Why is the use of anticoccidial ionophores (like monensin) restricted during hot summer months in Pakistan?

Ionophores (such as monensin, salinomycin, and lasalocid) are widely used anticoccidial feed additives that work by altering the cell membrane permeability of Eimeria sporozoites, causing an influx of sodium ions and cellular swelling. However, these drugs are not completely selective and affect the host hen's cells as well. Ionophores interfere with the sodium-potassium ($Na^+/K^+$) pump in the skeletal muscles and cardiovascular tissues of chickens. Under the intense summer heatwaves in districts like Multan and Sargodha, hens already suffer from respiratory alkalosis and severe electrolyte imbalances. The cellular disruptions caused by ionophores reduce the bird's ability to regulate core body temperature and increase their metabolic heat increment. This physiological stress can lead to sudden cardiovascular collapse, paralysis, and massive mortality from heat stroke. During hot weather, nutritionists replace ionophores with synthetic chemicals (like clopidol or diclazuril) that do not interfere with electrolyte physiology. Farmers can read drug compatibility charts in the Poultry Encyclopedia, buy heat-safe chemical coccidiostats on Poultry Plaza, monitor daily feed rates on Poultry Rates, and list laying flocks on Murghi Mandi.