Food Biochemistry and Food Processing (2 edition)

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26 Equid Milk: Chemistry, Biochemistry and Processing 495

Table 26.1.Gross Composition of the Milk of Equid Species and Some Dairy Species, with Human and Other

Selected Species Included for Comparison

Gross Days to

Casein: Energy Double

Total Whey (kJ.kg−^1 Birth

Species Solids Protein Ratio Fat Lactose Ash or kJ.L−^1 ) Rate

aHorse (Equus caballus) 102.0 21.4 1.1:1 12.1 63.7 4.2 1883 40–60

aDonkey (Equus africanus

asinus)

88.4 17.2 1.28:1 14.0 68.8 3.9 1966 30–50

aMountain zebra (Equus

zebra hartmannae)

100.0 15.6 – 10.2 69.0 3.0 1800 –

aPlains zebra (Equus

burchelli)

113.0 16.3 – 22.0 70.0 4.0 2273 –

aPrzewalski horse (Equus

caballus przewalski)

105.0 15.5 1.1:1 15.0 67.0 3.0 1946 –

bCow (Bos taurus) 127.0 34.0 4.7:1 37.0 48.0 7.0 2763 30–47

aBuffalo (Bubalus bubalis) 172.0 46.5 4.6:1 81.4 48.5 8.0 4644 48–50

bSheep (Ovis aries) 181.0 55.9 3.1:1 68.2 48.8 10.0 4309 10–15

aGoat (Capra hircus)h 122.0 35.0 3.5:1 38.0 41.0 8.0 2719 12–19

bCamel (Camelus

dromedarius)

124.7 33.5 1.68:1 38.2 44.6 7.9 2745 250

bLlama (Llama glama) 131.0 34.0 3.1:1 27.0 65.0 5.0 2673 120

aYa k (Bos grunniens) 160.0 42.3 4.5:1 56.0 52.9 9.1 3702 60

aMan(Homo sapiens) 124.0 9.0 0.4:1 38.0 70.0 2.0 2763 120–180

bPig (Sus scrofa) 188.0 36.5 1.4:1 65.8 49.6 10.0 3917 9

bRabbit (Oryctolagus

cuniculus)

328.0 139.0 2.0:1 183.0 21.0 18.0 9581 4–6

bBlue whale (Balaenoptera

musculus)

550.0 119.0 2.0:1 409.0 13.0 14.0 17614 10

bNorthern Fur Seal

(Callorhinus ursinus)

633.0 103.0 1.1:1 507.0 1.0 5.0 20836 5

aRat (Rattus norvegicus) 210.0 84.0 3.2:1 103.0 26.0 13.0 5732 2–5

aElephant (Loxodonta

africana africana)

176.9 47.3 0.61:1 60.7 38.8 7.0 3975 100–260

aRhinoceros (Ceratotherium

simum)

77.5 16.2 0.22:1 7.4 61.0 3.0 1589 25–35

Source: Modified from Uniacke et al. 2010.

Values are expressed asag.kg−^1 orbg.L−^1 Milk.

catalase, lipase and proteinase. Figure 26.1 shows the affect of

lactation on the main constituents of equine milk and indicates

a very rapid transition from equine colostrum to mature equine

milk, that is within the first 24 hours of lactation. The concen-

tration of protein in equine milk is very high,>15 g/100 g milk,

immediately post-partum, but decreases rapidly to<4 g/100 g

milk after 24 hours of lactation and to less than 2 g/100 g milk

after 4 weeks of lactation (Fig. 26.1A). The casein to whey pro-

tein ratio in equine colostrum is 0.2:1 immediately post-partum

and this changes to approximately 1.1:1 within 1 week. The pro-

tein content of bovine milk decreases during the first 3 months

of lactation, but increases subsequently (Walstra et al. 2006a).

The concentration of lactose in equine more than doubles dur-

ing the first 24 hours (Fig. 26.1C), and this is also observed for

bovine milk (Walstra et al. 2006a). The concentration of lactose

in equine milk subsequently increases steadily throughout fur-

ther lactation (Fig. 26.1C), a trend that is different from that for

bovine milk in which lactose content decreases progressively

(Walstra et al. 2006a). Close agreement is observed between

the data of various studies for the level of protein (Fig. 26.1A)

and lactose (Fig. 26.1C) in equine milk but considerable differ-

ences are reported for the lipid content of equine milk between

different studies (Csapo et al. 1995, Doreau et al. 1986). This ́

may be due to an increase in the fat content of equine milk that

occurs during a milking session and, in some cases, the use of

the hormone, oxytocin, which promotes complete evacuation

of the udder (Doreau et al. 1986). Hence, the volume of milk

drawn and the degree of evacuation of the udder will signifi-

cantly influence the lipid content of the milk and thus explain

differences in lipid content observed between different studies.

However, all studies indicated in Figure 26.1B show the same

trend, that is a decrease in the lipid content of equine milk with