Abstract
Ninety-six Yorkshire pigs, reared during the growing period on high energy–high protein rations, were used in a 2 × 2 factorial feeding experiment to compare two levels of protein at two levels of energy in self-fed finishing rations. Pigs fed a high energy ration gained 0.34 lb more per day, consumed less feed, had more loin and back fat, lower Record of Performance (R.O.P.) scores, and received lower commercial grades than those fed the lower energy ration. The level of protein fed did not affect significantly, rate of gain, feed utilization, or carcass quality. An interaction existed between protein and energy whereby the adverse effects on carcass quality of the high level of energy were modified by the high level of protein with the result that average loin area was increased and a higher R.O.P. score and a higher percentage of grade A carcasses was obtained.