc.relation.isformatofOCLC# 12111403en
dc.rightsIn Copyrighten
dc.subject.lccLD5655.V855 1985.S323en
dc.subject.lcshCows -- Geneticsen
dc.subject.lcshDairy cattle -- Geneticsen
dc.titleGenetic evaluation of a linear trait descriptionen
dc.type.dcmitypeTexten Scienceen Polytechnic Institute and State Universityen
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