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Differential Effects of Heat Stress in Three Strains of Laying Hens¹

D. J. Franco-Jimenez^*,2, S. E. Scheideler^*, R. J. Kittok^*, T. M. Brown-Brandl, L. R. Robeson^*, H. Taira^* and M. M. Beck^*,3,4

^* Department of Animal Science, University of Nebraska, Lincoln 68583; and USDA-US Meat Animal Research Center, Clay Center, NE 68933

Correspondence: ³ Corresponding author: mbeck{at}clemson.edu

Hy-Line Brown, W36, and W98 hens were housed for 2 wk at 22°C, exposed to 35°C heat stress (HS) for 2 wk, and had 2 wk of recovery at 22°C. Production parameters (egg production, feed intake, egg quality measures, and mortality), acid-base status (pH, pCO₂, HCO₃^–, pO₂), intestinal calcium uptake, and expression of hepatic heat shock protein-70 were measured. All production parameters except mortality were reduced by HS in all 3 strains. There were strain x temperature interactions for egg production, feed intake, shell thickness, specific gravity, and yolk weight, with the least severe reduction in W98 hens. The W36 hens were intermediate for egg production and feed intake, and the Brown and W36 hens were equivalent for shell thickness, specific gravity, and yolk weight. There were no interactions for egg, albumen, and shell weights, Haugh units, and intestinal calcium uptake, and all were reduced by HS. Blood pH and pCO₂ were reduced by HS, and hepatic heat shock protein-70 was increased, with no differences among strains. Mortality rates during HS were 16, 8, and 4% for the Brown, W98, and W36 hens, respectively, but were not subjected to statistical analysis. The results suggest a mechanism in the W98 bird that appears to confer an advantage during HS with regard to egg production.

Key Words: heat stress • laying hen • strain • production • heat shock

¹ Published as journal series 15053, Agricultural Research Division, University of Nebraska-Lincoln, NE 68583. Supported by USDA Regional Research Project NE-1022.

² Current address: California State Polytechnic University-Pomona, Animal and Veterinary Sciences, Pomona, CA 91768.

⁴ Current address: Department of Animal and Veterinary Sciences, Clemson University, Clemson, SC 29634.