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2 d before the start of the supplementation treatments, average milk production for
supplementation treatments within each stage of lactation was similar (P > 0.10). In the analyses
of test day milk yield, milk fat percentage and milk protein percentage, none of the two-way or
three-way interactions were statistically significant. Therefore, the least squares means within
test days for these three traits by the main effects of stage of lactation and supplementation
treatment are plotted in Figures 2, 3 and 4, respectively. Least squares means, averaged over test
days, are presented in Table 2.
Figure 1: Average test day milk production for stage of lactation and supplementation
treatment combinations.
Milk (kg/d)
3
2.5
2
1.5
1
0.5
0
-2 5 12 19 26 33 40 47 54 61 68 75 82
Day of trial
60
Early lactation - Supplemented
Early lactation - Unsupplemented
Late lactation - Supplemented
Late lactation - Unsupplemented
On each test day during the trial, early lactation ewes produced more milk than late lactation
ewes and supplemented ewes produced more milk than unsupplemented ewes (Figure 2);
however, none of the differences within a test day were statistically significant. When these
differences were averaged across test days, large and significant differences were observed
between stage of lactation and between supplementation treatments (Table 2). Early lactation
ewes produced more (P < 0.0001) daily milk (+ 0.53 kg), FCM (+ 0.36 kg), and FPCM (+ 0.34
kg) than late lactation ewes. Since milk production generally peaks in the fourth week of
lactation and then slowly declines (Carta et al., 1995), the early lactation ewes are expected to
have greater daily milk yield than late lactation ewes.
Supplemented ewes produced more (P < 0.01) daily milk (+ 0.23 kg), FCM (+ 0.16 kg), and
FPCM (+ 0.14 kg) than unsupplemented ewes (Table 2). This supports previous work in which
supplementation increased milk production in lactating ewes (D’Urso et al., 1993). However, it
is somewhat surprising that the response to supplementation was similar in ewes at both stages of
lactation. Cannas (2002) suggests that supplementation in late lactation may contribute more to
an increase in body weight than milk production. Changes in body weight (Figure 5) somewhat
support this theory, but milk production also was positively affected by supplementation in late
lactation ewes.