Feedlot Performance of Nellore Cattle Submitted to Either Nutritional Restriction or Intake of Concentrate Feedstuffs Prior to Adaptation Period

The study was conducted at the São Paulo State University feedlot, Dracena campus, Brazil. It was designed to compare the effects of nutritional restriction or intake of concentrate feedstuffs before the adaptation period on feedlot performance of Nellore cattle. The experiment was designed as a completely randomized block, which was 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, and 112-d of feeding high-concentrate diets, during which all cattle were fed the same diet. The adaptation program consisted of ad libitum feeding of two diets during the adaptation period with the 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. No significant treatment effect was observed for days to adapt to the finishing diet (Restriction = 14.6-d, Control = 14.9-d, Concentrate = 14.5-d). Nevertheless, cattle submitted to intake of concentrate tended to have greater (P < 0.10) initial BW (Restriction = 376.23^c, Control = 384.06^b, Concentrate = 397.21^a kg) at the beginning of the adaptation period, and also greater final BW (Restriction = 520.17^ab, Control = 503.23^b, Concentrate = 529.84^a kg) than cattle in the control group at the end of the study. Cattle submitted to nutritional restriction had greater ADG (Restriction = 1.29^a, Control = 1.06^b, Concentrate = 1.18^ab kg/d), DMI (Restriction = 9.19^a, Control = 8.56^b, Concentrate = 8.86^{ab kg/d}), and DMI expressed as % of BW (Restriction = 2.06^a, Control = 1.94^b kg, Concentrate = 1.91^b) than cattle in gthe control group. Likewise, cattle submitted to nutritional restriction had higher G:F ratios (Restriction = 0.140^a, Control = 0.124^b, Concentrate = 0.133^ab) during the period of feeding high-concentrate diets when compared to cattle on control group. Thus, cattle should be submitted to nutritional restriction or intake of concentrate feedstuffs before the adaptation period to improve overall feedlot performance.