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From http://classes.aces.uiuc.edu/AnSci308/HumanLact.html

Macronutrient Composition of Human Milk

                        Human vs. Bovine Milk Composition


               Component        Human Milk      Bovine Milk
               Carbohydrates
                  Lactose          7.3 g/dl     4.0 g/dl
                  Oligosaccharides 1.2 g/dl     0.1 g/dl
               Proteins
                  Caseins          0.2 g/dl     2.7 g/dl
                  a-Lactalbumin    0.2 g/dl     0.1 g/dl
                  Lactoferrin      0.2 g/dl     Trace
                  Secretory IgA    0.2 g/dl     0.003 g/dl
                  beta-Lactoglobulin  None      0.36 g/dl
               Milk Lipids
                  Triglycerides    4.0 %        4.0 %
                  Phospholipids    0.04 %       0.04 %
               Minerals
                  Sodium           5.0 mM       15 mM
                  Potassium        15.0 mM      45 mM
                  Chloride         15.0 mM      35 mM
                  Calcium          8.0 mM       30 mM
                  Magnesium        1.4 mM       4.0 mM


Human milk proteins: Human milk has a relatively low casein content,
approximately 0.2 g/dl in mature milk, probably reflecting the relatively
slow growth rate of the human infant. Most of the casein in human milk is
bound in micellar form with calcium and phosphate. The other major milk
proteins that are synthesized in the mammary gland are a-lactalbumin and
lactoferrin, both present at a concentration of about 0.2 g/dl in mature
human milk. Lactoferrin is an iron-binding protein found in high
concentration in human colostrum and milk. It is considered to be a
protective factor in milk because of its anti-bacterial properties. Only
about 5% of its iron-binding capacity is occupied so that one mechanism of
bacteriostasis is thought to be binding of iron needed by bacteria to
multiply. Lactoferrin concentration in the mammary secretion is increased in
colostrum, during mastitis and following involution. The fourth major milk
protein is secretory immunoglobulin A (sIgA) also present in mature milk at
a concentration of about 0.2 g/dl. This protein is synthesized by cells of
the immune system and transported into milk by a specific mechanism
described below. It is also thought to act as a protective factor; its
concentration is much higher in colostrum (up to 10 g/dl) and in
post-involutional secretion than in mature milk.  Other proteins include
lysozyme (particularly high activity in human milk), lipases, growth factors
and many others.

From: http://www.nalusda.gov/ttic/tektran/data/000003/63/0000036318.html

The valued texture of goat's milk products has been attributed to the
peculiar distribution of caseins, the major proteins in milk; i.e.,
there is an "apparent" lack of alpha-s1 casein, which is the major
component of cow's casein. This fact is now disputed as a result of
recent Italian studies. This study developed a rapid and unequivocal
test for quantification of the relative amounts of each kind of casein
in goat's milk. The results showed that in the U.S. there are distinct
types of goat's milk with respect to the alpha-s1 content and that a
second type of casein increases when the alpha-s1 content decreases.
The amounts of these proteins in milk appear to be inherited
regardless of breed.