de sombra en el corral de engorda en la respuesta productiva de toretes en finalización de la época fresca y seca

to determine the effect of shade in feedlot pen on growth performance response of finishing bulls during the cool and dry season, a 63 days feedlot performance experiment was conducted from january to march of 2003. sixty six brahman crossed bull calves (males, bw = 370,14 ± 4,28 kg), were used in a complete block randomized experiment design. the animals were blocked by initial weight, and placed in ground pens (6 x 12 m), the treatments consisted in: a) pens without shade (control); or b) pens fitted with roof that provides 3 m2 of shade by animal (shade treatment). bulls were fed with 14:86 forage:concentrate diet containing cp 14 % and nem 1,85 mcal/kg. mean temperature was 22,4 °c and total raining water was 14,2 mm. shade increased (p < 0,01) 4 % final weight (462 vs 482 kg), and 16 % average daily gain (1,50 vs 1,74 kg/day). dry matter intake was not affected (p = 0,58) by treatments (10,41 vs 10,14 kg/day). feed conversion was improved (p < 0,01) by use of shade (6,94 vs. 5,84). carcass weight was increased (p < 0,01) 5,7 % by shade inside of pen (294,10 vs 310,95 kg). carcass dressing was not affected (p = 0,29) by treatments (64,5 vs. 63,9 %). nem obtained from the diet was improved (p = 0,02) by shade (1,866 vs 2,127 mcal/kg). observed/expected nem ratio was 14 % higher (p = 0,02) in shade treatment (1,01 vs 1,15). it is concluded, that the use of shade inside of feedlot pen improves near of 14 % the growth performance response of finishing bulls during the dry-cool season in the northwest of mexico