PS4-20. High Inclusion of Fiber-separated DDGS Impairs Finishing Performance and Carcass Weight of Feedlot Nellore Bulls.

Abstract Distillers dried grains with solubles (DDGS) are widely included in feedlot diets as sources of protein, fiber, and energy; however, performance responses in Bos indicus cattle finished under high-concentrate systems remain inconsistent. This study evaluated the effects of increasing inclusion levels of DDGS plus fiber on finishing performance and carcass characteristics of Nellore bulls. A total of 236 bulls (initial BW = 383.53 ± 40.35 kg) were assigned to a randomized complete block design according to initial body weight (4 or 5 bulls per pen; 18 pens per treatment). Treatments consisted of: 1) a control diet without DDGS and containing 10% whole cottonseed (DM basis); 2) 20% DDGS (DM basis); and 3) 40% DDGS (DM basis). Diets contained 12% sugarcane bagasse, ground flint corn (74.5 to 46% of DM, depending on DDGS inclusion), DDGS (0, 20, or 40% of DM), urea (1.5 to 0.5% of DM), and a mineral and vitamins premix (2% of DM). Diets were formulated to support 1.5 kg/d of average daily gain according to NASEM (2016). The experimental period consisted of 22 d of adaptation followed by 103 d on finishing diets. Cattle were fed twice daily, and orts were collected twice weekly to determine dry matter intake (DMI). Feed and ort samples were dried at 105 °C for 24 h to determine DM concentration. Pen was considered the experimental unit for performance variables. Average daily gain (ADG) and feed efficiency (G:F) were calculated using pen means. At the end of the feeding period, cattle were weighed after 16 h of feed and water withdrawal to determine final shrunk body weight (FSBW). Following slaughter, hot carcass weight (HCW) and dressing percentage (DP) were recorded. Data were analyzed using the MIXED procedure of SAS. Least squares means are reported; significance was declared at P ≤ 0.05 and tendencies at 0.05 < P ≤ 0.10. Dry matter intake decreased linearly (P < 0.001) as DDGS inclusion increased, with bulls fed 40% DDGS consuming 1.08 kg/d less (−10.53%) than control animals. Adjusted ADG also decreased linearly (P < 0.001), with a reduction of 0.219 kg/d (−12.98%) at the highest inclusion level. Final BW and adjusted final BW decreased by 22.71 kg (−3.80%) and 26.11 kg (−4.35%), respectively, at 40% DDGS inclusion. Feed efficiency (G:F) was not affected (P = 0.62). Hot carcass weight decreased linearly (P < 0.001), with a reduction of 14.66 kg at 40% DDGS inclusion, whereas dressing percentage was not affected (P = 0.73). In conclusion, increasing inclusion of DDGS plus fiber up to 40% of dietary DM reduced finishing performance and hot carcass weight of Nellore bulls without improving feed efficiency.