Relationship among Definable Characteristics of Feeder Calves, Subsequent Performance and Carcass Traits. II. Subjective Scores

Abstract

Three-hundred and forty-nine commercial calves of Angus, Hereford, Charolais-cross and Angus × Hereford breeding were fed to an estimated constant subcutaneous fat thickness (12 mm) on high and medium energy diets. Physical description of feeder calves, in terms of subjective scores for frame, fat and muscle, combined with initial calf weight and breed classification, explained 49% of the variation in carcass weight within diet-year subclasses and 32% of that in days on feed. Deletion of subjective scores from the models reduced coefficients of determination for carcass weight and days on feed by 13 and 5%, respectively. Corresponding reductions from deletion of terms for breed were 9 and 11%. Among descriptive variables (listed in order of magnitude of partial mean-squares), frame (P<.001), breed (P<.001), initial weight (P<.05), fat (P<.05) and frame × breed (P<.05) were sources of variation in carcass weight; while breed (P<.001), frame × diet (P<.01) and fat (P<.01) were related to days on feed. In general, frame was positively related and fat negatively related to carcass weight and days on feed. Effects of frame were similar to those of measured wither height and body depth, and subjective fat was less related than ultrasonically measured fat to response variables. Coefficients of determination from models describing yield and quality grades were .11 and .07, respectively. Muscle was unrelated (Pώ.05) to response variables studied.