Biological responses of hair sheep to a permanent shade during a short heat stress exposure in an arid region

Abstract

Abstract Summer heat stress (HS) in warm climates decreases feedlot performance and, in extreme cases, causes death in fattening lambs. A traditional strategy to mitigate effects of HS has been the installation of galvanized sheet metal shades that partially or totally cover the corrals; however, the impact of total shading on thermoregulation and growth in hair lambs has been little studied. Twenty Dorper × Pelibuey ewe lambs were assigned to two treatments (n = 10; non-shaded vs. shaded) for two weeks to evaluate the effects of providing total shading with galvanized sheet metal in the fattening corral on physiological variables, blood analyte concentrations and growth performance under HS conditions in an arid region. Rectal temperature and respiratory rate in shaded ewe lambs were higher at 0600 h and lower at 1200 and 1800 h compared to non-shaded ewe lambs. Shaded ewe lambs had lower serum levels of glucose, cholesterol, triglycerides, K+ and Cl−, but higher serum urea levels, compared to non-shaded ewe lambs. Additionally, most of the mean values of hematological variables were higher in shaded ewe lambs versus non-shaded. Shaded ewe lambs had higher feed intake but similar growth rate and water intake than its counterpart. In conclusion, under summer HS conditions in an arid region, the thermoregulatory capacity of hair ewe lambs is improved during the daytime but compromised in the nighttime by completely shading the feedlots with galvanized sheet metal. Additionally, the lack of protection against solar radiation negatively affected feed intake and energy metabolism.