Milk Fourier transform mid-infrared (FT-MIR) spectroscopy offers a rapid, cost-effective method to generate milk and animal phenotypes, with growing importance in both research and practical applications. It is already widely used for routine milk composition analysis and holds promise for broader implementation in management and breeding. This chapter focuses on the use of FT-MIR spectroscopy to quantify phenotypes in dairy cattle. It reviews its use for milk phenotype prediction, such as fatty acids, protein fractions, minerals and milk technological traits, and in animal phenotype prediction such as intake and energy balance, health and welfare, environment, fertility and heat stress. It also provides an overview of how FT-MIR can be utilised in global breeding programmes.