Selenium (Se) is an essential trace element for animals and humans, playing a crucial role in antioxidant defense, immune function, and reproductive health. The Se has significant potential in forage crops as it can enhance biomass productivity (primarily by improving photosynthetic efficiency), and, the nutritional quality traits of fodder. Additionally, the application of Se in forage crops can enhance its bioavailability to grazing animals, improving their health (by improving digestion and rumen function) and milk productivity. However, its presence in soils varies widely, affecting its availability in forage crops. Se deficiency in livestock is a global issue, leading to various health disorders, including white muscle disease, reproductive failure, and reduced growth performance. Research indicates that selenium acts as an antioxidant, and contributes positively to plant growth, especially when soil Se levels are managed appropriately. Additionally, selenium-rich materials can provide essential nutrients for forage crops, enhancing their overall nutrient profile. This chapter explores the potential of Se application in forage crops, including its sources, application methods, effects on plant growth and nutritive value, and their implications for animal and human health. Moreover, it also highlights challenges and future research directions in optimizing Se application in forage crops for boosting nutrition of milch animals.