Effect of cooled perches on the efficacy of an induced molt in White Leghorn laying hens exposed to cyclic heat

Authors: HU, JIAYING - Purdue University; HESTER, PATRICIA - Purdue University; XIONG, YIJIE - University Of Illinois; GATES, RICHARD - University Of Illinois; MAKAGON, MAJA - Purdue University; Cheng, Heng-Wei

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2019
Publication Date: 12/11/2019
Citation: Hu, J., Hester, P.Y., Xiong, Y., Gates, R.S., Makagon, M.M., Cheng, H. 2019. Effect of cooled perches on the efficacy of an induced molt in White Leghorn laying hens exposed to cyclic heat. Poultry Science. https://doi.org/10.3382/ps/pez317.
DOI: https://doi.org/10.3382/ps/pez317

Interpretive Summary: Induced molt is a routine management practice used to rejuvenate the reproductive system of laying hens for extending their productive life. However, molting can be stressful; and its detrimental effects could become worse if induced molting is conducted during hot summers. In addition, each of the cooling methods currently applied in the egg industry, such as evaporative cooling, has certain disadvantages. The objective of this study was to evaluate the effect of water-chilled perches on hen production and physiological responses to induced molt during elevated temperatures (cyclic heating episodes at 21-32 oC from 0600 to 1800h daily). Chilled water (10 oC) was circulated through the cooling perches during the heat episodes. The results showed that the cooled perch system could be an effective alternative cooling method for caged laying hens, especially during induced molting conducted under elevated temperatures. Hens which had access to the cooled perches had a reduced stress response and increased egg production post-molt. These results can be used by egg producers to develop management strategies for improving hen health and welfare during induced molting.

Technical Abstract: This study examined the effect of water-chilled perches on hen production and physiological responses to induced molt during elevated temperatures. White Leghorns at 82 wk of age were assigned to 36 8-bird cages of 6 banks. Each bank was assigned to 1 of 3 treatments: cooled metal perches (CMP), uncooled metal perches (UMP), and no perches (NP). The hens were subjected to a 28 d non-fasted molting regimen starting at 85 wk of age. Cyclic heat of 21-32 oC (0600 to 1800h) was applied daily during the molting period. After molt, the hens were returned to a layer diet and housed under thermoneutral conditions. Two birds per cage were monitored for BW change during molt. Egg production was recorded daily. Feed utilization was measured during molt at 86 and 88 wk of age. Egg weight and eggshell traits were examined at 84 wk of age pre-molt and at 92, 96, and 104 wk of age post-molt. Rectal temperature and blood samples were collected from two birds per cage at the end of molt. Plumage condition was examined at 22 wk post-molt. Compared to NP and UMP hens, CMP hens had higher feed usage, greater BW loss, and lower heterophil/lymphocyte ratios (P < 0.05) without differences in the concentrations of thyroid hormones or corticosterone at the end of molt. CMP hens also had higher egg production beginning from 98 wk of age compared to NP hens and at some wk-time points compared to UMP hens (P treatment*age < 0.0001). In addition, CMP hens had higher rectal temperature than NP hens but not UMP hens at the end of molt. Moreover, CMP hens had better breast feather scores than UMP hens but worse vent plumage (P = 0.05) than both NP and UMP hens. These results indicate that the provision of cooled perches enhances hen ability to adapt to potent stressors, such as induced molt plus heat exposure, resulting in improved post-molt egg production.