Characteristics of non integrate body components of carcass of steers and young steers of different genetic groups

The objective of this trial was to evaluate the components of non integrate body components of carcass of two categories, steers (slaughtered at 22.8 months old) and young steers (slaughtered at 15.2 months old), from two genetic groups, 5/8 Charolais (CH) 3/8 Nellore (NE) and 5/8NE 3/8CH, and to evaluate the relationship among the variables studied. The animals were fedlot finished until reaching 430 kg. The diet, roughage: concentrate ratio of 60:40 (dry matter basis), contained 10.25% crude protein and 3.18 Meal of digestible energy/kg of dry matter. The experiment was analyzed as a complete randomized design with six replicates, according to a 2 x 2 (two categories x two genetic groups) factorial scheme. Slaughter weight (SW) and empty body weight (EBW) were similar between categories and between genetic groups. When the components were expressed as absolute values and adjusted for EBW and SW, steers showed higher heart, liver, empty omasum and total vital organs weights, and young steers showed higher rawhide, kidney fat, trim fat and total internal fats weights. While 5/8CH 3/8NE showed higher liver, kidney fat, total vital organs and blood weights, and 5/8NE 3/8CH higher rawhide and total external components weights. When adjusted for EBW, steers showed higher weights of components lung, empty rumen+reticulum and total empty digestible tract, while 5/8CH 3/8NE showed higher total empty digestible tract weight. Each kg of intermuscular fat deposited in the carcass represented increase of 0.006 points in slaughter body condition score, 0.113 mm in subcutaneous fat thickness, 0.253 kg in ruminal+visceral fat, 0.089 kg in kidney fat, 0.076 kg in trim fat and 0.040 kg in inguinal fat. Positive relation was verified among requirement of net energy for maintenance and weight of vital organs components.