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Protein content in cow milk (with over 20 proteins, and peptides may also occur as a result of enzymatic hydrolysis) ranges from 2.5% to 4.2% and is about 1.5-2 times higher than in human milk. Its most important allergens are considered to be β-lactoglobulin (absent in human milk) and αs1-casein. The most similar in composition to human milk is horse and donkey milk. It contains considerably more whey proteins (35-50%) than cow milk (about 20%), and the concentration of the most allergenic casein fraction αs1 is 1.5-2.5 g/l. In comparison, the content of αs1-casein in cow milk is about 10 g/l. β-lactoglobulin present in donkey milk is a monomer, while in milk of ruminants it is a dimer. Like human milk, it contains a substantial amount of lactose (about 7%), which determines its flavour and facilitates calcium absorption. The high lysozyme content (about 1 g/l) gives it antibacterial properties (compared to trace amounts in ruminants). Camel milk is also more digestible and induces fewer allergic reactions, because it lacks β-lactoglobulin, and its β-casein has a different structure. It also contains (compared to cow milk) more antibacterial substances such as lysozyme, lactoferrin and immunoglobulins, and furthermore the number of immunoglobulins is compatible with human ones. Goat milk components have a higher degree of assimilability as compared to cow milk. Its main protein is β-casein, with total protein content depending on the αs1-casein genetic variant. Goats with the '0' variant do not synthesize this allergenic protein. Clinical and immunochemical studies indicate, however, that it cannot be a substitute for cow milk without the risk of an anaphylactic reaction.

The aim of the study was to determine the effect of age of cows, i.e. subsequent lactation and stage of lactation, on bioactive whey protein content in milk of dairy cows of six primary breeds kept in Poland. In all cases the significant correlations between lactoferrin concentration in milk and stage of lactation was stated. Its content gradually increased with the course of lactation but the changes in the content of this protein were highly dependent on breed of cows, what was indicated also by high interactions between breed and stage of lactation.

Global milk production is undeniably dominated by 2 dairy breeds recognized worldwide: Holstein-Friesian and Jersey. A third breed, Simmental, serves as a dual-purpose breed. The objective of the present research was to establish potential changes in the fractional components of bovine milk protein (mainly whey) in relation to the health status of a dairy cow's mammary glands, which is closely determined by somatic cell count (SCC). The milk of 3 breeds was studied: Polish Holstein-Friesian (Black and Red-White varieties), Simmental, and Jersey. The cows were housed in freestall barns and fed according to the total mixed ration feeding system for both winter and summer periods. Milk samples were collected individually from each cow twice a year, in the winter and summer seasons. A total of 1,822 milk samples were evaluated (946 in winter and 876 in summer). The milk was examined for SCC, crude protein, casein, and whey fraction proteins (α-lactalbumin, β-lactoglobulin, lactoferrin, BSA, and lysozyme). The research material for each breed was split into 4 groups based on SCC (group I: ≤100,000 cells/mL; group II: 101,000 to 400,000 cells/mL; group III: 401,000 to 500,000 cells/mL; and group IV: 501,000 to 1,000,000 cells/mL). It was found that an increase of SCC promulgated a progressive decline in the daily yield of milk, which was significantly true for the Polish Holstein-Friesian. The level of crude protein decreased slightly as SCC increased, and casein concentration (r=-0.591) also followed this trend of decline. Elevation of SCC produced a decrease of major albumins (i.e., α-lactalbumin and β-lactoglobulin). However, SCC increase induced an increase in the immunoactive proteins (lactoferrin and lysozyme) as well as BSA. The interactions of a breed with increased SCC, which can be measured based on the BSA content of the milk, has indicated various levels of susceptibility to the increase in different breeds. This is confirmed by different values of correlation coefficients for these relationships: 0.71 in the Holstein-Friesian, 0.58 in Simmental, and 0.47 in the Jersey cows. Holstein-Friesian cows are more sensitive to mammary gland infections causing a greater decline of their daily milk yields, which, in turn, is reflected in an increase of the negative value of the correlation coefficients between SCC and milk efficiency (-0.24). In the other 2 breeds, the correlations were also negative, but substantially lower (-0.12 and -0.15)., (Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The analysis of nutritional value and selected traits of technological suitability of milk was performed on the basis of the available literature. This analysis concerned various animal species used for dairy purposes (cattle, buffalo, goats, sheep, camels, donkeys, and horses). It has been stated that a considerable diversity exists in the analyzed parameters and traits of milk, which results in various directions of milk utilization. Cow milk accounts for more than 80% of world milk production. It is the most universal raw material for processing, which is reflected in the broadest spectrum of manufactured products. Sheep and buffalo milk, regarding their high content of protein, including casein, and fat, make a very good raw material for processing, especially cheesemaking. Donkey and horse milk have the most comparable protein composition to human milk (low content of casein, lack of αs1-casein fraction and β-lactoglobulin, and high content of lysozyme). Donkey milk is additionally characterized by a fatty acid profile distinctive from milk of other analyzed animal species. Camel milk also has valuable nutritional properties as it contains a high proportion of antibacterial substances and 30 times higher concentration of vitamin C in comparison to cow milk. The composition of goat milk allows using it as the raw material for dairy processing and also to some extent as a therapeutical product (low content or lack of αs1-casein). [ABSTRACT FROM AUTHOR]