Thermal comfort and performance of feedlot lambs finished in two climatic conditions.

• Performance – Lambs finished in the cold season were more efficient in the use of food. • Thermal comfort – The hot season provided conditions less suitable for finishing lambs.. • Behavior – The cold season allows better behavior of the physiological variables of the lambs. The aim of this study was to evaluate the thermal comfort, performance, and behavior of feedlot lambs finished in two climatic conditions. Twenty castrated Texel lambs at an average age of 75 days were used in the experiment. Diets consisted of corn silage as the roughage component plus concentrate, with roughage-to-concentrate ratios of 50:50 and 50.5:49.5 for the higher and lower heat conditions, respectively. Higher respiratory frequencies and temperatures in the eye region were observed in lambs finished in the higher temperature, whereas rectal temperature did not differ between the climatic conditions. Lambs finished in the higher and lower heat conditions experienced 15 and four days under heat stress, respectively, which correspond to 27.7 and 6.5% of the feedlot period. The group finished in the higher temperature conditions remained on average six hours per day under heat stress, whose peak occurred at 14h30 to 16h30. Dry matter intake relative to body weight and to metabolic weight did not differ between the climatic conditions. Lambs finished in the cold season were more efficient in using the feed based on their residual feed intake and feed and rumination efficiencies. Climatic conditions affected the performance and behavior of the lambs as a result of thermal discomfort. [ABSTRACT FROM AUTHOR]