The yield and physical-chemical properties of mammals’ milk depend on genetic, physiological and environmental factors. Owing to a valuable chemical composition and potentially health-promoting properties, mare’s and jennet’s milk has recently gained in popularity. The protein content in mare’s milk (1.5 ÷ 2.8 %) is higher than that in jennet’s milk (1.5 ÷ 1.8 %) and lower than that in cow’s milk (3.1 ÷ 3.8 %). Mare’s milk is recommended, inter alia, owing to its content of lactoferrin (9.9 ÷ 10.0 % of whey proteins), lysozyme (6.6 ÷ 6.9 % of whey proteins) and immunoglobulins (8.7 ÷ 20.9 % of whey proteins). The content of immune proteins in cow’s and jennet’s milk ranges, respectively, between: 10.1 ÷ 11.7 % and 10.9 ÷ 11.2 % in relation to the content of whey proteins; in cow’s milk lysozyme is found in trace amounts, whereas in jennet’s milk its content can be even as high as 20 %. Lactoferrin is the second antimicrobial component after lysozyme. Its highest amount is found in jennet’s milk (23.4 ÷ 25.1 % of whey proteins); next in mare’s milk (9.9 ÷ 10.0 % of whey proteins) and in cow’s milk (7.8 ÷ 8.4 % of whey proteins). The content of lactose in jennet’s, mare’s and cow’s milk is, respectively: 5.8 ÷ 7.4 %, 5.8 ÷ 7.0 % and 4.4 ÷ 4.9 %, while the content of fat is, respectively: 0.28 ÷ 1.82 %, 0.5 ÷ 2.0 % and 3.5 ÷ 4.0 %. Jennet’s milk is rich in vitamin C, but it has a lower content of vitamins A and E. Also, it is characterised by a higher content of vitamins D3 and B2 compared to cow’s milk and mare’s milk. Cow’s and jennet’s milk is characterised by a higher content of sodium, calcium and zinc compared to mare’s milk. In jennet’s milk there are  found the lowest amounts of potassium and copper and the highest content of iron. Cow’s milk is found to be the richest in copper and potassium. A valuable chemical composition of mare’s and jennet’s milk makes them interesting for technologists and dieticians.