Effects of heat stress on performance, blood chemistry, and hypothalamic and pituitary mRNA expression in broiler chickens

作者：Ronique C. Beckford, Laura E. Ellestad, Monika Proszkowiec‐Weglarz, Linda Farley, Kristen Brady, R. Angel, Hsiao‐Ching Liu, Tom E. Porter · 发表于：Poultry Science · 年份：2020 · DOI：10.1016/j.psj.2020.09.052 · 被引用次数：95 · 研究领域：Animal Nutrition and Physiology、Effects of Environmental Stressors on Livestock、Meat and Animal Product Quality

This study was conducted to evaluate potential hormonal mechanisms associated with the stress response, thermoregulation, and metabolic changes of broiler chickens exposed to high environmental temperature. Nine hundred 1-day-old male broiler chicks (Ross 708) were placed in floor pens and raised to 24 d. At 24 d, chicks were randomly assigned to 1 of 2 treatments, heat stress (HS) or no HS, and allocated into battery cages in 8 batteries (10 birds per cage, 2 cages per battery). On day 31, blood was collected prior to HS and analyzed using an iSTAT analyzer. Half of the batteries were then moved into 2 rooms with an elevated ambient temperature (35°C) for 8 h. The remaining batteries stayed in the thermoneutral rooms with an ambient temperature of 22°C. Beginning at 5 h after the initiation of HS, blood was collected and analyzed using an iSTAT analyzer, birds were euthanized, and hypothalamus and pituitary samples were collected (16 birds per treatment), flash frozen, and stored at −80°C until RNA extraction. Reverse transcription-quantitative PCR was used to compare mRNA levels of key corticotropic and thyrotrophic genes in the hypothalamus and pituitary. Levels of mRNA for each target gene were normalized to PGK1 (pituitary) and GAPDH (hypothalamus) mRNA. Differences were determined using mixed model ANOVA. HS decreased (P < 0.05) feed intake, BW, bicarbonate, potassium, CO2, and triiodothyronine, while it increased mortality, glucose, pH, plasma thyroxine, and corticoste...