Total replacing soybean meal with extruded urea in supplements on the intake, ruminal, and metabolic parameters of beef cattle during the rainy and wet-dry transition seasons.

The objective was to evaluate supplement intake, ruminal parameters, and blood parameters of beef cattle supplemented with different protein sources (soybean meal or extruded urea- starea) during the rainy and wet-dry transition seasons. Four ruminally cannulae crossbred cattle were distributed in a completely randomized design in four paddocks Brachiaria brizantha cv. Marandu, with two paddocks per treatment, with three 30-d periods each season (rainy and wet-dry). The treatments were: (1) Concentrated supplement containing extruded urea (Starea) and (2) Concentrated supplement containing soybean meal. During the rainy season, the animals received 0.45% of BW in supplement per day. In the wet-dry transition period, the animals received 0.70% of BW of supplement per day. Animals fed soybean meal had greater supplement intake. The treatment with extruded urea supplement had rumen pH higher in the wet period. There was an interaction of treatment × hour for ammonia N for both seasons, where during the wet season, soybean meal at 6 h sampling had greater ammonia N compared with the other treatment, and during the wet-dry transition, soybean meal at 6 h and extruded urea supplement at 0 h had greater ammonia concentration. The total VFA was not affected by treatment independent of the season. The acetate: propionate ratio was lower with soybean meal supplement during the wet season. The total replacement is not recommended of true protein by non-protein nitrogen sources in supplements for beef cattle kept in Marandu-grass pastures during the rainy and wet-dry transition seasons.