Spent hen: Insights into pharmaceutical and commercial prospects

SUMMARY The global burden of poultry by-products management is exacerbated by the intensification of the poultry and egg industries worldwide. Spent hens, old female layer birds, which have completed their egg-laying cycle and lost their reproductive potential, are recognised as the most potent poultry by-products. However, the low consumer acceptance due to unfavourable physicochemical characteristics and the abundance of biological hazards in spent hen proteins consequently discourage their commercial processing. Therefore, the global poultry industry faces a substantial economic loss each year due to the higher disposal cost of the culled layer. In recent years, many strategies have been developed to improve the processing of spent hen proteins that manifest their potency in pharmaceutical and commercial applications. It is revealed that the hydrolysates of these by-products exert exclusive anti-ageing properties by ameliorating various ageing-related pathologies, such as hypertension, diabetes, liver diseases, skin diseases, and osteoarthritis, and modulating immune systems to combat ageing biomarkers, including oxidative stress and inflammation. In addition, several attempts succeeded in developing various commercial products, including soup and biomaterials, from the spent hen and its by-products. Despite that, even though the spent hen proteins have higher therapeutic and commercial potential, they received insufficient attention in protein-based research. Thus, this review aims to enlighten the prospects of spent hen proteins for encouraging their profitable utilisations in pharmaceuticals and other industries.