PSIX-7 Effect of season on feedlot performance of shade-protected finishing bull in a hot weather.

摘要

To determine the influence of season on feedlot performance of shade-protected finishing-bulls in a hot weather data from closeout of all lots of bulls-sales during 2017 in a commercial feedlot yard were use it. The feedlot yard placed in the Northwest of Mexico (24° 55’ N, 107° 33’ W and 72 m omsl), with a hot very dry weather. Data set involved 3 843 bulls (337.6 ± 26.72 kg initial wt.) predominant genotype was Brahman and its crosses with Bos taurus. Corral grouped by season of sales constituted the treatments: 1) Spring (n = 11); 2) Summer (n = 13); 3) Autumn (n = 12); and 4) Winter (n = 14). All corrals had similar dimensions (29 m wide x 37.7 m bottom), fitted with central ceiling (metal sheet built) that provide 3.5 mP = 0.02) season was summer (31.3 °C; THI 82.9), and the lower mean temperature was during winter (21.8 °C; THI 68.1). Air relative humidity was similar (P > 0.10) between summer and autumn (66.7 and 67.2%), then dropped (P < 0.01) during winter to 57.9%, spring RH was equal to all other seasons (P > 0.10). Winter ADG was higher (P = 0.05) than observed in summer and autumn with means of 1.47, 1.37, and 1.32 kg, respectively. DMI was similar across seasons (P = 0.38). Gain:feed ratio was similar (P > 0.10) during winter and spring (0.171 and 0.172), respectively, summer and autumn shown lower values (P = 0.05) than observed in winter and spring with means of 0.164 and 0.163 kg/kg. Results indicates that in the hot areas of Mexican Northwest the weather during autumn remain affected feedlot performance of finishing bulls as is during summer