| Summary: | We investigated the effect of different ambient temperatures and relative humidity (RH) with the same temperature-humidity indices (THI) on laying performance, egg quality, heterophil to lymphocyte ratio (H/L ratio), corticosterone (CORT) concentration in blood, yolk, and albumen, and plasma biochemical parameters of laying hens. Commercial hens (Hy-Line Brown; <i>n</i> = 120), aged 60 weeks, were allocated to two environmental chambers. Laying hens were subjected to either one of two thermal treatments—26 °C and 70% RH (T<sub>L</sub>H<sub>H</sub>75) or 30 °C and 30% RH (T<sub>H</sub>H<sub>L</sub>75) for 28 days—with the same THI of 75. Neither T<sub>L</sub>H<sub>H</sub>75 nor T<sub>H</sub>H<sub>L</sub>75 affected laying performance, including egg production, egg weight, egg mass, feed intake, and feed conversion ratio (<i>p</i> > 0.05). Plasma biochemical parameters such as total cholesterol, high-density lipoprotein cholesterol, triglycerides, calcium, magnesium, and phosphorus were not altered by the environmental treatments (<i>p</i> > 0.05). As for stress indicators, both environmental regimes failed to affect blood H/L ratio and CORT levels in plasma, yolk, and albumen (<i>p</i> > 0.05), although albumen CORT levels were elevated (<i>p</i> < 0.05) in T<sub>L</sub>H<sub>H</sub>75 group at day 7. Hence, our study suggests that laying hens performed and responded similarly when exposed to either T<sub>L</sub>H<sub>H</sub>75 or T<sub>H</sub>H<sub>L</sub>75 characterized by the same THI. These results can serve as a scientific basis for management decisions and handling laying hens under thermally challenging conditions.
|
|---|