Fortified single cell protein as an alternative protein source in dairy cattle: A comprehensive review

India, the world’s largest milk producer, contributes nearly 25% of global milk output, with production of 210.96 million tonnes in 2024-25. The dairy sector is central to India’s rural economy, supporting over eight crore farmers and contributing significantly to national GDP. Rising feed costs and protein shortages necessitate alternative, sustainable protein sources for dairy production. Single Cell Protein (SCP), derived from microorganisms such as bacteria, yeast, fungi and algae grown on agro-industrial wastes, has emerged as a viable option. SCP is rich in crude protein (45-80% DM), essential amino acids, vitamins and minerals. Produced mainly through fermentation, SCP can partially replace conventional protein sources like soybean meal and groundnut cake. Dietary inclusion of 5-25% SCP has been shown to improve nutrient digestibility, rumen efficiency, milk yield and milk composition. Fortified SCP further enhances antioxidant status, udder health and reproductive performance. However, challenges such as high production costs, compositional variability, nucleic acid content, palatability and regulatory issues limit its large-scale adoption. With suitable technological and economic interventions, SCP holds strong potential as a sustainable protein supplement for India’s dairy sector.