20 Replacing conventional protein sources and Flint Corn with dried distillers grains with solubles in finishing diets for beef cattle.

Abstract The increasing availability of dried distillers grains with solubles (DDGS) in Brazil and the limited research on its inclusion in feedlot diets, which typically use ground flint corn, soybean meal, and whole cottonseed as the main sources of energy and protein, highlight the need to investigate the replacement of these ingredients with DDGS. This study aimed to compare the performance (experiment 1) of Nellore bulls and the metabolism (experiment 2) of Angus × Nelore steers fed diets containing 0 or 40% DDGS (DM basis), fully replacing soybean meal and whole cottonseed and partially replacing ground flint corn. In experiment 1, 361 Nellore bulls (517 ± 36 kg) were allocated into 60 experimental pens for 39 days (30 pens per treatment), and dry matter intake (DMI), average daily gain (ADG), feed efficiency (G:F), and carcass characteristics were evaluated. In experiment 2, 16 Angus × Nelore steers fitted with ruminal cannulas (average body weight of 608 kg) were kept in individual pens for 21 days (8 animals per treatment), assessing ruminal parameters (short-chain fatty acids - SCFA, ammonia concentration, ruminal pH, and methane production) and apparent nutrient digestibility in the total tract. The experimental designs were a randomized block design, and data were analyzed using the MIXED procedure (SAS Inst., Inc., Cary, NC, 2009). No significant differences were observed between treatments for average daily gain (P = 0.3115) and dry matter intake (P = 0.6519), as well as for feed efficiency (P = 0.198). Hot carcass weight (P = 0.5376) and hot carcass yield (P = 0.3452) were also not influenced by the diets. The longissimus muscle area showed a tendency toward significance (P = 0.0706), while subcutaneous fat thickness was not affected by treatments (P = 0.4928) (Table 1). Regarding apparent digestibility, no significant differences were found for dry matter (P = 0.3849) and organic matter (P = 0.2247). and crude protein (P = 0.0567). However, digestibility tended to be greater in the DDGS diet for crude protein (P = 0.0567), was higher in the DDGS diet for neutral detergent fiber (P = 0.0259) and lower for non-fibrous carbohydrates (P = 0.0325). Total SCFA concentration (P = 0.914), the C2:C3 ratio, and ruminal pH (P = 0.8682) showed no significant differences. Methane production, expressed both in mol/kg/day and g/kg/day, also did not differ between treatments (P = 0.821 and P = 0.8265, respectively). In conclusion, DDGS can fully replace soybean meal and whole cottonseed and partially replace ground flint corn in feedlot diets without compromising animal performance.