Allergenicity of milk of different animal species in relation to human milk.

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-lactoglobu lin(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(about20%),and the concentration of the most allergenic casein fraction αs1 is 1.5-2.5g/l.In comparison, the content of αs1-casein in cow milk is about 10g/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(about7%),which determines its flavour and facilitates calcium absorption. The high lysozyme content(about 1g/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-case in 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 compatib le 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-casei 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.