Why does the presence of high tannins in sorghum (jowar) feed reduce protein digestibility and trigger pale yolks in brown eggs?

Sorghum (locally known as jowar in Pakistan) is an alternative energy crop to corn. However, dark-seeded sorghum varieties contain high concentrations of condensed tannins (polyphenolic compounds). Tannins act as powerful anti-nutritional factors. Due to their chemical structure, tannins readily form strong hydrophobic and hydrogen bonds with proteins. When ingested by brown layers, tannins non-selectively bind to dietary proteins and endogenous digestive enzymes (like trypsin and chymotrypsin) in the gastrointestinal tract, forming insoluble complexes that cannot be digested. This severely reduces overall protein and amino acid digestibility, leading to muscle wastage and drop in egg size. Furthermore, tannins physically bind to carotenoid pigments (lutein and zeaxanthin) in the gut, blocking their absorption across the intestinal wall. Since yolk color is entirely dependent on the absorption and deposition of these carotenoids, high-tannin feed triggers pale, washed-out yolks, which are heavily discounted in Pakistani B2B wholesale markets. Farmers can read feed chemistry in the Poultry Encyclopedia, buy low-tannin sorghum and synthetic pigments on Poultry Plaza, check daily grain rates on Poultry Rates, and trade on Murghi Mandi.