¨ 112
S . Østergaard, Y.T. Grohn Livestock Production Science 65 2000 107 –118
1999 regarding disease interrelationships within neous. The variation in repeated measures within
these same 12 years of data. cows was accounted for by multiplying the error
2
We used the PQL procedure Breslow and variance s by the covariance matrix R, which was
e
Clayton, 1992 implemented in the SAS macro assumed to have first-order autoregressive covar-
GLIMMIX Littell et al., 1998 version GLMM iance.
6.12 last updated 5th December 1997 to fit the Each model included several fixed effects, includ-
models. Model selection was based on a backwards- ing those for herd, breed, and season as in model 1.
elimination strategy, using the F-statistic as the Parity was only in the multiparous cow models of
criterion at
P ,0.05 two-tailed.
Because we
total DMI two categories according to parity 2 and thought that parity would be a significant effector of
. 2 and the models of total concentrate DMI two
disease incidence, parity was forced to remain within categories according to parity 1, 2, and .2. Stage
all models. of lactation included nine categories according to
week of lactation 0, 1, 2, 3–4, 5–6, 7–9, 10–13, 14–18, and 19–24. The indicator variable to de-
2.4. Statistical analyses: effects of disorders on scribe week of lactation, relative to the week of
DMI diagnosis of the disorder also had nine categories.
Category 0 represented cows free of the disorder. The analyses of the effects of disorders on total
The other eight categories were for cows with the DMI were carried out separately for primiparous and
metabolic disorder, and indicated whether that week multiparous cows, because of differences in shapes
of data was from before 24, 23, 22, 21 or of the feed intake capacity curves and because there
after 11, 12, 13, 4 the week of diagnosis. The were parity-specific differences in median DIM at
day of diagnosis was the first day of week 11 in this ¨
diagnosis Østergaard and Grohn, 1999. However, coding.
the analyses of the effect of disorders on total To fit model 2 we used the SAS MIXED pro-
concentrate DMI were not carried out separately for cedure from SAS Institute 1996 with the restricted
primiparous and multiparous cows. This was because maximum-likelihood method. Model selection pro-
of concentrates being fed restrictively and separately, cedures were as already presented for the modelling
consequently, smaller
parity-specific differences
of the odds of disorders model 1. occurred in total concentrate DMI. Separate analyses
of separately fed concentrate DMI, primiparous total DMI and multiparous total DMI for each of the four
3. Results
metabolic disorders, resulted in 12 analyses. The ‘effects’ of disorders on weekly DMI were tested in
The first diagnoses of each of the four disorders these analyses by this repeated-measures ANOVA
are summarised in Table 2; overall, at least one of model:
the four disorders was recorded for 23 of the cows y 5 Xb 1 Zg 1 e
Model 2 and 14 of the lactations. For results of disease
Where y is a vector representing the response interrelationships, reference is made to the study of
¨ variable of DMI. b is a vector of fixed effects. As in
Østergaard and Grohn 1999 on the same data. model 1, g is an unknown vector of random effects
2 2
distributed N0, Is . The s is the variance of 3.1. Odds of disorders
g g
the effects of treatment group nested within trial. In this way, we accounted for the effects of the trials, in
The numbers of lactations in the three data subsets which lactations were used in these research herds
were 498, 1282, and 2861 for concentrates mainly and for the clustering of lactations by trial and by
fed separately, concentrate DMI to total DMI ratio in treatment group within trial. e is an unknown random
the TMR, and percent of all concentrates fed with
2
error vector distributed N0, Rs , whose elements roughages, respectively Table 3. The exclusion of
e
are not required to be independent and homoge- lactations with the study disease before 14 DIM
¨ S
. Østergaard, Y.T. Grohn Livestock Production Science 65 2000 107 –118 113
caused minor reductions in these numbers, in some not related significantly to tercile of percentage of
analyses with model 1. The number of metabolic total concentrate DMI fed with roughages Table 5.
disorder incidents were so low ,8 for three analyses with model 1, that we excluded them. These
3.2. Effects of disorders on DMI analyses were the analysis of decreased rumen
motility based on subset 1 and the two analyses of The fixed effects of herd and season were removed
LDA based on subset 1 and 2, respectively. from the models to solve convergence problems.
The estimated effects of total concentrate DMI, Furthermore, the covariance parameters in some
analysed for cows fed all concentrates separately models were estimated using minimum-variance
subset 1, are shown in Table 4. The risk of enteritis quadratic unbiased estimation MIVQUE0 SAS
was increased significantly i.e. where the confidence Institute, 1996.
interval did not included 1.0 by lower tercile of total Decreased rumen motility 11 cases, enteritis 38
concentrate DMI fed separately Table 4. The odds cases and LDA five cases had no effects on the
of ketosis were not related significantly to total DMI of concentrates fed separately from roughages
concentrate DMI fed separately Table 4. subset 4 within the weeks before and after diag-
The concentrate DMI to total DMI terciles for nosis. Ketosis 82 cases had a significant effect on
cows fed TMR subset 2 were not related sig- the DMI of concentrates 20.4 kg day; S.E.50.2
nificantly to the odds of any disease studied. The only for the week immediately preceding the diag-
thresholds dividing the terciles of the concentrate nosis the week coded as 21.
DMI to total DMI ratio for cows fed TMR subset 2 In contrast, the four metabolic disorders had many
were 0.44 and 0.51. There were 14, 10 and 19 effects on total DMI subset 5 both before and after
incidents of decreased rumen motility, enteritis, and diagnosis and in both primiparous Table 6 and
ketosis for these analyses. multiparous Table 7 cows. Only enteritis in
The estimated effects of percentage of concentrate primiparous cows and ketosis in multiparous cows
DMI fed with roughages subset 3 are shown in had ‘effects’ decreases in DMI evident earlier than
Table 5. The odds of enteritis and ketosis were 3 weeks before diagnosis, although all disorders was
significantly higher for lower terciles of percentage associated with decreased DMI at least once in
of concentrate DMI fed with roughages Table 5. weeks 23, 22, or 21. All disorders had detrimental
The odds of decreased rumen motility and LDA were effects lower DMI in weeks 11 and 12, and all
Table 4
a
Effect of total concentrate DMI on adjusted odds ratios of metabolic disorders Metabolic
Number of Tercile of total
Odds ratio
b
disorder concentrate DMI
and 95 confidence interval Lactations
Disorders OR
95 CI OR
c
Enteritis 495
22 Lowest vs. middle
1.7 [0.8; 3.6]
Lowest vs. highest 10.0
[2.9; 35.2] Middle vs. highest
5.8 [1.8; 18.8]
c,d
Ketosis 494
48 Lowest vs. middle
1.5 [0.7; 3.2]
Lowest vs. highest 1.0
[0.4; 2.2] Middle vs. highest
0.7 [0.3; 1.5]
a
Estimated by model 1 on data subset 1, which includes cows fed concentrates separately from roughages. Only diseases with significant effect are included.
b
Lowest, middle and highest terciles kg day: lowest: ,5.2; middle: 5.2 and ,6.6; highest: 6.6.
c
Herd retained in the final model.
d
Milk fever retained in the final model.
¨ 114
S . Østergaard, Y.T. Grohn Livestock Production Science 65 2000 107 –118
Table 5
a
Effect of percentage of total concentrate DMI fed with roughages on adjusted odds ratios of metabolic disorders Metabolic
Number of Tercile of percentage of total
Odds ratio disorder
concentrate DMI fed with and 95 confidence interval
Lactations Disorders
b
roughages OR
95 CI OR Decreased rumen
2840 52
Lowest vs. middle 1.8
[1.1; 2.9]
c
motility Lowest vs. highest
1.2 [0.6; 2.4]
Middle vs. highest 0.7
[0.3; 1.4] Enteritis
2822 96
Lowest vs. middle 1.2
[0.8; 1.7] Lowest vs. highest
4.5 [2.3; 8.7]
Middle vs. highest 3.9
[2.0; 7.7]
d
Ketosis 2832
126 Lowest vs. middle
2.1 [1.4; 3.2]
Lowest vs. highest 3.9
[2.2; 3.7] Middle vs. highest
1.8 [1.0; 3.3]
Left displaced 2861
12 Lowest vs. middle
0.7 [0.2; 2.7]
e
abomasum Lowest vs. highest
1.3 [0.3; 5.4]
Middle vs. highest 2.0
[0.5; 8.1]
a
Estimated by model 1 on data subset 3, which includes cows that did not have access to summer pasture. Only diseases with significant effect are included.
b
Lowest, middle and highest terciles ratio: lowest: ,0.32; middle: 0.32 and ,1.0; highest: 1.0.
c
Milk fever retained in the final model.
d
Acute clinical mastitis and clinical mastitis evident only as flakes in the milk retained in the final model.
e
Due to few disease incidents, parity was excluded from this model. Table 6
Effects of study diseases on kg total DMI in weeks around the day of diagnosis in primiparous cows final mixed models 34679 observations from 1698 lactations in three Danish dairy-research herds, 1985 to 1997
a
Week relative to Study disease
date of diagnosis
b
Decreased rumen Enteritis
Ketosis LDA
motility n 540 n 572
n 539 n 56
b S.E.
b S.E.
b S.E.
b S.E.
2 4
2 0.1
0.3 2
0.5 0.2
2 0.5
0.3 0.3
1.0 2
3 0.1
0.4 2
0.5 0.3
2 0.5
0.3 0.4
0.9 2
2 0.0
0.4 2
0.4 0.3
2 0.7
0.3 2
3.1 0.8
2 1
2 2.0
0.3 2
2.0 0.3
2 2.7
0.3 2
5.5 0.8
1 1
2 1.8
0.3 2
1.6 0.3
2 1.5
0.3 2
3.4 0.8
1 2
2 1.1
0.3 2
0.5 0.2
2 1.0
0.3 2
2.4 0.7
1 3
2 0.7
0.3 0.5
0.2 2
0.7 0.3
2 2.3
0.7 1
4 2
0.4 0.2
0.5 0.2
2 0.6
0.2 2
1.6 0.6
a
Intercept based on the period between the 19th to 24th weeks in milk for primiparous not Jersey cows without the study disease.
b
Covariance parameters were estimated using minimum variance quadratic unbiased estimation MIVQUE0 as explained in the text. P ,0.05, P ,0.01, P ,0.001.
disorders except enteritis in multiparous cows also lactation was 13.5 kg day S.E.50.2 for primipar-
‘caused’ decreased DMI in week 13. The losses ous Jersey cows without ketosis; the effect on DMI
continued for more than 3 weeks after diagnosis in of other breeds same circumstances was 13.3 kg
cow with ketosis and in primiparous cows with LDA. day S.E.50.1. Analogous values for multiparous
The estimated total DMI during weeks 19–24 of cows were 15.6 kg day S.E.50.3 and 14.5 kg
¨ S
. Østergaard, Y.T. Grohn Livestock Production Science 65 2000 107 –118 115
Table 7 Effects of study diseases on kg total DMI in weeks around the day of diagnosis in multiparous cows final mixed models 38743
observations from 1975 lactations in three Danish dairy-research herds, 1985 to 1997
a
Week relative to Study disease
date of diagnosis Decreased rumen
Enteritis Ketosis
LDA
b
motility n 584 n 5127
n 5208 n 522
b S.E.
b S.E.
b S.E.
b S.E.
2 4
2 0.6
0.3 2
0.1 0.3
2 0.7
0.3 2
1.1 0.9
2 3
2 0.5
0.4 0.0
0.3 2
0.8 0.2
2 1.5
0.8 2
2 2
0.9 0.4
2 0.1
0.3 2
0.9 0.2
2 2.4
0.7 2
1 2
3.8 0.4
2 2.0
0.3 2
2.8 0.2
2 6.6
0.7 1
1 2
2.9 0.4
2 1.9
0.3 2
2.1 0.2
2 6.6
0.7 1
2 2
1.9 0.3
2 0.9
0.3 2
1.4 0.2
2 4.2
0.6 1
3 2
0.8 0.3
2 0.4
0.2 2
1.0 0.2
2 1.2
0.6 1
4 2
0.2 0.3
0.0 0.2
2 0.7
0.2 2
0.1 0.4
a
Intercept based on the period between the 19th to 24th weeks in milk for multiparous not Jersey cows without the study disease.
b
Covariance parameters were estimated using minimum variance quadratic unbiased estimation MIVQUE0 as explained in the text. P ,0.05, P ,0.01, P ,0.001.
day S.E.50.2, respectively. These values differed concentrates separately from roughages subset 3
only slightly in the models of the effects of the other and not the concentrate to roughage ratio within a
three disorders. TMR subset 2 — that is associated with increased
odds of metabolic disorders. The results from the analyses of the effect of concentrate DMI for cows
4. Discussion fed all concentrates separately subset 1 are ex-
