**2. Dairy milk bioactive components and their role on health and diseases**

### **2.1 Bovine milk**

Bovine milk as whole milk and its products are serving an easy way of achieving good nutrition. Bovine milk contains the nutrients needed for growth and development of the calf and is a resource of lipids, proteins, amino acids, vitamins, and minerals. The milk is also blessed with many substances like hormones, growth factors, immunoglobulins, peptides, cytokines, polyamines, bioactive peptides, and many enzymes that play different roles in our body [4]. Milk composition has dynamic properties and its composition varies depending on lactation, diet, age, breed, energy balance, and udder health. Colostrum is very different from milk, but the most important difference is the concentration of milk protein. It will be twice in colostrum compared with milk in late lactation. Lipids in bovine milk are suspended or emulsified in the form of fat globules covered with membranes. Lipids are mainly composed of different types of fatty acids having different fraction. Milk contains about 32 g of protein per liter. Milk protein is a good source of essential amino acids. In addition, milk contains various biologically active proteins, ranging from antimicrobial drugs and ending with nutritionally enriched proteins, as well as growth factors, hormones, enzymes, antibodies, and immune-stimulants. Nitrogen in milk is distributed in casein, serum, and nonprotein nitrogen. The content of casein in milk is about 80% of milk protein. Whey protein is a globular protein that is more soluble in water than casein. The main components are β-lacto globulin, α-lactalbumin, bovine serum albumin, and immunoglobulin. Milk also contains many minerals, vitamins, and antioxidants. Antioxidants prevent the oxidation of milk and also provide protection to cells which involve in milk production and to udder also. The most important antioxidants in milk are mineral selenium and vitamins E and A [5]. However, cow milk (CM) differs from buffalo milk (BM) composition of different milk bioactive components. Buffalo milk has lower cholesterol but more calories and fat compared with cow's milk. Cow milk has higher cholesterol level than BM, but higher fat contents are present in BM with higher calorie percentage. Buffalo milk has a higher content of fat, lactose, casein, whey proteins, and minerals than cow milk. All of the casein in buffalo milk is present in the micellar form, while in the CM, only 90–95% of the casein is in the micellar state and the rest is present in serum phase. The calcium content is higher in BM

than in milk from cow, and it contains more colloidal calcium and phosphorus. The BM is richer in fat than milk from cattle, and absence of b-carotene in BM, which is present in CM, is another notable characteristic [6].
