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S . Østergaard, Y.T. Grohn Livestock Production Science 65 2000 107 –118
roughage ratio in the feeds given to the cows. Energy complex into analyses of some underlying mecha-
is the nutrient for which intake is most closely nisms. Within homogenous feeding management
related to the level of milk production Bath, 1985 types, various feeding measures may be defined
and is, consequently, widely used in systems for independently of feed intake, such as the concentrate
predicting milk production Kaustell et al., 1997 to roughage ratio for cows fed a TMR. In this study,
and in relation to profitability in dairy herds Van- such measures were defined to be studied as potential
dehaar, 1998. Decisions relating to concentrate risk factors for diseases. By supplementing such
feeding also might affect metabolic and presumed analysis with an estimation of feed intake as a
feeding-related disorders Veenhuizen et al., 1991; disease specific function of day of diagnosis may
Geishauser, 1995; Gustafsson et al., 1995; Shaver, explain some of the ‘feeding–health’ complex. Con-
1997. Since, significant economic loss may be sequently, we addressed such analyses for decreased
associated with incidence of metabolic disorders rumen motility, enteritis, ketosis, and left-displaced
Kossaibati and Esslemont, 1997, the relationship abomasum LDA.
between feeding and diseases may be important for The purposes of this study were 1 to test
the production in a dairy herd. Unfortunately, the whether odds of metabolic disorders varied accord-
relationships between feeding of concentrates and ing to concentrate management in the early lactation,
metabolic disorders are poorly quantified — pre- and 2 to test whether metabolic disorders were
sumably because of the lack of detailed recording related to either DMI of concentrates fed separately
from the individual cow Østergaard and Sørensen, from roughages or total DMI, both, in the three
1998. weeks before and the 3 weeks after the clinical
Cows on the same diet including roughages ad diagnosis was made.
libitum, may differ in concentrate DMI and in concentrate to roughage ratio, due to variations in
feed preference, intake capacity, and presentation of
2. Materials and methods
concentrates such as separately or mixed with roughage. Also, associations between concentrate
2.1. The herds and lactations DMI and roughage DMI and metabolic disorders,
might vary according to when the DMIs are mea- Data for this retrospective study originate from
sured in relationship to the date of diagnosis. These three research herds of the Danish Institute of
facts call for data with frequently recorded feed Agricultural Sciences, Denmark, between April 1985
intake for each individual cow, which is very costly and August 1997 The breeds and parities are shown
to fulfil simultaneously with the demand for many in Table 1. Except during the periods where cows
observations on cows due to the relatively low had access to summer pasture two herds, the
incidence of feeding related diseases. However, these milking herds were kept in tie stalls. Feedstuffs
demands have been fulfilled in the data available for offered and refused except pasture were measured
this study. These data have been recorded during 12 daily for each cow. Because ration analyses were
years in three Danish research herds. These herds available, it was possible to calculate weekly or
had records on weekly or bi-weekly individual-cow bi-weekly, the total concentrate and roughage DMIs
DMIs for all concentrates and most roughages for each cow for at least 168 days in milk DIM.
exception: summer pasture in two herds, on the Throughout this study we used feed intake measures
manner of feeding the concentrates within a total i.e. what the cows actually eat as opposed to
mixed ration
TMR, entirely
separate from
measures of what the cows were offered. Hay, straw roughage, or partly separate from roughage, and on
and feedstuffs with dry matter , 70 was defined to diagnoses of clinical disorders.
be roughages. Other feedstuffs were defined to be The fact that an analysis of the effect of feeding
concentrates. It was also possible to identify the DMI on disease should control for feeding management
of concentrates fed separately from roughages rather and feed intake as a disease specific function of day
than fed, e.g. within a TMR and of roughages of diagnosis made us split-up the study of the
except pasture fed separately from concentrates. If
¨ S
. Østergaard, Y.T. Grohn Livestock Production Science 65 2000 107 –118 109
Table 1 Number of lactations by herd, breed, and parity 1856 total cows with 3676 total lactations, three Danish dairy-research herds, 1985 to 1997
Breed Parity
Number of lactations Herd I
Herd II Herd III
Total Danish black and white
1 224
762 184
1170 2
101 533
131 765
. 2
54 623
158 835
Danish jersey 1
136 –
– 136
2 46
– –
46 .
2 23
– –
23 Danish red
1 232
50 –
282 2
81 39
– 120
. 2
31 29
– 60
Danish red and white 1
14 –
– 14
2 11
– –
11 Crossbreed dairy cows
1 –
95 1
96 2
– 71
– 71
. 2
– 47
– 47
All breeds All
953 2249
474 3676
roughages and concentrates were only fed separately, The order in which the diagnoses are mentioned
the general strategy was to feed roughages ad above indicates this ranking.
libitum, whereas concentrates were fed as a set We chose not to study milk fever because it occurs
amount regardless of test-day milk yields of the so soon after parturition that post-parturient feeding
individual cow. our interest could not logically be a risk factor.
A uniform procedure of making a diagnosis was Only four right-displaced abomasa were recorded,
used in all of the three herds. All diseases were consequently, we could not investigate that disorder.
diagnosed and treated by a veterinarian. The cows Cows were typically being used in various trials
were not routinely vetted. If the stockmen noted while the data we used was being recorded. If cows
something wrong, then a veterinarian was sent for. were assigned to trials unlikely to affect feeding and
At each disease case, a single diagnosis was made metabolic disorders, we did not take it into account
and recorded by the veterinarian, according to a e.g. trials of milking management or of animal
standard protocol of disease diagnoses. handling. Most cows were only on a single herd
The LDA diagnosis was entrapment of the en- trial between parturition and 168 DIM. In all cases
larged fluid- or gas-filled abomasum high in the left we only accounted for the initially-assigned trial in
abdominal cavity. Ketosis was diagnosed by using any lactation in our study. If a cow was not assigned
clinical signs combined with a test on a milk sample. to a trial before 168 DIM, a dummy value specific
Enteritis was diagnosed primarily by the presence of for the herd-year was used. In total, the lactations we
diarrhoea, which in some cases could be bloody. used and trials which we accounted for included 71
Cows with enteritis were typically feverish. De- trials and 230 treatment groups.
creased rumen motility was diagnosed if rumen contractions were considered significantly reduced.
2.2. Data exclusions and subsets of the data Cows with decreased rumen motility were typically
not feverish. Data from fistulated, intensively managed cows
Some of the clinical signs related to these diag- were excluded. Data from weeks where cows had
noses could be related to more than a single diag- access to summer pasture were excluded from any
nosis. Generally, those relatively less well-defined analyses that required measures of roughage DMI.
diagnoses were made only if a better-defined diag- Data were used only from the first 168 DIM, for
nosis could not be made, based on the clinical signs. three reasons. Firstly, as stated above, most lacta-
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S . Østergaard, Y.T. Grohn Livestock Production Science 65 2000 107 –118
tions were involved in only a single trial before 168 all of the total DMI was fed between parturition and
DIM. Secondly, the disorders we studied were 42 DIM as a TMR and in which the cow did not
diagnosed primarily in early or mid-lactation. Third- have access to summer pasture early on in that
ly, when concentrates and roughages were fed separ- lactation. This subset of the data was used to study
ately, the feeding plan for concentrates tended not to whether the odds of metabolic disorders varied
be based on milk yield until at least 168 DIM had according to concentrate DMI to total DMI ratio.
been reached. Diagnoses made earlier than 14 DIM The third subset of the data included the lactations in
were excluded from analyses in which the aspects of which the cow did not have access to summer
feeding were risk factors, as opposed to outcomes, pasture between parturition and 42 DIM. This subset
because we felt that post-partum feeding was unlike- of the data was used to study whether the odds of
ly to be a major risk factor for disorders occurring so metabolic disorders varied according to the per-
soon after calving. Finally, lactations were excluded centage of the total concentrate DMI that was fed
if the data were not available for most of the weeks with
roughages [concentrate
DMI fed
with between parturition and 168 DIM. The 3676 lacta-
roughages 4 total concentrate DMI 3 100]. In tions remaining after these exclusions are described
this way, it was possible to compare cows fed TMR in Table 1 and the disease diagnoses are described in
with those fed some or all concentrates separately Table 2.
from the roughages. To study whether the odds of disease varied
In addition, a fourth and a fifth subset of the data, according to post-partum feeding, three subsets of
based on feeding management, was created to ex- the data were created, based on feeding management.
plore the effects of each metabolic disorder on week- The first subset of the data included only lactations
specific feed intake. The fourth subset of the data in which all of the concentrates fed between parturi-
included only lactations in which . 90 of concen- tion
and 42
DIM were
fed separately
from trates fed between parturition and 168 DIM were fed
roughages. This subset of the data was used to study separately from roughages. This subset of the data
whether the odds of metabolic disorders varied was used to explore the effects of each metabolic
according to total DMI of concentrates. The second disorder on week-specific concentrate DMI fed
subset of the data included only lactations in which separately from roughages. The fifth subset of the
Table 2 Frequency, lactational incidence and DIM for the first diagnoses of each study disease: data include 1698, 1013, and 965 lactations ,168
DIM from parities 1, 2, and .2, respectively 3 Danish dairy-research herds, 1985 to 1997 Study diseases
a
Decreased Enteritis
Ketosis LDA
rumen motility Frequency
Parity 1 40
72 39
6 Parity 2
24 54
80 10
Parity .2 60
73 128
12 Total
124 199
247 28
Lactational incidence Parity 1
2.4 4.2
2.3 0.4
Parity 2 2.4
5.3 7.9
1.0 Parity .2
6.2 7.6
13.3 1.2
Total 3.4
5.4 6.7
0.8 DIM at diagnosis
Median 25
22 25
17
b
SIR 10
31 10
8
a
LDA, left-displaced abomasum.
b
Semi-interquartile range is calculated as the half of the range between the 3rd and the 1st quartile of DIM.
¨ S
. Østergaard, Y.T. Grohn Livestock Production Science 65 2000 107 –118 111
data included only data from weeks in which they and for the clustering of lactations by trial and by
did not have access to summer pasture. This subset treatment group within trial.
of the data was used to explore the effect of each Because there were four disorders and three
metabolic disorder on week-specific total DMI. ‘types’ of feeding management, defining the first,
The definition of the created subsets of the data second, and third subset of the data Table 3, the
are summarised in Table 3, along with a clarification model was used for 12 different analyses. Within
of the specific analyses that the data were applied to. each of the three subsets of the data, each lactation’s
According to the criteria for each subset of the data, mean value, between parturition and 42 DIM for the
each lactation may be included in one or more subset’s defining feeding characteristic, was calcu-
subsets. lated. These mean values were then used to define
the lactation as being within the lowest, middle, or highest tercile for the feeding characteristic. The
2.3. Statistical analyses: odds of disorders specific comparisons were lowest to middle tercile,
lowest to highest, and middle to highest. Odds ratios The odds of disorders diagnosed between 14 and
OR and 95 confidence intervals were calculated 168 DIM according to feeding characteristics were
from the models. explored using this generalised linear mixed-model
The specific fixed effects b offered to each GLMM analysis for binomial data:
model, in addition to tercile of the feeding charac- teristic, were herd three categories; not random
logit p 5 Xb 1 Zg 1 e Model 1
because there
were only
three, breed
two categories; Jersey and not Jersey, calving season
Where, p is a vector representing the response on a four categories, each of three months; winter5
logit scale ‘ln p 1 2 p’ of the expected chance to December–February, parity three categories ac-
contract the metabolic disorder under study. b is a cording to parity 1, 2, and .2, and interaction
vector of fixed effects being analyses as risk factors. between parity and tercile of the feeding characteris-
g is an unknown vector of random effects distributed tic nine categories. Also, depending on the specific
2 2
N0, Is , in which s was the variance of the disorder being modelled, other ‘risk-factor’ disorders
effects of treatment group nested within trial. In this yes no for each such risk factor were offered to the
way, we accounted for the effects of the trials in model as fixed effects; these decisions were based
¨ which lactations were used in these research herds
mainly on the findings of Østergaard and Grohn
Table 3 Definition of the created subsets of the data and for which analyses each of them is used
Subset Criterion for including records
Number of Number of
Analysis number
lactations weekly recordings
1 All of the concentrates fed 0 to
498 Aggregated measure
Effect of total concentrate 42 DIM were fed separately
per lactation used DMI on disease
from roughages 2
All of the total DMI was fed as 1282
as above Effect of concentrate
a TMR and no access to summer DMI to total DMI
pasture, both 0 to 42 DIM ratio on disease
3 No access to summer pasture
2864 as above
Effect on disease of percentage 0 to 42 DIM
of the total concentrate DMI that was fed with roughages
4 .
90 of concentrates fed 0 to 664
16 459 Effects of each disease on
168 DIM were fed separately week-specific concentrate DMI
from roughages fed separately from roughages
5 No access to summer pasture
3673 73 422
Effect of each disease on in the current week
week-specific total DMI
¨ 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
