Resumen

BARAJAS CRUZ, Rubén et al. Effect of shade on feedlot pen on growth performance of finishing bulls during the dry-cool season. Zootecnia Trop. [online]. 2010, vol.28, n.3, pp.375-381. ISSN 0798-7269.

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

Palabras clave : shade; growth performance; finishing bulls.