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

during milking, resulting in less efficient milk removal (Bruckmaier, 2001).
Because of traditional or routine farming practices (i.e. milking before and after the work
day), twice-daily milking is most common for domestic dairy ruminants. However, it is possible
that longer milking intervals might be tolerated by some species, such as the dairy ewe and goat,
which have larger cisternal storage capacity (up to 75% of total milk yield, Marnet and
McKusick, 2001) compared to cows (20 to 30%, Bruckmaier, 2001). Increases in milking
frequency would thus only be advantageous for species such as the dairy cow that store the
majority of milk in the alveoli, while decreases in milking frequency would be more advantageous
for the ewe and goat which store relatively more milk within the cistern. In other words
compared to the cow, dairy ewes might not suffer the same degree of loss in milk production or
in lactation length with less frequent milking. Moreover, simplification of the milking routine
would presumably result in significant savings in labor and expenses.
In dairy ewes, little research has been conducted on appropriate milking intervals. Researchers
in France and Sardinia with dairy ewes have tested the effect of omitting one or both of the
Sunday milkings to enable farmers to spend more time with their family and other off-farm
activities; they reported losses of 5 to 25% in milk production (Casu and Labussière, 1972;
Labussière et al., 1974; Labussière, 1988). The effect of consistently longer milking intervals
(i.e. 24 h) on commercial milk production and lactation length is not known. Intermediate to
once- or twice-daily milking, is a milking routine that comprises three milkings in 48 h. However,
there are no reliable reports on 16-h milking intervals in dairy ewes, and only one published
study in dairy cows where yield losses of 7 to 18% were reported (Woolford et al., 1985).
We hypothesize that a milking interval of 16 h would be appropriate for dairy ewes because
of their increased cisternal storage capacity, and the fact that a 16-h time period lends itself to
organization of the milking routine to include three milkings every 48 h (e.g. 0600, 2200, and
1400). The objectives of the present experiment were to estimate the differences in milk production,
milk composition, somatic cell count (SCC), and lactation length for East Friesian dairy
ewes managed with either a 12- or 16-h milking interval from mid- to late-lactation.
Materials and methods
Forty-eight third parity East Friesian crossbred dairy ewes were studied from d 90 to the end
of lactation at the Spooner Agricultural Research Station of the University of Wisconsin-Madison
during the summer of 2001. Ewes with symmetrical udders, similar average daily milk production
(1.8 ± 0.4 kg/ewe, mean ± SD) and stage of lactation (88 ± 7 d, mean ± SD) were chosen
from the main dairy flock of 350 ewes that are normally machine milked twice daily. All ewes in
the experiment had been weaned from their lambs at approximately 24 h post-partum. Ewes
were randomly assigned to two milking frequency treatments for the remainder of lactation:
twice daily machine milking at 0600 and 1800 (12H, n = 24), or three milkings in 48 h at 0600,
2200, and 1400, respectively (16H, n = 24). Treatment groups were housed separately in two
neighboring pens and fed a 16% crude protein concentrate and alfalfa hay.
Machine milking took place in a 2 x 12 high-line Casse system milking parlor with 12 milking
units and two milking technicians. The milking machine (Alfa Laval Agri Inc., Kansas City)
was set to provide 180 pulsations per minute in a 50:50 ratio with a vacuum level of 36 kPa.