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Linear Measurements and Visual Appraisal as Estimators of Percentage Empty Body Fat of Beef Cows¹

University of Minnesota, St. Paul 55108 and and Texas A&M University, College Station 77840

Abstract

Body compositions of 40 Angus, 20 Angus-Hereford and 20 Angus-Holstein spring-calving cows were determined by deuterium dilution at the initiation and at the end of the winter feeding period. For the winter feeding period, cows were allotted within breed to metaboliz-able energy (ME) levels of 12.9 or 18.0 Meal/ head daily. Weight (W), length, height, heart girth and condition score were measured on each cow before body composition determinations. Regressions were conducted within breed-body composition determination time groups to evaluate linear measurements and condition score as predictors of percentage empty body fat (PEBF) of beef cows. Regressions for Angus and Angus-Hereford cows were similar, but regressions for Angus-Holstein cows differed from those for Angus or Angus-Hereford cows. The best simple regression for the Angus-Holstein cows accounted for only 3% of the variation in PEBF. For the Angus and Angus-Hereford cows, condition score was the best estimator of PEBF (r = .66, P<.01). Weight: height ratio was correlated .58 (P<.01) with PEBF; however, weight alone was correlated .54 with PEBF. Regressions with W^2.0, W^.75 and W^.5 did not improve R² values over those obtained with W^1.0. Log and square root transformations of linear measurements did not improve ability to estimate PEBF. Multiple regressions did not significantly improve R² values over that of the simple regression of PEBF on condition score. Results of this study suggest that linear measurements are not superior to visual appraisal as estimators of body composition of beef cows.

¹ Paper No. 11,999 of the Scientific Journal Ser. of the Minnesota Agr. Exp. Sta.

² Dept. of Anim. Sci., Univ. of Minnesota, St. Paul 55108.

³ Dept. of Anim. Sci., Texas A&M Univ., College Station 77840.