Laying hen responses to acute heat stress and carbon dioxide supplementation: I. Blood gas changes and plasma lactate accumulation

Exposure to heat stress lowered partial pressure of arterial blood carbon dioxide (paCO₂), arterial blood bicarbonate ion (HCO^-₃), but increased arterial blood pH (pHa) and plasma lactate (LA). Increasing ambient carbon dioxide (CO₂) to 1.5% increased paCO₂ from hypocapnic levels to normocapnic levels, raised HCO₃^- lowered pHa and plasma LA to pre-heat stress levels. Following CO₂ treatment, respiratory alkalosis conditions returned. It was evident in this study that increasing ambient chamber CO₂ to 1.5% was effective in ameliorating acid-base disturbances and reducing elevated levels of plasma LA which normally develops when laying hens are subjected to an acute heat stress exposure.