What is the significance of the "critical temperature" lower and upper thresholds in commercial brown layer sheds?

The thermoneutral zone for commercial brown layers is between 18°C and 24°C, where flock productivity is maximized. Below the Lower Critical Temperature (LCT) of 15°C, the hen must consume extra feed and burn dietary energy to produce metabolic heat, which drastically degrades the Feed Conversion Ratio (FCR) and increases feed costs in cold regions like Rawalpindi during winter. Above the Upper Critical Temperature (UCT) of 28°C, the hen cannot lose body heat through normal radiation and begins evaporative panting. Panting induces respiratory alkalosis, depleting blood bicarbonate and causing paper-thin shells and a sharp drop in lay rate. Managing these thresholds using automated tunnel ventilation and heating systems is vital. Farmers can study environmental thermodynamics in the Poultry Encyclopedia, buy sensors and ventilation equipment on Poultry Plaza, track daily raw feed and egg prices on Poultry Rates, and trade high-yield flocks on Murghi Mandi.