|Mack, L -|
|Felver-Gant, J -|
|Cheng, Heng Wei|
Submitted to: Poultry Science
Publication Type: Abstract Only
Publication Acceptance Date: March 18, 2010
Publication Date: July 11, 2010
Citation: Mack, L.A., Felver-Gant, J.N., Dennis, R.L., Cheng, H. 2010. Effects of Heat Stress on Egg Production and Quality in Two Strains of Layers [abstract]. Poultry Science. 89:M311(E-Suppl. 1). Technical Abstract: Heat stress is a problem for both egg production and bird well-being. Given a stressor, genetic differences can alter the type and degree of birds’ responses and their adaptation. This study examined heat stress responses of two strains of White Leghorns: DeKalb XL (DXL), an individually-selected, commercial strain and a strain of kind, gentle birds (KGB) genetically-selected on high group productivity and survivability. Ninety 28wk-old birds (48 DXL, 42 KGB) were randomly paired, housed by strain and assigned to hot (H) or control (C) treatments for 14 days (mean: H= 32.6°F, C=24.3°F). Birds’ egg production (egg number, EN; egg weight, EW; shell thickness, ST; and percentage of broken eggs, PB), behavior and physical parameters (body weight, BW; ovary weight, OW; number of mature follicles, FN; and crop feed weight, CF) were measured. Compared to C birds, EN, EW, and ST were lower in H birds across both strains (P<0.05). In H birds but not in C birds, both EN and EW increased over time while ST decreased. The PB tended to be greatest in the H-DXL, intermediate in the C birds, and lowest in the H-KGB birds, but a significant difference was found between H-DXL and H-KGB only (P<0.5). Behaviorally, comparing treatments, H birds spent more time drinking and resting, and less time sitting (P<0.05) than C birds. Comparing strains, DXL birds rested more on day 1 (P<0.05) and tended to drink more on day 13 than KGB birds (P<0.1). C-KGB birds ate more frequently than C-DXL birds on days 6 and 11 (P<0.05) but no strain difference was evident in responding to heat stress (P>0.05). H-KGB birds tended to have lower CF weights than C-KGB birds at both week 1 and 2, while H-DXL birds tended to have higher CF weights than C-DXL birds at week 1 only (P<0.1). Body weight, day 14 OW and FN were all reduced in the H birds compared to relative controls (P<0.05). Although heat stress reduced production parameters in both strains of birds, genetic background shapes both the nature and intensity of the response.