Milk composition is affected by feed intake and physiological status of animals. Physiological status, in turn, is affected by environment. Milk composition and quality are important characteristics that determine the nutritive value and consumer acceptability. Three studies were conducted to investigate relationship of lactation stage and body condition with milk yield and composition with special reference to fatty acids in crossbred dairy cows and buffaloes (Bubalus bubalis) under tropical conditions. Nili-Ravi dairy buffaloes produce milk, with the highest concentration of C18:1 cis-9. Two HCFA (C12:0 and C14:0) were associated with higher body condition. Buffaloes with moderate body condition yielded milk containing healthier fatty acids. Concentrations of unsaturated fatty acids were higher in earlier weeks and declined during mid lactation. With advancement of lactation the proportion of both de novo fatty acids and poly-unsaturated fatty acids increased. C12:0, and C14:0 increased with advancing lactation and the cows in early lactation yielded milk containing healthier fatty acids.