Thermoregulation in chicken chicks facing heat stress: water restriction and endotoxin (LPS) challenges

• Grant number: 22/00233-4
• Support Opportunities: Regular Research Grants
• Start date: June 01, 2022
• End date: July 31, 2024
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Production
• Principal Investigator: Kênia Cardoso Bícego
• Grantee: Kênia Cardoso Bícego
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil
• Associated scholarship(s): 24/06947-4 - Training in physiological responses and performance of broiler chicks facing heat stress, BP.TT; 23/09443-4 - Technical training on physiological responses and performance of broiler chicks facing heat stress, BP.TT; 22/10554-2 - Thermoregulation in chicken chicks facing heat stress: water restriction and endotoxin (LPS) challenges, BP.TT

Abstract

Heat exposure in the first week of life in precocious birds has been shown to be a more intense stress than exposure to cold. Furthermore, it is known that dehydration inhibits evaporative heat loss responses leading to hyperthermia, and that immunological challenge, depending on the intensity of the stimulus, leads to fever (increased metabolic demand) or regulated hypothermia (conservation of energy). In this context, this study will investigate the thermoregulatory responses and their neural control in broiler chicks facing heat stress under different conditions, such as complete hydration, water restriction and immune challenge. Three objectives will be addressed: 1) Considering the effect of fluid restriction as an inhibitor of panting, the neural regulation of the integration between thermoregulation and osmoregulation during exposure to heat will be investigated. To this end, body temperature (Tb), lung ventilation (VE), O2 consumption (VO2) and sensitive skin heat loss index (HLI) will be measured during heat exposure in one-week-old chicks, hydrated and with water restriction, after inhibition of the anterior hypothalamus with the glutamatergic antagonist AP5 or after lesion to hypothalamic GABAergic neurons with GAT1-Saporin. 2) Considering the high energy demand involved in the inflammatory response to a pathogen, the neural regulation of the integration of thermoregulatory responses in the face of heat and an immunological challenge will be investigated. In this case, Tc, VE, VO2 and HLI will be measured during heat exposure in one-week-old chicks, hydrated, and treated with lipopolysaccharide (LPS; endotoxin) after inhibition of the anterior hypothalamus with AP5 or after lesion to hypothalamic gabaergic neurons with GAT1-Saporin. 3) The zootechnical performance of the chicks associated with the manipulations in the previous objectives will be evaluated. To this end, the average gain in body mass/day, average feed and water intakes and feed efficiency in the first week of life will be determined. (AU)