After 140 lb, feed intake increases more slowly. Barrows have both higher daily growth rates and feed intakes than gilts. Protein accretion includes the protein in all body components including the head, carcass, visceral organs, feet, skin and bone. Carcass fat-free lean is the total dissected carcass muscle tissue minus the fat contained within the dissected muscle. The growth curves for lean gain and protein accretion are similar.
Muscular pigs have a higher ratio of lean gain to protein accretion than less muscular pigs.
Prediction equations for fat-free lean place more emphasis on loin eye area measurements than the empty body protein accretion prediction equations. For these reasons, the protein accretion and fat-free lean curves from different sexes and genotypes are slightly different. Daily protein accretion and lean growth rates increase and reach maximum at 120 to 160 lb. After 160 lb, daily lean gain and protein accretion decline. The protein accretion rates of barrows and gilts are similar.