The objective was to evaluate the effect of the feeding system on rumen papillae (RP) development and the animal welfare. The feeding systems used were: Intensive Silvopastoril (SPI) with grazing leukaena and Tanzania and African star grasses; Feedlot system (FLT) with a diet based on 70% of concentrate and 30% of corn stover. Eighty bulls of 2 breeding groups Brahman×Charolais (Bh×Ch) and Brahman×Brown Swiss (Bh×Ps) randomly distributed at both systems were used. The study lasted 195 d. Blood samples were taken at 0, 71, 132, and 195 d. Initial animal’s body weight was 195 kg. Animals were killed at 450kg body weight. Tissue samples of rumen were taken during slaughter of animals. Evaluated variables were length and width of RP using a Vernier caliper. The concentration of Cu, Zn and Mn in blood serum was measured by atomic absorption spectrophotometry. Data were analyzed with a completely randomized design with factorial arrangement 2 × 2. Measures repeated in time and 0d as a co-variable for the blood serum enzymatic cofactors concentration (SEC) were used. SPI favored (P < 0.01) RP development, with values of 1.16 ± 0.05 and 1.11 ± 0.05; 0.38 ± 0.03 and 0.36 ± 0.03 cm in length and width of RP of Bh×Ch and Bh×Ps respectively (Table 1). There were a decrease (P < 0.01) in Cu, Mn and Zn concentration for sampling day, with lowest values at 132d, due to a possible caloric stress for environmental high temperature and relative humidity. There was effect of system for SEC (P < 0.05), with increase for Cu and Mn but decrease of Zn in SPI. We concluded that SPI allowed to a better RP development by the quality of the fiber consumed in the diet, no matter the breed group, and a larger serum concentration of Cu and Mn, although with a significant reduction of Zn concentration. Table 1. Length and width of RP¹ and SEC of bulls fattened under two feeding systems

Variable	FLT	SPI
RP length (Bh×Ch)	0.63 ± 0.09b	1.16 ± 0.05a
RP length (Bh×Ps)	0.76 ± 0.07b	1.11 ± 0.05a
RP width (Bh×Ch)	0.20 ± 0.05b	0.38 ± 0.03a
RP width (Bh×Ps)	0.22 ± 0.04b	0.36 ± 0.03a
Cu (mg/L)	0.108 ± 0.004b	0.124 ± 0.004a
Mn (mg/L)	0.379 ± 0.010b	0.424 ± 0.011a
Zn (mg/L)	0.533 ± 0.030a	0.406 ± 0.032b

¹Length and width of RP are expressed in cm.