and 0.7 kg. Milk yield was not significantly different after a 60-min interval, possibly because the effect of a delay of milking after stimulation disappeared during the 60-min
interval while milk production resumed. The effect of delay of milking on cow behaviour was not investigated.
Our aim was to estimate the well-being of unmilked cows by comparison with milked cows and to relate these findings to the situation of automatic milking. Our hypothesis
Ž .
was that omitted milking cluster attachment failure unsettles a cow in some way and this will be reflected by her behaviour.
2. Materials and methods
In this trial we studied the behaviour of cows after their return from the milking Ž
parlour where some had been milked and others not. For ethical reasons not subjecting .
the cows to unreasonable levels of discomfort it was considered that an observation period of 1 h was enough to reveal any effect of omitted milking; moreover, the cows in
the trial were in the second half of lactation. The unmilked cows were milked immediately after the observation period had ended.
2.1. Animals, housing, procedures We aimed to take into account all behavioural traits that could be influenced by
omitted milking. The milking order during all visits to the milking parlour was registered, as were any aggressive interactions between cows and where these occurred.
The milk production during the trial was also monitored. The trial was carried out with 12 Holstein–Friesian cows, divided equally between
Ž .
first and second lactations. On average, the cows were 209 SD s 42 days in their lactation. Mean milk yield at the beginning of the trial was 21.4 kgrday for cows in
their first lactation and 27.9 kgrday for cows in their second lactation. Ten cows were in calf and two barren.
Ž .
The cows were kept in a compartment of a loose housing system Fig. 1 with a slatted floor, a lying area with the same number of cubicles as the number of cows, and
Ž .
a separate feeding area with six automatic feeders Devir et al., 1996 . One watering trough and one salt block were placed in the feeding area. Cows were fed a complete
Ž .
diet mixture of grass silage, corn silage and concentrate with 43.5 of dry matter ad libitum in an automatic forage installation. The cows were given 0.5 kg concentrate per
milking. The compartment for the experimental cows was located near the milking parlour
Ž .
Fig. 1 . During a habituation period of 12 days the cows were milked 2 times per day Ž
. at 05.45 h and 15.45 h and learned to follow routine that was applied in the trial
thereafter. Prior to the milkings they were brought as a group to the waiting area in front of the milking parlour. Milking took place in a double-three open-tandem parlour. The
cows could enter this parlour through two automatically controlled double gates. The first six cows milked had to wait for the other six cows in the return alley near the
compartment. When all cows had been milked, they were allowed to enter the
Fig. 1. Layout of compartment of the cubicle house used in the trial.
compartment. In the habituation period the cows were subjected to an identical proce- dure of udder preparation executed by a milker. This procedure consisted of four circular
cleaning movements on the surface of the udder and three squeezes per teat. After the habituation period the 16-day trial with omitted milkings started. The
omitted milkings were applied only during the afternoon milkings. Each day, 3 of the 12 Ž
. cows
never the same 3 as the previous day, and always a different trio were
deliberately omitted from milking. If the preparation of the udder was not followed by milking, these cows were released from the milking stalls 2 min later. This mimicked
the robot milking situation where the attachment attempt is aborted after 2 min Ž
. Stefanowska et al., 1999a . During the 16 days, each cow was subjected to four omitted
milkings. The omitted milkings for the same cow were at least 2 days apart. Immediately after an observation period of 1 h, all cows were simultaneously herded
into the waiting area in front of the milking parlour for the three unmilked cows to be milked. The nine previously milked cows walked through the milking parlour, but the
three unmilked cows were milked after another preparation of the udder.
2.2. Collection of data All cows were videoed in their compartment for the first hour after their return from
the milking parlour. The duration of the following activities, rounded off to the nearest
minute, was taken from the video registration: eating, standing in feeding area or lying area, standing in cubicles and lying. Furthermore, the time until the occurrence of eating,
drinking, lying, urination and defecation was taken from video rounded off to the nearest Ž
. minute. The occurrence of aggressive acts including physical contact was recorded,
Ž noting the cows involved and the output of aggressive interaction e.g., aggressor and
. recipient .
Ž .
Individual intake duration, amount of a complete diet as well as milk yield were registered automatically.
Ž After omitted milking all cows were observed visually for leakage of milk qualita-
. tive: yes or no .
Milking order of cows was observed during morning and afternoon milking as well as during the third visit to the milking parlour. The milking order was defined on the basis
of whether the cow came to the milking parlour within the first batch of six cows. In this Ž
way, after the 16 days of the trial, each cow had received three numbers each in the .
possible range 0–16 equal to the numbers of visits in which she came within the first batch of six cows during the morning, the afternoon and also during the third herding
into the milking parlour. Additionally the order of entering of the compartment after Ž
afternoon milking defined in the same way as for the milking parlour, e.g., being one of .
the first six cows was observed. One important aspect of this experiment was that after each milking the first batch of
six cows had to wait in the return alley for about 10 min until they were joined by the Ž
. remaining six cows arriving from the milking parlour see Fig. 1 . The waiting cows
may have urinated andror defecated. It was also possible that waiting in the return alley affected the behaviour during the observational period. To avoid complications, the
observations started after all cows had entered the compartment, rather than as soon as the first six cows entered the compartment. This enabled us to observe each cow while
within the entire group: this is especially important in the context of aggressive interactions.
2.3. Data analyses Ž
The Genstat 5 statistical package was used for the analyses Genstat 5 Committee, .
1998 . Ž .
1 The time budgets for five different activities were analysed by a generalised linear Ž
. model GLM . The probabilities of the occurrence of the activities mentioned above
were transformed to log-probabilities h where j is the index for the category. The effect
j
of a treatment on these probabilities was assumed to be linear on the log-scale: h s h q b
1
Ž .
ji j
ji
Ž .
where b represents the effect of the factor level i
i s omitted milking on the
ji
Ž log-probability for category j see McCullagh and Nelder, 1989 for more detailed
. information on models for the analysis of categorical data .
Ž . Ž
. 2 Occurrence of different events yesrno during the 1-h observational period was
Ž .
analysed by a generalised linear mixed model GLMM using a logistic link function: log mr 1 y m
s b x q uz 2
Ž .
Ž .
Ž .
where m is a binary variable representing whether or not an event has occurred, b Ž
represents fixed effects and u represents the random effects for cows McCullagh and .
Nelder, 1989; Engel and Keen, 1994 for the analysis of binary data . Ž .
3 The time until the occurrence of different events was analysed according to a Ž
. linear mixed model LMM , where the variance was assumed to be constant and
Ž .
normally distributed Engel, 1990 : m s b x q uz
3
Ž .
where m represents the expected value of the time that has elapsed until the occurrence Ž .
of a certain event and b and u are the same as in Eq. 2 . Analysis of time until occurrence is complicated by the fact that observations ended after 60 min. This was
corrected by the method described by Taylor for so-called censored observations Ž
. Taylor, 1973 .
Ž . 4 The number of aggressive interactions induced by a certain cow within the 1-h
Ž .
observational period was analysed by a generalised linear mixed model GLMM with a logarithmic link function:
log m s b x q uz 4
Ž .
Ž .
where m is the number of aggressive interactions and b is a variable representing the effect of omitted milking or milking on the aggression of a cow. It was assumed that
Ž variance increases proportionally to the expected response value see McCullagh and
. Nelder, 1989 for loglinear models on counted data .
Ž . 5 Data from the automatic forage installation and data about milk production were
Ž . Ž
. analysed with a linear mixed model LMM
see Eq. 3 . Ž .
6 The number of changes between automatic forage feeders was analysed with a Ž
. Ž .
generalised linear mixed model GLMM see Eq. 4 .
Ž .
The analyses 1–6 included the effect of rank in the milking order, as well as the Ž
. effect of lactation number and interaction between these factors if any .
The milking order of cows during three visits to the milking parlour and also the order during return to the compartment after the second visit to the milking parlour were
Ž .
compared using a Spearman correlation coefficient Siegel and Castellan, 1988 . The place where aggressive interactions between cows occurred after milking and after
2
Ž .
omitted milking was compared by a x test Siegel and Castellan, 1988 .
3. Results
