Growth performance, body composition, carcass traits and meat quality of young Nellore bulls fed freshly cut or ensiled sugar cane

The objective of this study was to compare the effects of diets with two levels (20 and 50% dry matter (DM) basis) of sugar cane (Saccharum officcinarum), either chopped fresh or ensiled with calcium oxide (CaO) and Lactobacillus buchneri as additives, in combination with two concentrate levels (80 and 50% DM basis) on the animal performance, body composition and gains, carcass characteristics and meat quality of young Nellore bulls. Treatments were arranged in a 2 × 2 factorial design: 50% freshly cut sugar cane +50% concentrate, 20% freshly cut sugar cane +80% concentrate, 50% sugar cane silage +50% concentrate and 20% sugar cane silage +80% concentrate. Twenty-nine Nellore bulls (300 ± 4.8 kg BW) were used; five bulls were slaughtered at the beginning of the experiment and used as reference animals. Bulls remained in the feedlots for 84 days after an adaptation period of 25 days. The interaction of roughage and concentrate was significant for dry matter intake, daily gain of body weight fasting, daily gain of empty carcass weight, daily gain of carcass, slaughter weight and weight of carcass. Dry matter intake was greater in bulls receiving freshly cut sugar cane. Daily gain of carcass, slaughter weight and carcass weight were lower in bulls fed 50% sugar cane silage +50% concentrate. There were no differences in carcass yield (P = 0.4027) and loin eye area (P = 0.1005) among the treatments. Backfat thickness was greater (P = 0.0406) with 80% concentrate. The interaction of concentrate level and roughage type was significant for daily gain of fat and energy, with lower values for bulls fed 50% sugar cane silage +50% concentrate. Thawing (P = 0.0149), cooking (P = 0.0352) and total losses (P = 0.0059) were greater in diets that contained sugar cane silage. There was an increase in shear force (P = 0.0103) and a decrease in sarcomere length (P = 0.0061) in bulls fed sugar cane silage, although they remained within the limits that characterized the flesh as soft. Diet was not found to affect the myofibrillar fragmentation index, color index (L*, a* and b*) or the amount of collagen (total and soluble) in beef. Ensiled sugar cane combined with 50% concentrate in bulls fattening in feedlots yielded lower animal performance than 80% concentrate and diets containing freshly chopped sugar cane with 50 and 80% concentrate levels.