| Sixty-four Holstein castrated males were randomly assigned to four groups of 16 animals; each group corresponded to a slaughter age of 3, 6, 9, or 12 months of age. The assignment of animals was performed in groups of eight, every season during two years. The urea dilution technique was performed 48 hours before slaughter. After slaughter, carcass specific gravity was determined on the right side of the carcass, and the 9-10-11{dollar}sp{lcub}rm th{rcub}{dollar} rib cut was separated from the left side to determine its composition. The relationships between urea space (kg, %EBWT, and %LW), LW, and EBWT and edible carcass composition (protein, fat, moisture, and ash, expressed in percentage and in kg) were studied. One and two-pool models were fitted using the urea dilution data, and the coefficients (A = coefficient of first pool, B = coefficient of second pool, and Co = A + B (zero time concentration)) were used to estimate body volume. Carcass specific gravity and the rib cut composition were used individually as predictors of edible carcass composition. Live weight and EBWT effectively predicted the amount of water, fat, and protein in edible carcass. Correlation coefficients between urea space and edible carcass water, expressed in kg, for the pooled data ranged from 0.48 at 42 min to 0.74 at 6 minutes after infusion. The biexponential model coefficients explained more variation of edible carcass composition than urea space did. Correlation coefficients for volume B and edible carcass components were.78,.68,.69, and.76, for water, fat, ash, and protein, respectively. The relationships between volume A and edible carcass components were weaker than those for volume B (water =.59, fat =.51, ash =.58, and protein =.59). The highest correlation coefficients were obtained when Co was used for water, fat, ash, and protein (.83,.70,.74, and.81, respectively). Equations combining LW, EBWT, and the two-pool model coefficients explained much of the variation of edible carcass composition. Carcass specific gravity did not accurately estimate edible carcass composition, obtaining maximum r{dollar}sp2{dollar} lower than.35. The rib cut method predicted edible carcass composition more accurately than carcass specific gravity and urea space, when equations were calculated with the pooled data and expressed in kg. Coefficient of determination for water, fat, ash, and protein were.95,.86,.54, and.96, respectively. |
