411 Evaluating feeding protocols for optimal performance and efficiency in large beef cattle feedyard systems.

Abstract The number of diets and the duration of feeding phases may play a critical role in balancing physiological requirements and logistics within a large beef cattle feedyard system. To investigate this, we conducted a large pen trial study to assess the feasibility and performance outcomes of various feeding management protocols, focusing on the number of diets and the timing of feeding phases. A total of 2,757 24-month-old Nellore bulls [367.5 ± 21.7 kg of body weight (BW; mean ± SD)] were assigned to 52 open dry lot pens (n=55/pen; 13 pens/treatment) in a complete block design (8 blocks set by initial BW) with ad libitum access to feed and water. The treatments consisted of 4 feeding protocols: 1) CONV: 10d of adaptation + 3d of transition + 14d of growing + 4d of transition + 91d of finishing; 2) BLEND: 10d of adaptation + 14d of transition (50% adaptation + 50% finishing) + 98d of finishing; 3) PROLONGED: 10d of adaptation + 3d of transition + 35d of growing + 4d of transition + 70d of finishing; and 4) GROW/FIN: 0d of adaptation + 24d of growing + 4d of transition + 94d of finishing. Diets were formulated to provide nutrients for an ADG of at least 1.5 kg, according to the LRNS. Dry matter intake was evaluated in a pen approach (considering 1-2% of feed refusals) as well as BW and all derivations index created by combining these variables. Initial carcass weight (used in the carcass gain and carcass feed conversion), was estimated by considering 50% of dressing. All statistical analyses were performed using SAS version 9.4 (SAS Institute Inc.) considering pen as experimental unit. No differences were detected on performance outcomes. However, although some few differences have been observed on DMI during adaptation and growing phases, the final average DMI was not different among treatments. No effects were observed on carcass parameters among treatments. In conclusion, considering both performance and intake, all feeding protocols yielded similar results. Notwithstanding, such strategies should be carefully evaluated in the context of large beef cattle feedlot operations, with particular attention to the associated diet formulation/feeding management as well as logistics costs.