Evaluation Of Live And Ultrasound Measures As Estimators Of Performance Traits In Young Beef Bulls

Robert Brooks

Date of Graduation

Summer 2002

Degree

Master of Natural and Applied Science in Agriculture

Department

College of Agriculture

Committee Chair

Thomas Perkins

Abstract

Live measures were collected from 641 beef bulls at a performance test station. Ultrasound carcass measures were obtained utilizing 214 bulls from this study. Breed-types represented in this study included Beefmaster (BM, n=155), Santa Gertrudis (SG, n=389), Brahman (BR, n=30), Simbrah (SI, n=28), and all other breeds (OB, n=39). Prediction equations were developed for end of test live measures of hip height (FHH), scrotal circumference (FSC), and body weight (FLWT), as well as carcass measures of longissimus muscle area (FLMAU) and 12th rib fat thickness (FFTU). Prediction equations for FLWT were characterized by high coefficients of determination ranging from .88 to .93. Prediction equations for FLMAU were distinguished by r² values ranging from .35 to .55. Age constant measures of FLMAU yielded more accurate prediction equations than weight constant measures or actual FLMAU. Accuracy of equations for FHH, FSC, and FFTU was highly variable between breed-types. These findings indicate that development of age or weight adjustment factors may be necessary to allow accurate comparisons of performance traits of animals within contemporary groups.

Subject Categories

Agriculture

Copyright

© Robert Brooks

Citation-only

Dissertation/Thesis

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