BLBS102-c26 BLBS102-Simpson March 21, 2012 13:51 Trim: 276mm X 219mm Printer Name: Yet to Come
514 Part 4: Milkextend from the surface of the fat globules in equine and human
milk (Welsch et al. 1988). These filaments dissociate from the
surface into the milk serum on cooling and are lost on heating.
For unknown reasons, the filaments on bovine milk fat glob-
ules are lost much more easily than those in equine or human
milk. The filaments facilitate the adherence of fat globules to
the intestinal epithelium and probably improve the digestion of
fat (Welsch et al. 1988). The mucins prevent bacterial adhe-
sion and may protect mammary tissue against tumors (Patton
1999). The milk fat globules (MFGs) of asinine milk can be up
to approximately 10μm in diameter, whereas those of equine
milk are generally smaller at 2–3μm on average; the MFGs of
bovine and human milk are 3–3.5μm and approximately 4μm,
respectively. Little is known about the proteins of the MFGM
of equids but they are known to play a major role in neonatal
defense mechanisms in humans (see Mather 2000).
Butyrophilin, acidophilin and XOR have been identified in
the equine MFGM and appear to be similar to the correspond-
ing proteins of the human MFGM, as does lactadherin which
shares 74% identity with that of the human lactadherin (Barello
et al. 2008). Both XOR and acidophilin are involved in fat glob-
ule secretion with butyrophylin while lactadherin is thought to
have a protective function against rotovirus in the intestinal tract
(Barello et al. 2008). Like ovine and buffalo milk, equine milk
does not cream due to the lack of cryoglobulin.Rheology Equid Milk FatThe temperature-dependent melting characteristics of bovine
milk-fat have been studied thoroughly but since equid milk isnot used for the production of butter, the spreadability, rheology
and melting characteristics of these fats have not been studied in
detail (see Chandan et al. 1971). Considering the rather unusual
fatty acid profile of equid milk fats, they should have interesting
melting and rheological properties.Stability of Equine Milk FatLipids generally are susceptible to two forms of chemical
spoilage, lipid oxidation (oxidative rancidity) and lipolysis (hy-
drolytic rancidity) which are of great commercial significance
to the dairy industry and have been studied in detail (see Fox
and McSweeney 2006). No studies on the chemical spoilage of
equid milk-fat have been reported. Considering the high content
of PUFAs in these fats, they are probably quite susceptible to ox-
idation. Since equine milk contains a lipase, hydrolytic rancidity
would be expected under certain conditions.VITAMINS
The overall vitamin content of any milk depends on maternal
vitamin status but water-soluble vitamins are more responsive to
the maternal diet than fat-soluble vitamins. Vitamin levels in the
milk of some species are shown in Table 26.11. The level of vita-
min E is low in asinine milk (∼0.05 mg.L−^1 ) and is reduced fur-
ther if the milk is heated. Concentrations of fat-soluble vitamins
are generally similar in equine and bovine milks (Table 26.12).
The levels of vitamins A, D 3 , K and C are significantly higher in
equine colostrum than in equine milk, whereas the concentrationTable 26.11.Vitamin Levels (mg.L−^1 ) in the Milk of Some SpeciesVitamin Buffalo Goat Sheep Donkey Cow Horse HumanWater-solubleThiamine, B 1 0.5 0.49 0.48 0.41 0.37 0.3 0.15
Riboflavin, B 2 1.0 1.5 2.3 0.64 1.8 0.3 0.38
Niacin, B 3 0.8 3.2 4.5 0.74 0.9 1.4 1.7
Pantothenic acid, B 5 3.7 3.1 3.5 – 3.5 3 2.7
Pyridoxine, B 6 0.25 0.27 0.27 – 0.64 0.3 0.14
Biotin, B 7 0.11 0.039 0.09 – 0.035 – 0.006
Folic acid, B 9 0.18 0.16
Cobalamin, B 12 3.0 0.7 0.007a 1.1 0.004 0.003 0.5
Ascorbic acid, C – 9.0 4.25b – 21 17.2c 43
Fat-solubleVitamin A andβ-carotene – 0.5 0.5 – 0.32–0.50 0.12 2.0
Cholecalciferol, D 3 – – – – 0.003 0.003 0.001
α-Tocopherol, E – – – 0.05 0.98–1.28 1.128 6.6
Phylloquinone, K – – – – 0.011 0.020 0.002Source: Modified from Walstra and Jenness 1984, Souci et al. 2000.
aRamos et al. 1994.
bRecio et al. 2009.
cCsap ́o et al. 1995.