Feedlot performance, feeding behavior, carcass characteristics, rumen and cecum morphometric of Nellore cattle submitted to either nutritional restriction or intake of concentrate feedstuffs before beginning the 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 days to adapt, feedlot performance, feeding behavior, carcass characteristics, rumen and cecum morphometric of Nellore cattle. The experiment was designed as a completely randomized block, replicated 8 times (4 animals/pen), in which 96 Nellore bulls with initial body weight (BW) 365.52 ± 39.19 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. At the end of pre-adaptation period, one animal per pen was slaughtered (n = 24) for carcass, cecum and rumen 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 days to adapt to finishing diet, that was 14 days. Cattle submitted to intake of concentrate had greater (P < 0.10) final BW, average daily gain (ADG), dry matter intake (DMI), hot carcass weight (HCW), dressing percentage, 12th rib and Biceps femoris fat thickness, and also better feed to gain ratio (F:G) and gain to feed ratio (G:F) than cattle on control group at the pre-adaptation period. However, cattle submitted to nutritional restriction had greater (P < 0.10) ADG, DMI, F:G, G:F, number of papillae and absorptive surface area than cattle on control group at the feeding high-concentrate diets period. Cattle submitted to nutritional restriction or intake of concentrate feedstuffs had greater (P < 0.10) final HCW, 12th rib and Biceps femoris fat thickness and longissimus muscle area gain than cattle on control group at the end feeding high-concentrate diets period. Either nutritional restriction or intake of concentrate feedstuffs before beginning the adaptation period did not affect the adaptation period and nutritional restriction in 1.4% of BW over 32 days improved feedlot performance, carcass characteristics and rumen morphometric of Nellore cattle. (AU)