Central regulation of drinking water in divergently selected high-water-efficient young broiler chickens: A minireview

Abstract

Poultry production is confronting real challenges, including a lofty projected high demand for animal proteins to feed the future, and the need to adapt to planetary boundaries (global warming) with limited natural resources (land, energy, water). Among the most challenging stressors to poultry production sustainability are heat stress (HS) and water uncertainty, that need extensive fundamental and applied research to identify effective strategies. In that regard, our group has recently developed a high-water-efficient broiler (meat-type) chicken line using water conversion ratio (WCR) as a phenotypic trait and defined the hypothalamic molecular mechanisms controlling drinking water under heat stress conditions. In response to the invitation from the Organizing Committee of the 13th International Symposium on Avian Endocrinology (ISAE 2024), the present review summarizes these data and closes the chapter by asking questions for future investigations. Data showed that HS exposure increased core body temperature (CBT) of both lines, with higher degree in HWE than in LWE counterparts. Despite this increase in CBT, HWE line drank less water but had superior performance with better feed conversion ratio (FCR) and WCR than LWE line. Molecular analyses showed that hypothalamic drinking-related neuropeptides (arginine vasopressin system, aquaporin system, renin, and angiotensin system) are affected in line- and/or environmental-dependent manner. Together, our research outcome indicates that the divergent selection for water efficiency could be an effective strategy to preserve water while maintaining optimal growth performance and could be applied to other poultry species and livestock.

Keywords: broilers; gene expression; hypothalamus; thirst; water efficiency.

FIGURE 1

Schematic representation and modulation of thirst regulation. Thirst, the desire and the urge of water drinking, is induced by cellular water depletion which affects blood volume, pression, and osmolarity. The brain detects these changes through baroreceptors and osmoreceptors and stimulates the release of AVP, which in turn induces water intake and activates RAAS system, and increases water reabsorption in the kidney (less water waste in urine) via AQP system. The secretion of Ang II induces vasoconstriction, activates AVP, and induces water intake. The aldosterone release from the adrenal gland reduces sodium secretion in urine. Ang II, angiotensin II; AQP, aquaporin; AVP, vasopressin; RAAS, renin angiotensin aldosterone system. The image is not for scale and it is developed using Biorender (Biorender.com).

FIGURE 2

Anticipatory and delayed neural circuits regulating thirst. The SFO‐MnPO‐OVLT axonal‐projection framework controls thirst‐ and drinking‐related behaviors and hormonal outputs. The SFO neurons projecting to the NTS control salt intake. Drinking water has two responses: a rapid anticipatory response that may depend on blood oxygen levels and/or water taste receptor that tracks water ingestion, and a delayed signal that monitors blood tonicity. AVP, vasopressin; MnPO, median preoptic nucleus; NTS, nucleus tractus solitarius; OVLT, organum vasculosum of lamina terminalis; PVH, paraventricular hypothalamus; SON, supraoptic nucleus. Figure was made using Biorender (Biorender.com).

FIGURE 3

Characteristics of HWE and LWE lines. Morphology (A), core body temperature (B), cumulative water intake (C), and cumulative feed intake (D). Core body temperature was determined using iButton thermologgers. BT, body temperature; FI, feed intake; HS, heat stress; HWE, high water efficient; LWE, low water efficient; TN, thermoneutral; WI, water intake. Figure was modified from.