Carcass Characteristics of Nellore Cattle Submitted to Either Nutritional Restriction or Intake of Concentrate Feedstuffs Prior to Adaptation Period

The study, conducted at São Paulo State University feedlot, Dracena campus, Brazil, was designed to evaluate the effects of either nutritional restriction or intake of concentrate feedstuffs before beginning the adaptation period on carcass characteristics of Nellore cattle. The experiment was designed as a completely randomized block, replicated 8 times (4 animals/pen), in which 96 22-mo-old yearling Nellore bulls (365.5 ± 39.2 kg) were fed in 24 pens according to the treatments: Restriction (Tifton hay fed at 1.4% of BW + mineral supplement); Control (Tifton hay fed ad libitum + mineral supplement) and Concentrate (Tifton hay fed ad libitum + 0.5% of BW of a mix of concentrate feedstuffs and mineral supplement). This study lasted 144-d, divided into 2 periods: 32-d of pre-adaptation, in which cattle were submitted to the treatments previously described, and 112-d of feeding high-concentrate diets, where cattle were fed the same diets. The adaptation program consisted of ad libitum feeding of two diets over adaptation period with concentrate level increasing from 72% to 86% of diet DM. The finishing diet contained: 73.5% cracked corn grain, 14.0% sugarcane bagasse, 9.0% cottonseed meal, 1.5% supplement, 1.2% urea and 0.8% limestone (DM basis). Cattle were fed ad libitum three times daily throughout the study. At the end of pre-adaptation period, one animal per pen was slaughtered (n= 24) for carcass evaluations, and the remaining 72 animals were harvested after 112-d of feeding high-concentrate diets. No significant (P > 0.10) treatment effect was observed for final dressing percentage, and initial and final marbling scores. Cattle submitted to nutritional restriction had lighter (P < 0.10) initial HCW in kg (Restriction= 183.43^c, Control= 187.41^b, Concentrate= 193.96^a), smaller initial LM area in cm² (Restriction= 49.31^b, Control= 51.59^a, Concentrate= 53.14^a), and decreased initial dressing percentage (Restriction= 48.52^c, Control= 48.60^b, Concentrate= 48.78^a) and initial 12^th rib fat thickness in mm (Restriction= 2.10^b, Control= 2.24^a, Concentrate= 2.34^a). Nevertheless, cattle submitted to nutritional restriction compensated during the period of feeding high-concentrate diets the negative impact of restriction and presented similar (P < 0.10) final HCW in kg (Restriction= 285.35^a, Control= 274.10^b, Concentrate= 287.30^a), carcass ADG in kg (Restriction= 0.92^a, Control= 0.77^b, Concentrate= 0.83^ab) and final 12^th rib fat in mm (Restriction= 6.14^a, Control= 5.23^b, Concentrate= 5.91^a) when compared to cattle submitted to intake of concentrate. Thus, cattle should be submitted to nutritional restriction or intake of concentrate feedstuffs before the adaptation period to improve overall carcass characteristics.