Technical note: chemical composition of Angus and Holstein carcasses predicted from rib section composition

Seventy-four small-framed Angus and sixty-nine Holsteins were used to evaluate the classic Hankins and Howe equations for predicting percentages of water, protein, and lipid of steer carcasses varying in weight and breed type. Animals were fed either corn grain or corn silage diets, housed inside or outside, and slaughtered at one of five predetermined weights within breed. Soft tissues from a carcass side and the from the 9-10-11th rib section were separated from bone, and the percentages of water, protein, and lipid were measured. The Hankins and Howe equations predicted .81 +/- .181 percentage units more (P < .001) water and .99 +/- .213 percentage units less (P < .001) lipid than was measured in the carcasses. The residual difference for protein depended on breed and diet (P < .028) and decreased .22 +/- .078 percentage units for each percentage unit increase in predicted protein. During development of equations from our data, no statistical difference was found between Angus and Holstein in the relationship of carcass water to rib water. The relationship of carcass protein to rib protein had a lower (P < .1) intercept with a steeper (P < .055) slope for Angus than for Holstein steers, whereas for lipid there was no difference between the slopes, but Holsteins had one percentage unit more (P < .038) carcass lipid than Angus at the same percentage rib lipid. These results confirm that composition of the 9-10-11th rib section can be used accurately to predict carcass composition with minor adjustments for breed type.