|STRONG, REBECCA - Purdue University|
|HESTER, PATRICIA - Purdue University|
|HU, JIAYING - Purdue University|
|Cheng, Heng Wei|
Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2015
Publication Date: 10/23/2015
Citation: Strong, R.A., Hester, P.Y., Eicher, S.D., Hu, J., Cheng, H. 2015. The effect of cooled perches on immunological parameters of caged White Leghorn hens during the hot summer months. PLoS One. 10(10): e0141215. doi:10.1371/journal.pone.0141215.
Interpretive Summary: Heat stress is a problem for the poultry industry in the United States, which causes a huge economic loss annually. Various means of providing supplemental cooling to hens in facilities are available, including evaporative cooling from either pads or fogging systems. Evaporative cooling efficiency can be seriously compromised by the development of an axial building’s temperature gradient as heat loss by hens raises the air temperature. In addition, fogging nozzles can generate too much moisture; water can drip leading to wet manure causing increased ammonia production and fly populations. This study was conducted in Indiana during the summer of 2013 to determine if providing a thermally cooled perch improves hen immunity during hot summer months. In this study, heterophil to lymphocyte ratio, a stress indicator, was reduced in hens from the thermally cooled perch group compared to control hens without thermal cooled perches. There were no treatment effects on the other measured physiological and immune parameters. These results indicated that the thermally cooled perch system used in this study prevented some of the heat stress reactions. However, the natural ambient temperatures of the 2013 summer in Indiana were not severe enough to evoke significantly physical and physiological changes. Further studies are needed to evaluate the effectiveness of thermally cooled perches on hen health under higher ambient temperatures. These results can be used by egg producers and scientists to develop management guidelines for improving hen welfare.
Technical Abstract: The objective of this study was to determine if thermally cooled perches improved hen immunity during the hot summer months. White Leghorn pullets at 16 weeks of age were randomly assigned to 18 cages of 3 banks at 9 hens per cage. Each bank was assigned to 1 of the 3 treatments up to 32 weeks of age: 1) thermally cooled perches (CP), 2) perches with ambient air (AP), and 3) cages without perches (NP). Hens were exposed to natural ambient temperatures from June through September 2013 in Indiana with a 4 h acute heat episode at 27.6 weeks of age. The packed cell volume, heterophil to lymphocyte (H/L) ratio, plasma concentrations of total IgY, and cytokines of interleukin (IL)-1ß, IL-6, and tumor necrosis factor-alpha were measured at both 27.6 and 32 weeks of age. The mRNA expressions of these cytokines, toll-like receptor-4, and inducible nitric oxide synthase were also examined in the spleen of 32 week-old hens. Except for H/L ratio, thermally cooled perches did not improve immunological indicators. These results indicated that the ambient temperatures of 2013 summer in Indiana (24°C, 17.1 to 33.1°C) was not high enough and the 4 h heat episode at 33.3°C (32 to 34.6°C) was insufficient in length to evoke severe heat stress in hens. However, CP hens had a lower H/L ratio than both AP hens and NP hens at 27.6 weeks of age (P < 0.01) and it was still lower compared to NP hens (P < 0.05) at 32 weeks of age. The lowered H/L ratio of CP hens suggested that they were able to cope with acute heat stress more effectively than NP hens. Further studies are needed to evaluate the effectiveness of thermally cooled perches on hen health under higher ambient temperatures.