Effects of genetic group x ambient temperature interactions on performance and physiological responses of Naked-neck chickens and their F1 crosses with Lohmann White and New Hampshire laying hens

Abstract

The objective of this study was to evaluate the effects of genotype x temperature interactions on hormonal heat stress indicators and performance traits. Two-hundred forty female one-day-old chicks were randomly assigned to a completely randomized design in a 5×2 factorial arrangement with 5 genotypes (Naked-neck, Na, from Ethiopia; New Hampshire, NH; Lohmann White, LW and F1 crosses of Na with NH and LW) and 2 ambient temperatures (thermo-neutral, 18-20°C; heat stress, 30-32°C). Blood samples were taken from 12 randomly selected birds per genotype and ambient temperature at 22, 38, 51 and 65 weeks of age. Levels of corticosterone (CS) and 3,5,3'-triiodothyronine (T3) were determined in blood plasma. Heat stress effects on egg production traits were most severe in LW and NH, least severe in Na and Na × LW, intermediate in Na × NH. Plasma T 3 level was significantly reduced by 27.9% in heat stressed genotypes. Plasma CS increased by 12.6% in heat exposed genotypes. However, inconsistent responses of CS and T3 levels were observed at different ages. The Na and their F1 crosses demonstrated relatively better thermotolerance than LW and NH hens. Levels of plasma T3 hormone might be considered as indicator of long-term heat stress in hens.