136 C
.C. Ketelaar-de Lauwere et al. Livestock Production Science 65 2000 131 –142
into the model as a random effect. In the rotational variables resembles a binomial distribution McCul-
grazing experiment, the observation day was in- lagh and Nelder, 1989
corporated into the model as a fixed effect to A log-linear model with random effects was used
estimate the effect of sward height because sward for the analysis of the distribution of the cows’
height decreased in the course of the observation activities over the barn and the pasture. In that
days. In the strip-grazing experiment, the experimen- model, the total time an activity was performed
tal period was incorporated into the model as a fixed outdoors was assumed to be proportional to the total
effect to estimate the effect of the distance between time the activity was performed. In the rotational
the pasture and the barn because this distance grazing experiment, the observation day was used as
differed between experimental periods. The Wald an explanatory factor representing sward height, and
statistic VWS was calculated to test for a 99 in the strip grazing experiment, the distance between
probability level whether fixed effects were signifi- the pasture and the barn was used as an explanatory
cant under the null hypothesis that there was no factor. In both experiments, the lactation number was
effect. This statistic has an asymptotic chi-squared used as a covariable.
distribution Genstat 5 Committee, 1993. Model To get an impression of possible weather effects, a
selection took place by backward elimination, based relationship was calculated between the black globe
on this Wald statistic. temperature outdoors and the time the cows spent
In general, the model looked as follows: indoors between 10:00 and 17:00 h. It was assumed
that the standard deviation of the response variables increased proportionally to expected response values.
fY 5 A 1 B 1 U 1 e
ijkl ij
k l
ijkl
The distribution of AMS visits over the 24-h period was analysed using a log-linear model. The
24-h period was divided into eight periods of 3 h Y
5observed value of response variable under
ijkl
05:30–08:30 h, 08:30–11:30 h, etc.. The number of consideration for example the number of AMS
AMS visits in a certain period is assumed to be visits of cow l l51 . . . 24 with lactation number k
proportional to the total number of AMS visits. A k 51 or k 2 on day i i 51 . . . 4 in rotational
generalised linear model GLM was fitted instead of grazing experiment and i 51 . . . 5 in strip grazing
a GLMM because differences between observation experiment of experimental period j j 51 . . . 4;
days sward heights were tested per cow over all A 5effect of observation day i sward height on
ij
experimental periods in the rotational grazing experi- experimental period j, or effect of experimental
ment and differences between distances were tested period j distance on day i; B 5effect of lactation
k
per cow over all experimental days in the strip number k; U 5random effect of cow l; e
5residual
l ijkl
grazing experiment McCullagh and Nelder, 1989. error; f 5link function — effects are assumed to be
It was checked whether time intervals between linear on link scale
cows arriving at the AMS followed a negative Response variables monitored by on-line registra-
exponential distribution, because this would indicate tions AMS visits and duration of the cows’ sojourns
that the arrival times were randomly distributed in the pasture, and in the lying, feeding and AMS
Parzen, 1962. areas were analysed according to a linear model. For
The Genstat 5 statistical package was used for all AMS visits, it was assumed that the variance of each
analyses Genstat 5 Committee, 1993. response variable is proportional to the expected
response value. This was confirmed by residual plots. In other cases, it was assumed that the standard
3. Results deviation of the response variables is proportional to
expected response values. 3.1. Sward height
Monitoring the cows’ time budget during direct behavioural observations resulted in binary response
3.1.1. AMS visits variables. These were analysed according to a logis-
Over the course of each experimental period the tic model, assuming that the distribution of response
C .C. Ketelaar-de Lauwere et al. Livestock Production Science 65 2000 131 –142
137
number of milkings, the number of non-milking 6.3 and from 5.1 to 6.3 when sward height decreased
visits and the total number of AMS visits increased S.E.51.0; VWS
510.6; P,0.05.
df53
as sward height decreased Table 1. The number of failed attachments was not affected by sward height.
The statistical analyses confirmed that on each 3.2. Distance between barn and pasture
observation day, the time intervals between consecu- tive AMS visits were not randomly distributed P ,
3.2.1. AMS visits 0.01. This means that the cows visited the AMS in
The distance between the barn and the pasture did closer succession than could be expected on the basis
not affect the total number of AMS visits, nor the number of milkings, non-milking visits or failed
of an exponential factor alone attachments. The predicted mean of the number of
milkings was 2.8 in each experimental period 3.1.2. The cows’ time budget
S.E.D.50.1; VWS 50.2. The predicted means
df53
Table 2 gives an overview of the cows’ time of the total number of AMS visits ranged from 5.0 to
budget. The time in the AMS area and indoors 5.2 S.E.D.50.2; VWS
51.8, those of the num-
df53
increased in the course of the experimental periods ber of non-milking visits from 2.6 to 2.8 S.E.D.5
as sward height decreased and the time in the pasture 0.2; VWS
51.7 and those of the number of
df53
decreased. The data of the direct behavioural data failed attachments from 1.2 to 1.7 S.E.D.50.2;
showed that in the two experimental periods where VWS
510.0. It was confirmed by the statistical
df53
these behavioural observations were carried out, the analyses that the time intervals between consecutive
predicted means of the percentage of time that the AMS visits were not randomly distributed P ,0.01,
cows spent at the feeding gate increased from 5.4 to meaning that the cows visited the AMS in closer
Table 1
e
Predicted means of the number of AMS visits in rotational grazing Day 1
Day 2 Day 3
Day 4 S.E.D.
VWS
df53 a
a b
b
Milkings 2.6
2.7 2.9
3.0 0.1
24.1
a a
b c
Non-milking visits 2.0
2.5 3.4
4.6 0.3
73.0
a a
a a
Failed attachments 1.4
1.5 1.5
1.2 0.3
2.4
d a
a b
c
Total no. of AMS visits 4.4
4.6 5.9
7.3 0.3
115.3
a,b,c
Different superscripts in a row indicate a significant difference between days P ,0.01.
d
Excluding failed attachments because these reflect the ‘behaviour’ of the milking robot instead of that of the cows.
e
Sward height decreased from day 1 to 4; standard error of difference S.E.D. is mentioned as indication of deviation.
Table 2
d
Predicted means of the cows’ time budget in the rotational grazing experiment based on on-line computer registrations 434 24-h periods Time spent min
Day 1 day 2
day 3 day 4
S.E.D. VWS
df53
per cow per day:
a a
b b
In lying area 500.7
512.5 563.5
553.3 14.7
26.0 In feeding area
152.1 147.6
167.9 164.6
11.3 4.5
a a
b b
In AMS area 34.0
33.1 38.6
39.1 1.7
20.3
a b
c c
Indoors 684.0
719.8 796.0
784.2 10.1
170.9
c b
a a
Outdoors 755.2
719.8 643.7
653.8 10.7
147.2
a,b,c
Different superscripts in a row indicate a significant difference between days P ,0.01.
d
Sward height decreased from day 1 to 4; standard error of difference S.E.D. is mentioned as indication of deviation.
138 C
.C. Ketelaar-de Lauwere et al. Livestock Production Science 65 2000 131 –142
succession than could be expected on the basis of an gate were 5.1 when the cows were on a ‘far’ pasture
exponential factor alone. for the first time and 6.2 when they were on a ‘far’
pasture for the second time S.E.51.0; VWS 5
df53
3.2.2. The cows’ time budget 11.9; P ,0.01.
The distance between the barn and the pasture did not affect the time in the lying area Table 3. In the
3.3. Other results second experimental period, when the cows were on
a ‘far’ pasture for the first time, the cows spent less 3.3.1. Distribution of activities over the barn and
time in the feeding area and indoors and more time the pasture
outdoors than in the other experimental periods, When given a choice between being indoors or
when the cows were on ‘near’ pastures or on a ‘far’ outdoors, cows spent most of their time outdoors. If
pasture for the second time Table 3. The time in they could choose between lying indoors or out-
the AMS area was higher in the fourth experimental doors, they mostly lay in the pasture. If they had the
period than in the other experimental periods Table opportunity to eat forage indoors or outdoors, they
3. spent most of the time grazing. This was found in
The data of the direct behavioural observations both experiments.
showed that the predicted means of the percentages In
the rotational
grazing experiment
sward of time spent lying were 41.1 and 39.7 on ‘far’
height, the cows spent between 84.7 and 86.3 of pastures and 47.5 and 44.3 on ‘near’ pastures S.E.5
the 15 h that they could be outdoors at pasture when 1.2; VWS
556.5; the predicted means of the they were on a fresh pasture i.e. on first days of
df53
percentages of time spent lying at pasture were 25.9 experimental periods, and between 68.2 and 73.4
and 26.5 on ‘far’ pastures and 32.6 and 31.1 on of these 15 h when they were on these pastures for
‘near’ pastures S.E.51.6; VWS 527.0; and the
the last time i.e. on fourth days of experimental
df53
predicted means of the percentages of time spent on periods predicted means. The cows appeared to
the central alley between the pasture and the barn spend a significantly bigger part of the time that they
were 7.3 and 5.5 on ‘far’ pastures and 1.6 and 2.5 on could be outdoors at pasture at higher sward heights
‘near’ pastures S.E.51.2; VWS 5125.1. The
S.E.D.51.0; VWS 5122.5; P,0.01. The same
df53 df53
‘far’ pastures differed significantly from the ‘near’ significant effect of sward height was found for the
pastures in all these cases P ,0.01. The predicted time spent grazing: the cows spent between 93.5 and
mean of the percentage of time spent grazing was 95.5 of the time that they were eating forage
45.5 when the cows were on a ‘far’ pasture for the between 5:30 and 20:30 h grazing when they were
first time and 38.8 when they were on a ‘far’ pasture on a fresh pasture, and between 86.7 and 87.7 of
for the second time S.E.51.1; VWS 541.0; P,
this time when they were on these pastures for the
df53
0.01. These figures for the time spent at the feeding last time predicted means S.E.D.51.0; VWS
5
df53
Table 3
c
Predicted means of the cows’ time budget in the strip grazing experiment based on on-line computer registrations 435 24-h periods Time spent min per
Period 1 Period 2
Period 3 period 4
S.E.D. VWS
df53
cow per day: 146 m
360 m 355 m
168 m In lying area
519.2 532.7
559.7 541.5
14.3 8.3
b a
b b
In feeding area 154.5
126.7 140.7
150.7 7.0
21.0
a a
a b
In AMS area 37.4
38.0 40.8
47.9 2.4
20.7
b a
b b
Indoors 729.2
700.5 738.5
738.0 11.3
15.6
a b
a a
Outdoors 709.2
741.3 699.5
700.7 11.4
16.8
a,b
Different superscripts in a row indicate a significant difference between experimental periods P ,0.01.
c
The distance between the pasture and the barn was different in different experimental periods; standard error of difference S.E.D. is mentioned as indication of deviation.
C .C. Ketelaar-de Lauwere et al. Livestock Production Science 65 2000 131 –142
139
70.5; P ,0.01. The cows spent between 71.3 and indoors by the cows between 10:00 and 17:00 h
90.8 of the time that they were lying between temperature effect50.4247; S.E.50.1; P ,0.01.
05:30 and 20:30 h at pasture predicted means. This The average black globe temperature between 10:00
was not related to sward height. and 17:00 h on these days ranged from 18.9 to
In the strip grazing experiment distance, the 32.18C. No such effects were found on the other days
cows spent between 79.5 and 86.0 of the time that of the rotational grazing experiment and in the strip
they could be outdoors at pasture, between 85.9 and grazing experiment.
91.2 of the time that they were eating forage On one of the observation days of the rotational
between 05:30 and 20:30 h grazing and between 91.1 grazing experiment lying time was much shorter than
and 96.3 of the time that they were lying between on all other observation days including those of the
05:30 and 20:30 h at pasture predicted means. strip grazing experiment. This day was the rainiest
Although some significance were found between of all observation days: it rained for 61.1 of the
these figures, they could not be related to the time that the cows could be outdoors.
distance between the pasture and the barn. 3.3.2. Time intervals between cows entering the
4. Discussion
