Blood acid/base balance in poultry: Dietary, environmental, and physiological determinants and emerging diagnostic opportunities

Acid/base balance is a central integrative process in poultry physiology, linking respiratory gas exchange, renal ion handling, skeletal mineral buffering, and cellular metabolism, with direct consequences for growth performance, skeletal integrity, eggshell quality, cardiopulmonary function, and survival. Although the mechanistic basis of acid/base regulation in birds has been well described for decades, direct assessment of blood acid/base status remains uncommon in commercial poultry production, where diet formulation targets and performance outcomes are often used as lagging and indirect proxies for physiological disruption. This review synthesizes classical and contemporary evidence describing the unique features of avian respiratory and renal physiology that govern blood pH, bicarbonate availability, electrolyte distribution, and calcium bioavailability. These physiological features explain why poultry are particularly sensitive to disturbances arising from dietary electrolyte composition, heat stress, ventilation, stocking density, and renal compromise. We highlight limitations of the dietary electrolyte balance concept as a surrogate for physiological status and demonstrate that both metabolic acidosis and alkalosis exert predictable but often under‑recognized effects on mineral metabolism, oxygen transport, and cardiovascular health. Central to this synthesis is the argument that blood acid/base biomarkers including pH, bicarbonate, base excess, electrolytes, strong ion difference, the anion gap, and others, provide a highly informative, integrative readout of nutritional adequacy, environmental stress, and renal function. The emergence of portable point‑of‑care blood analysers now enables rapid, on‑farm measurement of these variables, offering a practical pathway to move from anticipatory and formulation‑driven, to data-led physiology‑driven, decision‑making. Routine use of blood biomarker testing therefore represents a significant opportunity to improve diagnostic precision, nutritional management, and health and welfare outcomes in modern poultry systems.