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

Individual ewe milk production (morning, evening, and/or afternoon) was recorded and morning
milk samples were collected every 2 wk throughout the experiment. Milk composition analyses
for percentage of fat and protein, and Fossomatic somatic cell count (SCC) were performed by a
State of Wisconsin certified laboratory. Parlor time (the time for entry, machine milking, and
parlor exit) was recorded every other day with a stopwatch during the morning milking for each
treatment group of 24 ewes. Adjusted 24-h milk production was calculated on each test day by
adding the 0600 and 1800 production for the 12H ewes, and by adding the 0600, 2200, and 1400
production and then dividing by two, for the 16H ewes. An estimation of total milk production,
percentages of milk fat and protein, and total milk fat and protein yield for the 90-d experimental
period was calculated according to Thomas et al. (2000). SCC was transformed to logarithms of
base ten and averaged over the 90-d experiment. Ewes were removed from the experiment and
dried-off when their daily milk production on a test day fell below 0.4 kg/d.
Least squares means analysis of variance was conducted with the general linear models
procedure of SAS (1999). The experimental design was a split plot on time for measurements
taken every 15 d (Figure 1). The model included the main plot effects of: treatment (12H or
16H) and ewe within treatment; and the sub-plot effects of: day (d-90, 105, 120, 135, 150, 165,
and 180), treatment x day, and residual error. Least squares means for treatment were tested
against ewe within treatment as the error term; treatment x day interaction was tested against
residual error. For data presented in Table 1, a simple one-way ANOVA was used to estimate the
effect of treatment.
Results
During the experimental period (d 90 to the end of lactation), 16H ewes were machine
milked 45 fewer times than 12H ewes (Table 1), and most lactation traits did not differ between
treatments. Ewes milked every 12 h compared to ewes milked every 16 h during mid- to latelactation
had similar lactation length (178.4 d), milk production (118.5 kg), milk fat percentage
and yield (5.50% and 6.3 kg, respectively), milk protein percentage and yield (4.78% and 5.5 kg,
respectively), and SCC (4.67 log units) (Table 1). Throughout the experiment 16H ewes had
similar adjusted 24-h milk yield compared to 12H ewes (Figure 1), however, morning milk yield
was 28% higher (P < 0.01) for 16H vs. 12H ewes (Table 1 and Figure 1).
Discussion
The results of the present experiment demonstrate a clear advantage in milking efficiency for
East Friesian dairy ewes managed with a milking interval of 16 h during mid- to late-lactation
(last 90 d of a 180 d lactation), because there is a 25% reduction in the number of milkings, yet
no compromise in milk yield, milk composition, or lactation length, compared to ewes managed
with the normal 12-h milking interval. Most reports concerning the effect of once-daily milking
in ewes have shown significant losses in milk production and hypothesize that lactation length
would also be reduced (Casu and Labussière, 1972; Knight and Gosling, 1994; Morag, 1968).
Apparently, a 16-h milking is more appropriate for dairy ewes, compared to a 24-h milking
interval, because we observed no detrimental effect on lactation traits. Moreover, a 25% reduction
in total labor was realized with the 16-h milking interval, which permits dairy sheep producers
more time to devote to other farming practices and/or to other activities off the farm.
Had the experiment been conducted during early lactation, it is likely that less frequent
milking would have significantly reduced lactation performance of these East Friesian dairy
ewes. Less frequent milking during early lactation results in reduced milk yield in dairy cows