BLBS102-c26 BLBS102-Simpson March 21, 2012 13:51 Trim: 276mm X 219mm Printer Name: Yet to Come
510 Part 4: MilkTable 26.8.Principal Oligosaccharides of Equine ColostrumOligosaccharide (mg/L)Acidic
Neu5Ac(α2–3) Gal(β1—4)Glc N/a
Gal(β1–4)GlcNAcα1-diphosphate (N-acetyllactosamine-α1-phospahte) N/aNeutral
Gal(β1–3)Gal(β1–4)Glc (β3’-galactosyllactose) 7.8
Gal(β1–6)Gal(β1–4)Glc (β6’-galactosyllactose) 4.8
Gal(β1–4)GlcNAc(β1–3)Gal(β1–4)Glc (lacto-N-neotetraose) N/a
Gal(β1–4)GlcNAc(β1–6)Gal(β1–4)Glc (iso-lacto-N-neotetraose) 0.5
Gal(β1–4)GlcNAc(β1–6)[Gal(β1–3)]Gal(β1–4)Glc (lacto-N-novopentanose 1) 1.1
Gal(β1–4)GlcNAc(β1–6)[Gal(β1–4)GlcNAc(β1–3)]Gal(β1–4)Glc (lacto-N-neohexaose) 1.1
Gal(β1–4)GlcNAc-1-phosphate (N-acetyllactosamine-1–0-phosphate) N/a
Neu5Ac(α2–3)Gal(β1–4)Glc (3’-N-acetylneuraminyllactose) N/aSource: From Urashima et al. 1989, 2001, Nakamura et al. 2001.
Gal,d-galactose; Glc,d-glucose; GlcNAc,N-acetylglucosamine; Neu5A,N-acetylneuraminic acid; N/a, not available.including as important components of our immune system and as
prebiotics to promote a healthy gut microflora (Donovan 2009).
Bovine, ovine, caprine and equine milk contain relatively low
levels of OSs, which have been characterised (see Urashima et al.
2001). The OSs identified in equine colostrum are summarised
in Table 26.8. The OSs in mature equine milk have not been re-
ported but it can be assumed that the level is considerably lower
than in colostrum which has approximately 18.6 g/L (Nakamura
et al. 2001). The neutral OSs, lacto-N-neotetraose and lacto-N-
neohexaose, in equine colostrum are also abundant in human
milk, while iso-lacto-N-neotetraose and lacto-N-novopentanose
1 are not, but have been identified in bovine colostrum; the latter
has been identified also in the milk of the Tammar wallaby and
brown capuchin monkey (Urashima et al. 2009).LIPIDS
Milk fat is important for the provision of energy to the new-
born as well as being the vehicle for fat-soluble vitamins and
essential fatty acids. From a practical point of view, milk lipids
are important as they confer distinctive nutritional, textural and
organoleptic properties on dairy products. Dietary composition
is considered one of the major determinants of the fatty acid
composition of equid milk and non-dietary factors such as stage
of lactation, age and parity of the mare play minor roles.
Triglycerides (TGs) represent approximately 80–85% of the
lipids in equine and asinine milk, while approximately 9.5% are
free fatty acids (FFAs) and approximately 5–10% are phospho-
lipids (Jahreis et al. 1999). In contrast, approximately 97–98%
of the lipids in bovine and human milk are TGs, with low lev-
els of phospholipids and free fatty acids, 1.3 and 1.5 g.100g−^1 ,
respectively. The high level of free fatty acids in equid milk
implies that rancidity is a problem with these milks and is dealt
with in Section ‘Stability of Equine Milk Fat’.
The relatively high content of phospholipids in equid milk
is thought to contribute to its buffering properties. TGs, the
primary transport and storage form of lipids, are synthesisedin the mammary gland from fatty acids that originate from
three sources:de novosynthesis (C8:0, C10:0 and C12:0), di-
rect uptake from the blood (>14 carbons) and modification
of fatty acids in the mammary gland by desaturation and/or
elongation. Circulating fatty acids in the blood may origi-
nate from dietary fat or from lipids mobilised from body fat
stores. The principal phospholipids of equid milk are phos-
phatidylcholine (19%), phosphatidylethanolamine (31%), phos-
phatidylserine (16%) and sphingomylin (34%); the correspond-
ing values for bovine milk are 35%, 32%, 3% and 25% and for
human milk are 28, 20, 8 and 39%, respectively. The high level
of FFAs in equid milk implies considerable lipolysis but this
has not been suggested; if lipolysis was responsible for the high
level of FFAs, they should be accompanied by high levels of
mono- and di-glycerides but these are reported to be quite low
at approximately 1.8% of total lipids.
Table 26.9 shows the monounsaturated fatty acids (MUFA)
and polyunsaturated fatty acids (PUFA) in the milk fat of
some ruminant and non-ruminant species. The milk fat of non-
ruminants contains substantially higher levels of PUFAs than
ruminant milks due to the lack of biohydrogenation of fatty
acids in the former, and for the two-equid species shown, the
horse has considerably more PUFAs in its milk than the donkey.
Saturated fatty acids are the dominant class in asinine milk and
levels are significantly higher than those in equine or human
milk (Table 26.9).Fatty Acids in Equid MilksThe fatty acid profile of equid milk (Table 26.10) differs from
that of bovine and human milk fat in a number of respects.
Like human, and unlike bovine milk, equid milk is characterised
by low proportions of saturated fatty acids with low or higher
numbers of carbons, that is, C4:0,C6:0,C16:0and C18:0(Pikul
and Wojtowski 2008). Butyric acid (C ́ 4:0) is present at high
levels in bovine and other ruminant milk fats, produced from