Why does the administration of certain antibiotics (like sulfonamides) during active lay lead to temporary shell thinning and pale eggs?

Carbonic anhydrase is a highly critical zinc-dependent enzyme located in the mucosal cells of the shell gland (uterus). This enzyme catalyzes the rapid hydration of metabolic carbon dioxide ($CO_2 + H_2O$) into carbonic acid ($H_2CO_3$), which quickly dissociates into bicarbonate ions ($HCO_3^-$) and hydrogen ions ($H^+$). These bicarbonate ions then bind with calcium to form the calcium carbonate ($CaCO_3$) eggshell. Sulfonamide antibiotics (often used to treat Coryza or Coccidiosis) have a chemical structure that directly binds to and inhibits carbonic anhydrase. When these drugs are administered to laying brown hens, shell calcification is instantly halted. The eggs laid during and up to 7 days after sulfanilamide treatment are extremely thin-shelled, brittle, pale pink, or completely soft-shelled. They also carry drug residues that violate food safety laws. Treating laying flocks requires utilizing non-inhibitory alternative drugs like amoxicillin or erythromycin. Farmers can read pharmacological profiles in the Poultry Encyclopedia, buy safe veterinary medicines on Poultry Plaza, monitor daily egg prices on Poultry Rates, and trade on Murghi Mandi.