Heat and Moisture Production of Molting Laying Hens

Abstract

<p>Heat and moisture production rates (HP, MP) of modern 68- to 75-week-old Hy-Line W- 36 laying hens during the molting stage were measured using large-scale indirect calorimeters that mimic commercial production settings. The HP and MP were measured continuously during acclimation, fasting, restricted feeding, and postmolt or normal periods. Total HP (THP) was partitioned into latent and sensible HP (LHP, SHP), which incorporated the influence of fecal moisture evaporation. THP during fasting (averaging 4.8 W/kg) and restricted feeding (averaging 6.0 W/kg) periods averaged 29 and 13% lower than that during postmolt period (averaging 6.8 W/kg). Correspondingly, LHP averaged 1.9 W/kg and 1.8 W/kg and was 31 and 34% lower than that during postmolt period, which averaged 2.7 W/kg. Likewise, SHP averaged 2.9 W/kg during fasting period and was 28% lower than during postmolt period, which averaged 4.1 W/kg. The average SHP between restricted feeding and postmolt periods were similar (4.2 vs. 4.1 W/kg, respectively). The respiratory quotient (RQ) averaged 0.71, 0.76, and 0.92 during fasting, restricted feeding, and postmolt periods, respectively. HP values during the light period were significantly higher (P<0.05) than those during the dark period. The daily mean and diurnal LHP as a percentage of THP were similar during fasting and postmolt periods and were comparatively 10% lower during restricted feeding period. The results of this study provide a new thermal load database for design of building ventilation systems for laying hens undergoing molting phase.</p>