Nutritive value of Urochloa decumbens Stapf R. D. Webster and Mimosa caesalpiniifolia Benth. and performance of cattle in monoculture and silvopastoral systems, in the Agreste region of Pernambuco.

This study evaluated the nutritive value of signalgrass (Urochloa decumbens Stapf R. D. Webster) and sabiá (Mimosa caesalpiniifolia Benth.), and animal performance in grass monoculture pastures and in silvopastoral system (SPS) in the early development stage, in the Agreste of Pernambuco. Four treatments were evaluated in a randomized block design with three replications: signalgrass + Eucalyptus spp.; signalgrass + sabiá; signalgrass monoculture and sabiá monoculture. Holstein × Zebu crossbred calves (170 ± 15 kg BW) were managed under continuous stocking with variable stocking rate (SR). The dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), and in vitro dry matter digestibility (IVDMD) of signalgrass and sabiá were assessed, as well as forage allowance (FA), stocking rate (SR), average daily weight gain (ADG) and weight gain per area (WGA) over eleven evaluation cycles (March 2019 to January 2020). Signalgrass had the highest DM contents in March 2019 and January 2020 (456 and 507 g kg-1, respectively), while for IVDMD the highest values ranged from 436 to 547 g kg-1 (April to August 2019). Sabiá presented the highest's IVDMD (311 and 381 g kg-1 DM) and DM content (385 and 416 g kg-1) and lowest CP (110 and 82 g kg-1 DM) and NDF (568 and 500 g kg-1 DM) in November 2019 and January 2020, respectively. FA and SR decreased throughout the evaluation cycles. ADG (0.38 kg animal-1 day-1) and WGA (17.89 kg ha-1 28 days-1) did not differ among treatments, with weight loss in the period of low water availability. In the early development stage of the trees, SPS does not affect the nutritive value of signalgrass, nor the animal performance.