Dairy Sheep Symposium - the Department of Animal Sciences ...

Management factors affecting the quality of sheep milk
In Figure 2 it was shown how the farmer has control over the management of the flock of
dairy ewes and that some management practices can affect the quality of sheep milk.
Milking techniques
In most Mediterranean countries sheep are still hand-milked with the consequence of poor
hygiene and high bacterial counts and somatic cell counts in the milk (Gall 1975; Fatouros 1986;
Anifantakis 1990). However, the concentration of protein and fat in the milk does not differ
between hand and machine milked ewes (Casu et al. 1978a).
In Australia and New Zealand sheep are milked by machine and the milk has better microbiological
characteristics.
The machine milking of sheep has been reviewed by Purroy Unanua (1996). The design of
milking parlours and the organization of the milking operations have been described by Enne
(1976) and Pazzona (1980) in Italian and by Kervina et al. (1981), Mills (1989), Gilbert (1992a)
and Dawe (1992) in English. The practical recommendations of Gilbert (1992a) and Dawe
(1992) are particularly relevant to the emerging sheep milking industries of Australia and New
Zealand.
Interval between milkings and frequency of milking
Wilde and colleagues (Wilde et al. 1987a; 1987b; 1988; Prentice et al. 1989; Wilde et al.
1989; Hillerton et al. 1990; Wilde and Knight 1990; Wilde and Peaker 1990, Wilde et al. 1996)
have established that the rate of milk secretion is controlled locally by the Factor Inhibiting
lactation (FIL), a fraction of the whey proteins present in milk. As a consequence, the interval
and frequency of milking assume a paramount importance in affecting the yield of milk. The
findings of Denamur and Martinet (1961) and Grigorov and Shalichev (1962) provided some
indirect evidence that an autocrine control of milk secretion is present in sheep. This was later
confirmed by Bencini (1993) and McFerran (1996). Therefore the interval between milking, the
milking frequency and the adoption of stripping methods to remove additional milk and ensure
completeness of milking increase both the daily output of milk and the total lactation yield of
dairy ewes by removing the inhibitory effect of milk accumulated in the alveolar tissue of the
mammary glands.
In the dairy cow, increasing the frequency of milking increases milk production (Porter et al.
1966; Pelissier et al. 1978; Phillips et al. 1980; Waterman et al. 1983; Rao and Ludri 1984;
Amos et al. 1985; Gisi et al. 1986; Barnes et al. 1990; Hillerton et al. 1990), but milking at
different intervals does not change the yield of milk (Elliott 1959) because the rate of milk
secretion does not change for the first 16-20 hours after milking (Turner 1953; 1955; Elliott and
Brumby 1955; Elliott 1959; Porter et al. 1966; Bartsch et al. 1981; Van Trinh and Ludri 1984).
Changing the frequency of milking or the milking interval also does not affect the composition
of the milk (Rao and Ludri 1984; Amos et al. 1985; Hillerton et al. 1990).
In dairy sheep, several authors have reported that reducing the frequency of milking results
in a loss in milk production (Morag 1968; Casu and Labussière 1972; Labussière et al. 1974;
Geenty and Davison 1982; Papachristoforou et al. 1982; Purroy Unanua 1986) and increasing
the frequency of milking increases milk production (Morag 1968; Karam et al. 1971; Bencini
1993), but there are few and contrasting reports on the effect of milking frequency and interval
on the composition of the milk. Casu and Labussière (1972) and Huidobro (1989) reported that