Protein and fat composition of mare's milk: Some nutritional remarks with reference to human and cow's milk

Abstract

Milk composition of mammallian species varies widely with reference to genetic, physiological and nutritional factors and environmental conditions. In this survey, the composition of mare's milk is reviewed and compared to human and cow's milk, considering principal protein fractions and fatty acid content. Protein content in mare's milk is higher than in human milk and lower than in cow's milk; casein concentration in mare's milk is intermediate between the other two milks. Fat content is lower in mare's milk compared to human and cow's milk. Distribution of di- and tri-glycerides in mare's and women’ milk is similar. The proportion of polyunsaturated fatty acids in mare's and human milk is remarkably higher than in cow's milk. Mare's milk shows some structural and functional peculiarities that make it more suitable for human nourishment than cow's milk.

Full text

International Dairy Journal 12 (2002) 869–877
Review
Protein and fat composition of mare’s milk: some nutritional
remarks with reference to human and cow’s milk
Massimo Malacarne, Francesca Martuzzi, Andrea Summer*, Primo Mariani
Scienze Zootecniche e Qualit "
a delle Produzioni Animali-Dip. Produzioni Animali, Biotecnologie Veterinarie, Qualit "
a e Sicurezza degli Alimenti,
Universit "
a degli Studi, via del Taglio 8, 43100 Parma, Italy
Received 4 February 2002; accepted 31 July 2002
Abstract
Milk composition of mammallian species varies widely with reference to genetic, physiological and nutritional factors and
environmental conditions. In this survey, the composition of mare’s milk is reviewed and compared to human and cow’s milk,
considering principal protein fractions and fatty acid content. Protein content in mare’s milk is higher than in human milk and lower
than in cow’s milk; casein concentration in mare’s milk is intermediate between the other two milks. Fat content is lower in mare’s
milk compared to human and cow’s milk. Distribution of di- and tri-glycerides in mare’s and women’ milk is similar. The proportion
of polyunsaturated fatty acids in mare’s and human milk is remarkably higher than in cow’s milk. Mare’s milk shows some
structural and functional peculiarities that make it more suitable for human nourishment than cow’s milk.
r2002 Elsevier Science Ltd. All rights reserved.
Keywords: Mare’s milk; Protein fractions; Fatty acids; Nutritional remarks
Contents
1. Introduction . . . . . . . . ........................................ 870
2. Gross composition . . . . . ........................................ 870
3. Protein fractions . . . . . . ........................................ 871
3.1. Main components . . . . . . . ................................... 871
3.2. Whey proteins . . . . . . . . . ................................... 871
3.3. Caseins and micelles size . . . . ................................... 872
4. Lipid composition . . . . . ........................................ 872
4.1. Triglycerides . . . . . . . . . . ................................... 873
4.2. Phospholipids . . . . . . . . . . ................................... 873
4.3. Sterols . . . . . . . . . . . . . ................................... 873
4.4. Fatty acids . . . . . . . . . . . ................................... 873
4.5. Polyunsaturated fatty acids . . . ................................... 874
4.6. Conjugated linoleic acid group . ................................... 874
5. Conclusions . . . . . . . . . ........................................ 874
Acknowledgement . . . . . . . . ........................................ 875
References . . . . . . . . . . . . ........................................ 875
*Corresponding author. Tel.: +39-0521-032613; fax: +39-0521-032611.
E-mail address: summer@unipr.it (A. Summer).
0958-6946/02/$ - see front matter r2002 Elsevier Science Ltd. All rights reserved.
PII: S 0958-6946(02)00120-6

1. Introduction
Mare’s milk, besides being the most important
nutritional resource for foals during the first months
of life, is also one of the most important basic foodstuffs
for the human populations in those areas of central
Asia, where a lactic-alcoholic beverage called Koumiss is
traditionally produced through fermentation (Storch,
1985; Orskov, 1995; Montanari, Zambonelli, Grazia,
Kamesheva, & Shigaeva, 1996; Montanari, Zambonelli,
& Fiori, 1997). This ancient beverage which Scythian
tribes used to drink some 25 centuries ago, is widely
consumed throughout Eastern Europe and Asiatic
regions (Koroleva, 1988) and is now produced on an
industrial scale (Tamime, Muir, & Wszolek, 1999). In
Western Europe, where the most important product of
equine breeding is the foal, studies on mare’s milk have
been concerned mainly with the growth and health of
the newborn horse. In the last several years, interest has
been increasing in the use of mare’s milk for human
nutrition particularly in France and in Germany
(Drogoul, Prevost, & Maubois, 1992). Recently, milk
is being studied in Italy as well as a possible substitute
for cow’s milk or as formulas for allergic children
(Businco et al., 2000; Curadi, Giampietro, Lucenti, &
Orlandi, 2001) and to find a new exploitation for local
equine breeds (Pinto, Faccia, Di Summa, &
Mastrangelo, 2001).
The aim of this review is to compare the composition
of mare’s milk to human and cow’s milk and to discuss
several parameters that could be of interest in terms of
human nutrition.
2. Gross composition
Milk represents the essential source of nourishment of
mammals during the neonatal period, the preferential
aliment. Gross composition of milk varies considerably
from species to species, as mammary secretion is
physiologically and structurally correlated to the nutri-
tional requirements of the newborns of each species.
The gross composition of mare’s, human and cow’s
milk (Table 1) shows remarkable quantitative differ-
ences in terms of the nutritional value. Mare’s milk has
noticeably less fat content when compared to human
and cow’s milk. The lactose content of mare’s milk is
similar to that of human milk and higher than that of
cow’s milk. On the other hand mare’s and human ‘ milk
are poorer in protein and mineral salt content when
compared to cow’s milk. The energy supply of mare’s
milk is clearly lower than that of human milk, which in
turn is comparable to that of cow’s milk (Neseni, Flade,
Heidler, & Steger, 1958; Neuhaus, 1959; Jenness &
Sloan, 1970; Alais, 1974; Doreau & Boulot, 1989;
Mariani, Martuzzi, & Catalano, 1993; Solaroli, Pagliar-
ini, & Peri, 1993; Salimei, 1999) (Table 1).
Mare’s and human milk are quite similar in terms of
sugar supply, including galactose, a constituent of the
myelinic sheath of the central nervous system cells. The
structural complexity of the minor carbohydrate frac-
tions (e.g. growth-promoting factor of Bifidobacterium
bifidum) (Alais, 1974; Kunz, Rodriguez-Palmero,
Koletzko, & Jensen, 1999) of human milk makes a
functional comparison with cow’s and mare’s milk
difficult, and this aspect has not been sufficiently studied
in mare’s milk (Urashima, Saito, & Kimura, 1991) from
this point of view. Sialic acid is a component that affects
intestinal flora development and, most probably, the
level of glycosylation of gangliosides of the brain and
central nervous system (Ziegler, 1960; Nakano, Suga-
wara, & Kawakami, 2001), The values found in human
milk (B100 mg) are significantly higher than that found
in cow’s (B20 mg) and mare’s (B5 mg100 mL
1
) milk
(Morrissey, 1973; Kulisa, 1986; Heine, Wutzke, &
Radke, 1993).
Whole protein and salt content are comparable
between mare’s and human milk, while cow’s milk is
clearly richer in salts, and thus less suitable as a
replacement for human milk. From these several
considerations on the gross composition, mare’s milk
would appear to be, on the whole, a more suitable
nourishment for infants than cow’s milk (Stoyanova,
Abramova, & Ladodo, 1988; Marconi & Panfili, 1998).
Table 1
Gross composition of mare’s milk in comparison to human and cow’s milk
Mare Human Cow
Fat (g kg
1
) 12.1 (5–20) 36.4 (35–40) 36.1 (35–39)
Crude protein (g kg
1
) 21.4 (15–28) 14.2 (9–17) 32.5 (31–38)
Lactose (g kg
1
) 63.7 (58–70) 67.0 (63–70) 48.8 (44–49)
Ash (g kg
1
) 4.2 (3–5) 2.2 (2–3) 7.6 (7–8)
Gross energy (kcal kg
1
) 480 (390–550) 677 (650–700) 674 (650–712)
Mean value, and between brackets, minimum–maximum values reported in literature.
References common to mare, human and cow: Jenness and Sloan (1970), Alais (1974), Solaroli et al. (1993) and Salimei (1999).
References only for mare: Storch (1985) and Mariani et al. (1993).
M. Malacarne et al. / International Dairy Journal 12 (2002) 869– 877870

Qualitative differences between the milks of these
species are undoubtedly much more striking, when
single structural components are considered, with
particular regard to protein fractions and lipid
composition.
3. Protein fractions
3.1. Main components
The whole protein system of mare’s milk is quite
similar to that of human milk. Both whey protein in toto
and NPN concentrations are comparable. Cow’s milk,
on the other hand, has a higher casein content, and is
thus defined as a cas!
eineux milk (definition of French
Authors) (Alais, 1974; Boland, Hill, & Creamer, 1992;
Mariani et al., 1993; Pagliarini, Solaroli, & Peri, 1993;
Doreau, 1994; Csap !
o-Kiss, Stefler, Martin, Makray, &
Csap!
o, 1995; Martuzzi, Tirelli, Summer, Catalano, &
Mariani, 2000) (Table 2).
The whey protein fraction, indeed, represents ap-
proximately 40% in mare’s milk, slightly more than
50% in human milk and less than 20% in cow’s milk.
Cow’s milk protein features, like other ruminant milks
(e.g. goat and sheep), are quite different, as charac-
terised by an acid-enzymatic, mixed coagulation.
From this point of view mare’s milk is more similar to
human milk, which could be defined typically as
albumineux. The richness in whey protein content of
mare’s milk makes it more favourable to human
nutrition than cow’s milk, because of the relatively
higher supply of essential amino acids (Hambræus,
1994).
3.2. Whey proteins
The whey protein pattern clearly shows the physiolo-
gical specificity of different mammary secretions; as seen
by both the concentration and distribution of the
single proteins and whey enzymes (Minieri & Intrieri,
1970; L.
onnerdal, 1985; Boland et al., 1992; Pagliarini
et al., 1993; Solaroli et al., 1993; Martuzzi et al., 2000)
(Table 3).
Human milk is devoid of b-lactoglobulin, while this
protein is present in significant amounts in both cow’s
Table 3
Whey proteins distribution
a
of mare’s milk in comparison to human and cow’s milk
Mare Human Cow
True whey protein (g kg
1
) 8.3 7.6 5.7
b-lactoglobulin (%) 30.75 (25.3–36.3) Absent 20.10 (18.4–20.1)
a-lactalbumin (%) 28.55 (27.5–29.7) 42.37 (30.3–45.4) 53.59 (52.9–53.6)
Immunoglobulins (%) 19.77 (18.7–20.9) 18.15 (15.1–19.7) 11.73 (10.1–11.7)
Serum albumin (%) 4.45 (4.4–4.5) 7.56 (4.5–9.1) 6.20 (5.5–76.7)
Lactoferrin (%) 9.89 30.26 8.38
Lysozyme (%) 6.59 1.66 Trace
Mean value, and between brackets, minimum–maximum values reported in literature.
References common to human and cow: Boland et al. (1992) and Solaroli et al. (1993).
References only for mare: Pagliarini et al. (1993) and Martuzzi et al. (2000).
Reference only for human: L.
onnerdal (1985).
a
Proteose-peptone fraction was not reported in the considered references.
Table 2
Main nitrogen fractions of mare’s milk in comparison to human and cow’s milk
Mare Human Cow
Crude protein (g kg
1
) 21.4 (15–28) 14.2 (9–17) 32.5 (31–38)
True whey protein (g kg
1
) 8.3 (7.4–9.1) 7.6 (6.8–8.3) 5.7 (5.5–7.0)
Casein (g kg
1
) 10.7 (9.4–12.0) 3.7 (3.2–4.2) 25.1 (24.6–28.0)
NPN 6.38 (g kg
1
) 2.4 (1.7–3.5) 2.9 (2.6–3.2) 1.7 (1.0–1.9)
True whey protein (%) 38.79 53.52 17.54
Casein (%) 50.00 26.06 77.23
NPN 6.38 (%) 11.21 20.42 5.23
Mean value and, between brackets, minimum–maximum values reported in literature.
References common to mare, human and cow: Doreau (1994).
References common to human and cow: Alais (1974) and Boland et al. (1992).
References only for mare: Mariani et al. (1993), Pagliarini et al. (1993), Csap!
o-Kiss et al. (1995) and Martuzzi et al. (2000).
M. Malacarne et al. / International Dairy Journal 12 (2002) 869– 877 871

and mare’s milk. This protein is responsible for the onset
of allergic forms to milk proteins that affect a significant
percentage of infants nourished with maternal milk
replacements (cow milk formulas) (Businco & Bellanti,
1993; S!
elo et al., 1999). This problem seems to occur less
often when mare’s milk is used (Konig, 1993; Businco
et al., 2000).
Antimicrobial defence in mare’s milk seems to be due
mainly to the presence of lysozyme (as in human milk)
and, to a lesser degree, to lactoferrin, which is
preponderant in human milk (Solaroli et al., 1993; de
Oliveira, de Araujo, Bao, & Giugliano, 2001). These
antimicrobial factors are scarce in cow’s milk, where
immunoglobulins represent the principal defense against
microbes and are particularly abundant in colostrum
(Boland et al., 1992; Solaroli et al., 1993).
3.3. Caseins and micelles size
Current data has defined only an approximation of
the percentage distribution of mare’s milk caseins
(Visser, Jenness, & Mullin, 1982; Ochirkhuyag, Chobert,
Dalgalarrondo, & Haertl!
e, 2000). Mare’s milk casein is
composed mainly of equal amounts of b-casein and a
s
-
casein (Abd El-Salam, Farag, El-Dein, Mahfouz, &
El-Etriby, 1992; Ochirkhuyag et al., 2000) (Table 4),
which have been recently characterised (Egito et al.,
2002). The proportions of the main a
s
-casein fractions,
i.e. as1- and as2 -casein, is still under study (Malacarne,
Summer, Formaggioni, & Mariani, 2000; Egito et al.,
2002). Recently, mare k-casein has also been identified
and characterised (Egito et al., 2002; Iametti, Tedeschi,
Oungre, & Bonomi, 2001). It shows several biochemical
properties similar to that of bovine and human k-casein,
such as the presence of carbohydrate moieties and
susceptibility to hydrolysis by chymosin (group II)
(Egito et al., 2001). The proportion of k-casein in
mare’s milk appears to be lower compared to that of
cow’s and human milks (Egito et al., 2001).
Bovine casein composition (Creamer, 1991; Boland
et al., 1992) is well known: it is relatively richer in as1-
casein, a fraction believed to be responsible for the onset
of allergic forms in children (Mercier, 1986; Whitelaw
et al., 1990). Both mare’s and cow’s casein outlines differ
from that of human milk (Creamer, 1991; Boland et al.,
1992; Cuilliere, Tregoat, Bene, Faure, & Montagne,
1999), being characterised by a clear prevalence of
b-casein. However mare’s casein could be considered
relatively rich in b-casein as well, and thereby able to
supply children with abundant amounts of casomor-
phins (Clare & Swaisgood, 2000).
Mare’s milk micelles are the largest as compared to
both human and cow’s milk micelles (Buchheim, Lund,
& Scholtissek, 1989). Micellar structure varies consider-
ably from species to species. In cow’s and mare’s milk it
has a spongy structure, while in human milk it is
reticular, fairly regular and very loose, due to numerous
canals and caverns (Jasi !
nska & Jaworska, 1991). This
affects susceptibility to pepsin hydrolysis, which, how-
ever, depends mainly on the high b-casein micellar
content.
The different protein composition in toto (casein
content and whey protein/casein ratio) and the different
micellar structure (caseins distribution and micelles size)
determine marked differences in the rheological proper-
ties of the curds obtained from each of the milks under
consideration, and consequently influence the digestive
utilisation of milk nutrients. Mare’s and human milk
forms a finer, softer precipitate, which is physiologically
more suitable for infant nutrition because it is more
easily digestible than the firm coagulum of cow’s milk
(Kalliala, Seleste, & Hallman, 1951; Solaroli et al.,
1993).
4. Lipid composition
The fat content of mare’s milk is very low when
compared to that of human and cow’s milk (Table 1).
Table 4
Caseins distribution of mare’s milk in comparison to human and cow’s milk
Mare Human Cow
Casein (g kg
1
) 10.7 3.7 25.1
a
s
-casein (%) 46.65 (40.2–59.0) 11.75 (11.1–12.5) 48.46
a
(48.3–48.5)
b-casein (%) 45.64 (40.1–51.4) 64.75 (62.5–66.7) 35.77 (35.8–37.9)
k-casein (%) (7.71)
b
23.50 (22.2–25.0) 12.69
c
(12.7–13.8)
Micelles size (nm) 255 64 182
Mean value and, between brackets, minimum–maximum values reported in literature.
References common to mare, human and cow: Buchheim et al. (1989).
References common to human and cow: Creamer (1991) and Boland et al. (1992).
References only for mare: Abd El-Salam et al. (1992) and Ochirkhuyag et al. (2000), Malacarne et al. (2000).
Reference only for human: Cuilliere et al. (1999).
a
38.46 as1-casein and 10.00 as2 -casein.
b
k-casein and other fractions not characterised.
c
100% was reached with g-casein fraction (3.08%).
M. Malacarne et al. / International Dairy Journal 12 (2002) 869– 877872

Lipids in milk are dispersed as emulsified globules; in
mare’s milk, fat is organised in globules of about 2-3 mm
of size (Kharitonova, 1978; Welsch, Buchheim, Schu-
macher, Schinko, & Patton, 1988). Fat globules are
coated with three layers: an internal protein layer, an
intermediate layer consisting of a phospholipid mem-
brane and the external layer consisting of high-
molecular-weight glycoproteins. On the surface of these
glycoproteins there is a branched oligosaccharide
structure, which is similar to that of the fat globules in
human milk and which is not found in cow’s milk
(Solaroli et al., 1993).
In human milk, fat globules have an average diameter
of about 4 mm. The external membrane is coated with an
array of glycoprotein filaments, similar to that of mare’s
milk, that may enhance digestion by binding lipases
(Jensen, Ferris, & Lammi-Keefe, 1992; Koletzko &
Rodriguez-Palmero, 1999). In cow’s milk the globules
have an average diameter of 3–5 mm (Welsch et al.,
1988), and are coated by a thin protective film, with
external layers constituted of proteins and phospholi-
pids (Jensen, Ferris, Lammi-Keefe, & Henderson, 1990).
4.1. Triglycerides
Mare’s milk lipids are less rich in triglycerides (about
80% of total) than human and cow’s milk (about 98%
in both milks) (Pastukhova & Gerbeda, 1982; Doreau &
Boulot, 1989; Jensen et al., 1992) (Table 5). The number
of carbon atoms in di- and tri-glycerides is a character-
istic that varies from species to species (Parodi, 1982). In
mare’s and human milk fat the distribution follows a
typical unimodal pattern (maximum at 50–52 carbon
atoms), whereas in cow’s milk it follows a bimodal
pattern (first maximum ranging from 34 to 40 carbon
atoms and the second from 42 to 54) (Pagliarini et al.,
1993).
From a nutritional point of view, the triglyceride
structure is a principal factor influencing the action of
lipolytic enzymes and, therefore, fat absorption. In
human milk, palmitic acid (C
16:0
) is preferably located in
the sn-2 position which is considered favourable by
some authors for the assimilation of this fatty acid in
children (Lien, Yuhas, Boyle, & Tomarelli, 1993;
Winter, Hoving, & Muskiet, 1993). However, this has
not yet been definitively confirmed (Jensen et al., 1992).
In mare’s milk C
16:0
is also preferentially associated with
the sn-2 position (Parodi, 1982). On the other hand C
16:0
in cow’s milk is equally located in 1 and 2 positions.
4.2. Phospholipids
Phospholipids, complex compounds constituted
mainly by polyunsaturated fatty acids, are present in
all living cells as components of the lipoprotein layers of
the cell membrane, in particular of neural cells (Alais,
1974). Mare’s milk is richest in phospholipids when
compared to human and cow’s milk (Pastukhova &
Gerbeda, 1982) (Table 5). The phospholipid composi-
tion of mare’s milk (Kharitonova, 1978) is different
from both human and cow’s milk (Jensen et al., 1990).
Compared to human milk, phospholipids of mare’s milk
are relatively richer in phosphatidylethanolamine (31%
vs 20%) and in phosphatidylserine (16% vs 8%), and
less rich in phosphatidylcholine (19% vs 28%) and
phosphatidylinositol (trace vs 5%); sphingomyelin
proportion is similar (34% mare vs 39% human ).
4.3. Sterols
Mare’s milk seems to have a higher proportion of the
unsaponifiable fraction (Pastukhova & Gerbeda, 1982)
in comparison to cow’s and human milk (Table 5). The
unsaponifiable content is lower in human milk, whereas
the value of mare’s milk would be similar to that of
cow’s milk. The sterol fraction in mare’s, human and
cow’s milk is constituted partially by cholesterol (about
0.3–0.4% of the lipid content in all milks) (Travia, 1986;
Jensen et al., 1990; Pagliarini et al., 1993).
4.4. Fatty acids
Compared to human and cow’s milk (Alais, 1974;
Travia, 1986; Solaroli et al., 1993), mare’s milk fat
(Antila, Kyl.
a-Siurola, Uusi-Rauva & Antila, 1971;
Kulisa, 1977; Doreau, Boulot, Bauchart, Barlet &
Martin-Rosset, 1992; Doreau, Boulot, & Chilliard,
1993; Intrieri & Minieri, 1970; Csap !
o, Stefler, Martin,
Makray, & Csap !
o-Kiss., 1995; Salimei, Bontempo, &
Dell’Orto, 1996; Mariani, Martuzzi, Summer, & Cata-
lano, 1998; Martuzzi, Summer, Catalano, Barbacini, &
Mariani, 1998) is especially poorer in stearic and oleic
acids, and richer in palmitoleic, linoleic and linolenic
acids (Table 6). Like human milk, and different from
cow’s milk, mare’s milk has a lower proportion of
saturated fatty acids with a low and high number of
carbon atoms (C
4:0
;C
6:0
;C
16:0
;C
18:0
).
Table 5
Lipids composition of mare’s milk in comparison to human and cow’s
milk (mean value)
Mare Human Cow
Fat (g kg
1
) 12.1 36.4 36.1
Triglycerides (%) 81.1
a
98.0 97.0
Phospholipids (%) 5.0 1.3 1.5
Unsaponifiable (%) 4.5
b
0.7 1.5
Free fatty acids (%) 9.4 Trace Trace
Reference only for mare: Pastukhova and Gerbeda (1982).
Reference only for human: Jensen et al. (1990).
Reference only for cow: Alais (1974).
a
Mono- and di-glycerides 1.8%.
b
Non identified fractions 0.3%.
M. Malacarne et al. / International Dairy Journal 12 (2002) 869– 877 873

On the whole, the percentage of unsaturated fatty
acids in mare’s and human milk is similar and higher
than that in cow’s milk. This is due mainly to a high
content in polyunsaturated fatty acids (PUFA) with
intermediate and high numbers of carbon atoms; this
high unsaturation could represent a nutritional advan-
tage (Solaroli et al., 1993). The percentage of mono-
unsaturated fatty acids in mare’s milk is lower than
human milk, and similar to cow’s milk (Table 7). Free
fatty acids are found in mare’s milk in marked amounts,
while only traces are present in human and cow’s milk
(Pastukhova & Gerbeda, 1982) (Table 5).
4.5. Polyunsaturated fatty acids
The fat composition of mare’s milk is particular when
compared with other species, due to the high content in
linoleic and especially linolenic polyunsaturated fatty
acids (Alais, 1974; Travia, 1986; Doreau & Boulot, 1989;
Martuzzi et al., 1998) (Table 7). Linoleic acid (C
18:2
), of
the omega-6 group, and alpha-linolenic acid (C
18:3
)of
the omega-3 group, are considered essential fatty acids
because animal organisms are unable to synthesise these
compounds (Mussa & Meineri, 1997; Svahn, Feldl,
R.
aih.
a, Koletzko & Axelsson, 2002), which have
important biological functions. Research with humans
has indicated a role for linoleic acid as a precursor of
prostaglandin E, in the prevention of gastric ulcers
(Grant, Palmer, Kelly, Wilson, & Misiewicz, 1988).
PUFA are precursors of long-chain polyunsaturated
fatty acids (LC-PUFA), indispensable structural com-
ponents of all cellular membranes. Moreover, some LC-
PUFA are precursors of eicosanoids, molecules with a
potent biological activity which modulates various
cellular and tissue processes (Koletzko & Rodriguez-
Palmero, 1999). The properties attributed to mare’s milk
and Koumiss as curative substances for hepatitis,
chronic ulcer and tuberculosis (Storch, 1985; Solaroli
et al., 1993) may be due to the high concentration of
such compounds.
4.6. Conjugated linoleic acid group
Milk fat is an important source of potential antic-
arcinogens from the naturally occurring conjugated
linoleic acid (CLA) group. Mare’s milk is nearly CLA-
free (mean value 0.09% of total fatty acids). CLA
content in human milk has been reported to vary from
0.2 to 1.1%. In cow’s milk values ranging from 0.2 to
2.4% have been reported (Jensen et al., 1992; Jahreis
et al., 1999).
5. Conclusions
Compared to human and cow’s milk, mare’s milk has
a lower energy value, due to a lower fat supply, while the
sugar content is similar in both mare’s and human milk.
The whole protein and salt supply of mare’s milk is
Table 7
PUFA of mare’s milk in comparison to human and cow’s milk
Mare Woman Cow
Saturated fatty acids (%) 55.8 54.8 68.0
-C
4
,C
6
,C
8
(%) 3.9 0.6 5.4
-C
10
,C
12
,C
14
,C
16
,C
18
(%) 51.9 54.2 62.6
Unsaturated fatty acids (%) 44.2 45.2 32.0
C
16:1
,C
18:1
(%) 25.2 37.1 28.0
C
18:2
,C
18:3
(%) 19.0 8.1 4.0
References: see Table 6.
Table 6
Percentages of fatty acids relatives to total fatty acids of mare’s milk in comparison to human and cow’s milk
Mare Human Cow
C
4
Butyric (%) 0.2 0.1 1.4 (1.4–3.3)
C
6
Caproic (%) 0.4 0.2 2.1 (1.6–2.2)
C
8
Caprylic (%) 3.3 (1.0–5.9) 0.3 (0.1–0.3) 1.7 (1.3–1.8)
C
10
Capric (%) 8.6 (3.7–15.1) 2.0 (1.1–2.1) 3.5 (3.0–3.6)
C
12
Lauric (%) 9.3 (3.5–14.7) 6.8 (3.1–7.2) 3.9 (3.1–4.0)
C
14
Myristic (%) 8.5 (4.6–10.2) 10.4 (5.1–10.9) 12.6 (13.0–14.2)
C
16
Palmitic (%) 23.8 (19.7–27.9) 28.1 (20.2–29.6) 29.5 (30.2–42.7)
C
16:1
Palmitoleic (%) 6.1 (3.9–9.7) 3.5 (3.7–5.7) 1.7
C
18
Stearic (%) 1.7 (1.1–3.1) 6.9 (6.0–8.6) 13.3 (5.7–13.7)
C
18:1
Oleic (%) 19.1 (12.1–28.3) 33.6 (33.3–46.4) 26.3 (16.7–27.1)
C
18:2
Linoleic (%) 9.6 (5.1–15.5) 6.4 (6.0–13.0) 2.9 (1.6–3.0)
C
18:3
Linolenic (%) 9.4 (2.8–15.7) 1.7 (1.0–3.4) 1.1 (0.5–1.8)
Mean value and, between brackets, minimum–maximum values reported in literature.
References common to human and cow: Alais (1974), Travia (1986), Jensen et al. (1990), Solaroli et al. (1993).
References only for mare: Antila et al. (1971), Kulisa (1977), Doreau et al. (1992, 1993), Intrieri and Minieri (1970), Csap!
o et al. (1995), Salimei et al.
(1996), Mariani et al. (1998), Martuzzi et al. (1998).
M. Malacarne et al. / International Dairy Journal 12 (2002) 869– 877874

similar to that of human milk, whereas cow’s milk,
richer in salts, is less suitable as a replacement for
mother’s milk.
The whole protein system of mare’s milk, regarding
both whey protein in toto and NPN concentrations, is
similar to human milk as well, whereas cow’s milk
differs from both for higher casein content. The richness
and pattern of the whey protein of mare’s milk make it
more favourable than cow’s milk for human nourish-
ment. Mare’s milk casein is composed of nearly equal
parts of b-casein and as-casein; human milk is char-
acterised by a prevalence of b-casein; cow casein is
relatively richer in as1-casein, which is believed to be
responsible for the onset of allergic forms in nursing
infants. Through the concurrence of several structural
factors, mare’s and human milk form a finer, softer
precipitate, more easily digestible than the firm coagu-
lum of cow’s milk.
The external layer of mare’s and human milk fat
globules and the distribution of di- and tri-glycerides in
mare’s and human milk are similar. The percentage of
unsaturated fatty acids in mare’s and human milk is
higher than that in cow’s milk; due mainly to a high
content in polyunsaturated fatty acids with an inter-
mediate and high number of carbon atoms (PUFA).
Despite the need for further studies on the properties
and composition of mare’s milk, it is possible to
conclude from these few considerations that mare’s
milk is, on the whole, more suitable than cow’s milk as
nourishment for infants.
Acknowledgements
Authors thank Dr. Laura Helen Kramer for the
revisions of the English version of this paper.
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