Recipient Organization
UNIVERSITY OF NEBRASKA
(N/A)
LINCOLN,NE 68583
Performing Department
ANIMAL SCIENCE
Non Technical Summary
Rises in environmental temperature is considered to be one of the most serious problems for poultry operations. A recent estimate of annual economic losses to the poultry industry because of heat stress related mortality and production decreases is $125 to $165 million. The deaths, in 1995, of layers in Iowa during a 2-wk heat wave amounted to ~$9 million in losses. The purpose of this study is to investigate genomic effects of heat stress on physiological variables differentially affected in different strains of hens.
Animal Health Component
20%
Research Effort Categories
Basic
80%
Applied
20%
Developmental
(N/A)
Goals / Objectives
To determine, using appropriate microarrays, gene expression profiles of specific elements of the steroidogenic pathway in three varieties of laying hens
Project Methods
This study will be carried out in the Animal Science Physiology Laboratories at the University of Nebraska-Lincoln. Experimental birds (Hy-Line W36, W98 and Browns) will be obtained from sources in Nebraska and Iowa; feed will be mixed at the UNL ARDC, Mead, NE. Hens will be housed in layer cages. All birds will be housed at normal stocking densities in thermally neutral environments (21-24C or 70-75F, ~50% relative humidity (RH)); samples from birds under these conditions will be the controls. All heat stress applications will be conducted in the environmental chambers in the Animal Science Department, where birds will be exposed to thermal challenges for 24h in initial experiments; subsequent challenges will last longer, increasing in increments of 24h each. Heat stress temperatures will be 35C, 50% RH, for Hy-Line white birds (W36, W98); and 31C, 50% RH for Hy-Line Browns. Body temperature and respiratory gas data will be collected continually on all birds during
the heat stress episodes. The following samples will be collected on all birds, both control and experimental: blood samples for hormone profiles (estrogen, progesterone, LH); oviduct and ovary for genomics analyses. In the case of chronic heat stress experiments, egg production and feed intake data will be collected from females. The hormone samples will be analyzed by Radioimmunoassay and histomorphometric methods, respectively, and will serve as additional controls to substantiate the effects of heat stress and to add to the base of data for these birds. For gene expression analyses, tissues (oviduct, ovary) will be obtained and processed for total RNA. Changes in gene expression will be determined using oligo-DNA microarrays obtained from the Delaware Chick EST Project, University of Delaware (Cogburn et al., 2003). Microarrays pco1c, pgr1c, and pgr1n, will be considered and the most appropriate used following consultation with Dr. Cogburn. Following microarray analysis, scanned
data will be analyzed and fold changes of gene expression determined (Watanabe et al., 2002). It is likely that, initially, samples from several birds within each group (treatment and control) will be pooled (B. White, personal communication) in order to minimize cost and enhance available RNA.