Relationships among Various Body Components of Mature Cows

Abstract

Mature (9-yr-old), nonpregnant, nonlactating Angus X Hereford and the reciprocal cross (AHX, 12), Charolais X Angus or Hereford (CX, 11), Jersey X Angus or Hereford (JX, 11) and Simmental X Angus or Hereford (SX, 12) cows that had been fed either a low (112 kcal X kg-.75 X d-1), medium (178 kcal X kg-.75 X d-1) or high (ad libitum) level of metabolizable energy (ME) intake for 140 d were used to evaluate relationships among various body components. Live weight, hip height, backfat and condition score were determined on d 140. Before slaughter, each cow was infused with deuterium oxide (D2O; .25 g/kg live weight) and serial blood samples were taken. Traits evaluated after slaughter were hot weight of each carcass half, hide weight, viscera weight, longissimus muscle area, fat thickness, kidney, pelvic and heart fat percentage and marbling score. Offal and carcass chemical compositions were determined and empty body composition was calculated. Moderate to high (R2 = .82 to .97) coefficients of determination were obtained when weight of empty body chemical components were regressed on live animal or carcass cooler measures. Correlations between percentage carcass or empty body water and percentage of fat, fat-free organic matter or energy, or between amount of carcass or empty body water and amount of fat-free organic matter were high (R2 = .83 to .99). Weight of carcass or empty body water was not highly related (R2 = .05 to .22) to the total amount of fat or energy. Similar results were obtained when amount of empty body components were regressed on D2O spaces alone. Inclusion of empty body weight (or live weight) in equations relating D2O spaces to weight of the empty body or chemical components resulted in R2 values of .86 to .99. Carcass composition, as expected, was more highly related to empty body composition than was offal composition. Empty body composition was not highly related to empty body weight.