Productive, metabolic and economic responses of Nellore young bulls fed diets with different non-protein nitrogen source combinations

Abstract Nutrition is a key determinant of performance, carcass traits, and production efficiency in beef cattle. In this context, feed additives have emerged as a promising strategy to enhance nutrient utilization and reduce production costs. We aimed to evaluate the effects of replacing urea with a product extruded urea enriched with essential oils (NFeed ® ) on nutrient intake, performance, blood parameters, and feed cost in feedlot-finished Nellore young bulls. Twenty-four non-castrated animals with an average initial body weight of 394.6 ± 53 kg were randomly assigned in a completely randomized design, following the treatments considering different combinations of NPN source in diet: 0% NFeed (100% of non-protein nitrogen from urea), 50% NFeed (50% of non-protein nitrogen from urea and 50% of non-protein nitrogen from NFeed), 75% NFeed (25% of non-protein nitrogen from urea and 75% of non-protein nitrogen from NFeed) and 100% NFeed (100% of non-protein nitrogen from NFeed). Final body weight, total weight gain, and average daily gain had a linear response, with the highest values in the 100% NFeed treatment. Feed efficiency and feed conversion exhibited linear effects, with the 100% NFeed diet resulting in the greatest feed efficiency and the lowest feed conversion. A quadratic effect was observed for plasma urea, and gamma-glutamyl transferase levels. The replacement of conventional urea with extruded urea enriched with essential oils (NFeed) represents a viable nutritional strategy for finishing beef cattle in feedlot systems. Increasing levels of NFeed linearly improved animal performance while maintaining similar feed intake, increasing feed efficiency reducing feed conversion, and the cost per kilogram of body weight gain. Thus, we recommend a partial replacement of urea by NFeed as a non-protein source in beef cattle feedlot.