Technical Note: HEAT AND MOISTURE PRODUCTION OF W‐36 LAYING HENS AT 24°C TO 27°C TEMPERATURE CONDITIONS

This study was conducted to quantify heat and moisture production (HMP) of W‐36 laying hens in their prime laying phase (27 to 33 weeks of age) using four large‐scale indirect animal calorimeters. Two experiments were conducted involving two groups of hens. The hens were exposed to conditions of 24°C to 27°C and concomitant relative humidity (RH) of 45% to 65% for six weeks. In each experiment, a total of 216 laying hens were used, with 54 hens housed in each of the four calorimeters at the cage stocking density of 435 cm2 hen‐1 (67 in.2 hen‐1) that was typical of industry practice. Total heat production (THP), room‐level latent heat production (LHP), and room‐level sensible heat production (SHP) were expressed as daily time‐weighted average (TWA), with an average of 16 h light and 8 h dark. The results showed that HMP was similar for the 24°C to 27°C temperature range. THP, LHP, and SHP, in W kg‐1 (mean ±SE) were, respectively, 6.1 ±0.3, 2.3 ±0.2, and 3.8 ±0.1 for the daily TWA; 6.5 ±0.3, 2.4 ±0.2, and 4.1 ±0.1 for the light period; and 5.4 ±0.3, 2.2 ±0.2, and 3.2 ±0.1 for the dark period. The HMP data contribute to the design and operation of ventilation systems in modern laying hen housing.