Comparison of the digestion of caseins and whey proteins in equine, bovine, caprine and human milks by human gastrointestinal enzymes

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Table I.

Protein content (g·100 g⁻¹) in bovine, caprine, human and equine milks.

Protein	Bovine	Caprine	Human	Equine
Total	3.3 ^a	2.7 ^a,b,d	0.9 ^a,b,c	2.3 ^b,c
Casein	2.72	2.27	0.47	1.39
α_s1-CN	1.0^a	0.27^a,b,d, ^*	0.06^b,c	0.25^b
α_s2-CN	0.37^a	0.41^a,b,d	Unknown^b	0.02^b
β-CN	1.0^a	1.09^a,b,d	0.31^a,b,c	1.10^b
κ-CN	0.35^a	0.50^a,b,d	0.1^a,b,c	0.025^b
Whey protein	0.57	0.40	0.52	0.92
β-lg	0.33^a	0.22^a,b	Unknown^a,b,c	0.28^b,c
α-la	0.12^a	0.12^a,b	0.18^a,b,c	0.28^b,c
LF	0.01^a	0.01^a	0.15^a,b,c	0.08^c
SA	0.04^a		0.04^a,c	0.04^c
LZ	Traces^a	Traces^a,b	0.03^a,b,c	0.08^b,c
IGs	0.07^a	0.05^a	0.12^a,c	0.16^c
Casein:whey ratio	5	6	0.9	1.5

The bold values are used to indicate the main fractions.

Mean values for data taken from (a) [22], (b) [24], (c) [21] and (d) [27].

Due to polymorphism of the α_s1-allele in goats, the amount of this protein in the milk is genotype-dependant.