This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. Received: JAccepted: OctoPublished: October 23, 2015

PLoS ONE 10(10):Įditor: Abderrezak Bouchama, King Abdullah International Medical Research Center, SAUDI ARABIA Further studies are needed to evaluate the effectiveness of thermally cooled perches on hen health under higher ambient temperatures.Ĭitation: Strong RA, Hester PY, Eicher SD, Hu J, Cheng H-W (2015) The Effect of Cooled Perches on Immunological Parameters of Caged White Leghorn Hens during the Hot Summer Months. The lowered H/L ratio of cooled perch hens may suggest that they were able to cope with acute heat stress more effectively than control hens.

However, cooled perch hens had a lower H/L ratio than both air perch hens and control hens at 27.6 week of age and it was still lower compared to control hens ( P < 0.05, respectively) at 32 week of age. These results indicated that the ambient temperature of 2013 summer in Indiana (24☌, 17.1 to 33.1☌) was not high enough and the 4 h heat episode at 33.3☌ (32 to 34.6☌) was insufficient in length to evoke severe heat stress in hens. Except for H/L ratio, thermally cooled perches did not significantly improve currently measured immunological indicators.

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. The packed cell volume, heterophil to lymphocyte (H/L) ratio, plasma concentrations of total IgG, and cytokines of interleukin-1β and interleukin-6, plus lipopolysaccharide-induced tumor necrosis factor-α factor were measured at both 27.6 and 32 week of age. Hens were exposed to natural ambient temperatures from June through September 2013 in Indiana with a 4 h acute heat episode at 27.6 week of age.

Each bank was assigned to 1 of the 3 treatments up to 32 week of age: 1) thermally cooled perches, 2) perches with ambient air, and 3) cages without perches. White Leghorn pullets at 16 week of age were randomly assigned to 18 cages of 3 banks at 9 hens per cage. The objective of this study was to determine if thermally cooled perches improve hen immunity during hot summer.

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