The effect of omitted milking on the behaviour of cows in the context of cluster attachment failure during automatic milking

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1 Ž. Applied Animal Behaviour Science The effect of omitted milking on the ehaviour of cows in the context of cluster attachment failure during automatic milking J. Stefanowska a,), M. Plavsic, A.H. Ipema a, M.M.W.B. Hendriks a a Institute of Agricultural and EnÕironmental Engineering IMAG-DLO, Mansholtlaan 10-12, P.O. Box 43, 6700 AA Wageningen, Netherlands LiÕestock Research Institute, NoÕi Sad, YugoslaÕia Accepted 7 Decemer 1999 Astract In rootic milking there is always a slight chance of failure to attach the milking cluster. Attachment failure is most likely for cows whose udder conformation is less convenient for root attachment. In general, after milking failure cows try to revisit the milking root if they are not sent to a separate area. Since it is difficult to estimate the effect of milking failure on such a cow and her welfare in conditions of rootic milking, a specific 16-day trial was conducted on 12 cows. These cows were milked in a milking parlour with six milking stalls. Each afternoon milking, three cows were not milked. All the cows were closely oserved in the cuicle house for 1 h after the afternoon milking. Thereafter, all cows were rought to the milking parlour the third time and the three unmilked cows were milked. In total, each cow was oserved 12 times after milking and four times after omitted milking. The following ehavioural traits were registered: time udget for the 1 h, occurrence and time until eating, drinking, lying, urination and defecation, and aggressive interactions. Milking order was defined on the asis of how often a cow came to the milking parlour in the first atch of six cows. Moreover, the data related to the milk yield and the use of the automatic feeding installation with the complete diet were analysed. After omitted milking, only the cows from the first atch stood longer in cuicles Ž 14.2 min of 1 h. and lay less Ž 5.4 min of 1 h. than milked cows of the same atch Žrespectively 7.0 min and 16.3 min for standing and lying in cuicles.ž P After omitted milking, cows urinated earlier and more frequently Ž 64.5%. than milked cows Ž 36.3%. Ž P Ž oth atches.. There were no ) Corresponding author. Tel.: q ; fax: q Ž. address: j.stefanowska@imag.dlo.nl J. Stefanowska r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž. PII: S

2 278 J. Stefanowska et al.rapplied Animal BehaÕiour Science statistically significant differences in eating time and feed intake after milking and omitted milking. Milk yield per cow averaged 24.9 kg during days with omitted Ž delayed y 1 h. milking and 25.3 kg during the days without omitted milking Ž P It was concluded that cows show some signs of discomfort after omitted milking Ž urination.; this discomfort seemed to e greater in cows coming earlier to the milking parlour Ž afterwards they preferred to stand rather than to lie.. The 60% of cases of milk leakage found after omitted milking indicates that failed cluster attachment can e accompanied y an extra risk factor for the occurrence of mastitis. However, omitted milking as a treatment did not influence feeding and aggressive ehaviour or milking order when unmilked cows were rought to the milking parlour the third time together with the milked cows. Our methods and results can e useful for estimating the effects of root milking failures on a cow. Future studies should pay particular attention to high-yielding cows and to longer periods of delayed milking. q 2000 Elsevier Science B.V. All rights reserved. Keywords: Omitted milking; Cluster attachment failure; Milk leakage; Automatic milking; Dairy cattle; Behaviour 1. Introduction Milking cluster attachment failures during automatic milking occur in the range from a few percent of cases to 12% Ž Ipema et al., and 15% Ž Mottram et al., On commercial farms, after milking failure a cow is mostly diverted to a separate area and waits for a stockman, who takes her ack to the root and supervises root attachment. In experimental studies with an automatic milking system Ž AMS. where cow ehaviour was studied, cows were not separated after milking failure. The stockman intervened twice a day to ensure that any cows with failed milking andror too long an interval since the previous milking were milked Ž Stefanowska et al., 1999a,.. These cows were rought to the milking root individually. Usually, the same cows, ones whose udder conformation is less convenient for root attachment, failed to e milked. It was oserved that when a visit to the AMS ended with a milking failure, cows returned to the AMS of their own free will after an average of 2 h, whereas milked cows returned after an average of 5 h Ž Stefanowska et al., 1999a,.. It seems likely that a cow returns after a milking failure ecause she wants to eat concentrate Ždispensing stops after milking failure., or she expects to e milked, or oth. It is not known whether cluster attachment failure has implications for the well-eing and milk yield of a cow. It is difficult to study the effects of milking failure in conditions of voluntary visits to the root, since the conditions of individual cases are uncontrollale Ždifferent milking intervals; different situation related to rest and feeding.. In these circumstances it is difficult to explain individual reaction to milking failure and to compare individual cases with each other. However, a trial on the effects of omitted milking in a traditional milking parlour might simulate the possile effects of cluster attachment failure. It proceeds under human supervision and can e controlled adequately. This paper descries such a trial. Previous studies Ž Mayer et al., 1984; Pfeilsticker et al., on the effect of the time interval etween pre-milking stimulus and actual milking on milk yield found that intervals of 3 and 15 min caused milk yield to decrease significantly y respectively 0.3

3 J. Stefanowska et al.rapplied Animal BehaÕiour Science and 0.7 kg. Milk yield was not significantly different after a 60-min interval, possily ecause 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 ehaviour was not investigated. Our aim was to estimate the well-eing of unmilked cows y comparison with milked cows and to relate these findings to the situation of automatic milking. Our hypothesis was that omitted milking Ž cluster attachment failure. unsettles a cow in some way and this will e reflected y her ehaviour. 2. Materials and methods In this trial we studied the ehaviour of cows after their return from the milking parlour where some had een milked and others not. For ethical reasons Žnot sujecting the cows to unreasonale levels of discomfort. it was considered that an oservation 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 oservation period had ended Animals, housing, procedures We aimed to take into account all ehavioural traits that could e influenced y omitted milking. The milking order during all visits to the milking parlour was registered, as were any aggressive interactions etween 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 etween first and second lactations. On average, the cows were 209 Ž SDs42. days in their lactation. Mean milk yield at the eginning 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 arren. The cows were kept in a compartment of a loose housing system Ž Fig. 1. with a slatted floor, a lying area with the same numer of cuicles as the numer of cows, and a separate feeding area with six automatic feeders Ž Devir et al., One watering trough and one salt lock were placed in the feeding area. Cows were fed a complete diet Ž mixture of grass silage, corn silage and concentrate. with 43.5% of dry matter ad liitum 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 haituation period of 12 days the cows were milked 2 times per day Ž at h and h. and learned to follow routine that was applied in the trial thereafter. Prior to the milkings they were rought as a group to the waiting area in front of the milking parlour. Milking took place in a doule-three open-tandem parlour. The cows could enter this parlour through two automatically controlled doule 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 een milked, they were allowed to enter the

4 280 J. Stefanowska et al.rapplied Animal BehaÕiour Science Fig. 1. Layout of compartment of the cuicle house used in the trial. compartment. In the haituation period the cows were sujected to an identical procedure of udder preparation executed y a milker. This procedure consisted of four circular cleaning movements on the surface of the udder and three squeezes per teat. After the haituation 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 cows Ž never the same 3 as the previous day, and always a different trio. were delierately omitted from milking. If the preparation of the udder was not followed y milking, these cows were released from the milking stalls 2 min later. This mimicked the root milking situation where the attachment attempt is aorted after 2 min Ž Stefanowska et al., 1999a.. During the 16 days, each cow was sujected to four omitted milkings. The omitted milkings for the same cow were at least 2 days apart. Immediately after an oservation 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 e milked. The nine previously milked cows walked through the milking parlour, ut the three unmilked cows were milked after another preparation of the udder 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

5 J. Stefanowska et al.rapplied Animal BehaÕiour Science minute, was taken from the video registration: eating, standing in feeding area or lying area, standing in cuicles and lying. Furthermore, the time until the occurrence of eating, drinking, lying, urination and defecation was taken from video rounded off to the nearest minute. The occurrence of aggressive acts Ž including physical contact. was recorded, noting the cows involved and the output of aggressive interaction Že.g., aggressor and recipient.. Individual intake Ž duration, amount. of a complete diet as well as milk yield were registered automatically. After omitted milking all cows were oserved visually for leakage of milk Žqualita- tive: yes or no.. Milking order of cows was oserved during morning and afternoon milking as well as during the third visit to the milking parlour. The milking order was defined on the asis of whether the cow came to the milking parlour within the first atch of six cows. In this way, after the 16 days of the trial, each cow had received three numers Žeach in the possile range equal to the numers of visits in which she came within the first atch 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 afternoon milking Ždefined in the same way as for the milking parlour, e.g., eing one of the first six cows. was oserved. One important aspect of this experiment was that after each milking the first atch of six cows had to wait in the return alley for aout 10 min until they were joined y the remaining six cows arriving from the milking parlour Ž see Fig. 1.. The waiting cows may have urinated andror defecated. It was also possile that waiting in the return alley affected the ehaviour during the oservational period. To avoid complications, the oservations started after all cows had entered the compartment, rather than as soon as the first six cows entered the compartment. This enaled us to oserve each cow while within the entire group: this is especially important in the context of aggressive interactions Data analyses The Genstat 5 statistical package was used for the analyses ŽGenstat 5 Committee, Ž. 1 The time udgets for five different activities were analysed y a generalised linear model Ž GLM.. The proailities of the occurrence of the activities mentioned aove were transformed to log-proailities hj where j is the index for the category. The effect of a treatment on these proailities was assumed to e linear on the log-scale: hjishjqji Ž 1. where represents the effect of the factor level i Ž is omitted milking. ji on the log-proaility for category j Žsee McCullagh and Nelder, 1989 for more detailed information on models for the analysis of categorical data.. Ž. 2 Occurrence of different events Ž yesrno. during the 1-h oservational period was analysed y a generalised linear mixed model Ž GLMM. using a logistic link function: log mrž 1ym. s xquz Ž 2. Ž.

6 282 J. Stefanowska et al.rapplied Animal BehaÕiour Science where m is a inary variale representing whether or not an event has occurred, represents fixed effects and u represents the random effects for cows ŽMcCullagh and Nelder, 1989; Engel and Keen, 1994 for the analysis of inary data.. Ž. 3 The time until the occurrence of different events was analysed according to a linear mixed model Ž LMM., where the variance was assumed to e constant and normally distriuted Ž Engel, 1990.: ms xquz Ž 3. where m represents the expected value of the time that has elapsed until the occurrence of a certain event and and u are the same as in Eq. Ž. 2. Analysis of time until occurrence is complicated y the fact that oservations ended after 60 min. This was corrected y the method descried y Taylor for so-called censored oservations Ž Taylor, Ž. 4 The numer of aggressive interactions induced y a certain cow within the 1-h oservational period was analysed y a generalised linear mixed model Ž GLMM. with a logarithmic link function: logž m. s xquz Ž 4. where m is the numer of aggressive interactions and is a variale representing the effect of omitted milking or milking on the aggression of a cow. It was assumed that variance increases proportionally to the expected response value Žsee McCullagh and Nelder, 1989 for loglinear models on counted data.. Ž. 5 Data from the automatic forage installation and data aout milk production were analysed with a linear mixed model Ž LMM. Ž see Eq. 3.. Ž. 6 The numer of changes etween automatic forage feeders was analysed with a generalised linear mixed model Ž GLMM. Ž see Eq. 4.. The analyses Ž 1 6. included the effect of rank in the milking order, as well as the effect of lactation numer and interaction etween these factors Ž 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 compared using a Spearman correlation coefficient Ž Siegel and Castellan, The place where aggressive interactions etween cows occurred after milking and after 2 omitted milking was compared y a x test Ž Siegel and Castellan, Results The oservations on the ehaviour of milked and unmilked cows started immediately after the entire group had entered the compartment after returning from the milking parlour. The entrance led to the lying area Ž see Fig. 1., from where at least half of the cows went immediately to the feeding area. In the course of 1 h, the percentage of cases of eating or standing in the feeding area remained the same, whereas the percentage of cases of lying increased gradually, though this tendency was less marked in the unmilked cows Ž Fig. 2.. The percentage of cases of standing in the cuicles was almost

7 J. Stefanowska et al.rapplied Animal BehaÕiour Science Fig 2. Activities of cows during the 1-h oservational period after milking or omitted milking. always higher for the unmilked than for the milked cows. The impression from Fig. 2 is confirmed y the analysis of time udget per hour Ž see Tale 1.. The difference was significantly attriuted to the cows that were in the first atch that came to the milking parlour. After omitted milking, these cows stood longer in the cuicles Ž 14.2 min of 1 h. and lay less Ž 5.4 min of 1 h. than milked cows for whom the corresponding figures were 7.0 min for standing and 16.4 min for lying in cuicles.ž P There was no significant difference etween milked and unmilked cows in time spent on eating and standing in the eating or in the lying area Ž taken from video.. The proailities of the occurrence of eating, drinking and lying as well as defecation and urination and the predicted time intervals for the occurrence of these activities in milked and unmilked cows are given in Tale 2. Proaility of cows eating forage was 80% Ž SEM s 4%. after milking and 85% Ž SEM s 7%. after omitted milking Ždifference not significant.. Proaility of cows drinking was 73% Ž SEMs 4%. after milking and 71% Ž SEMs 7%. after omitted milking Ž difference not significant.. On average, the cows ate and drank efore lying. Unmilked cows were more likely to urinate than

8 284 J. Stefanowska et al.rapplied Animal BehaÕiour Science Tale 1 Predicted time udget Ž min. of 12 cows during 1 hour following their visit to the milking parlour. In 16 trials, each cow had not een milked Ž 4=. or milked Ž 12=.; standard error of means in parenthesis Order of coming to the milking parlour Activity Milked cows Unmilked cows First atch of six cows eating forage 13.9 Ž Ž 3.5. standing in eating area 17.2 Ž Ž 3.1. standing in lying area 5.5 Ž Ž 1.9. standing in cuicle Ž. a a 14.2 Ž 3.0. lying 16.4 Ž 1.7. a 5.4 Ž 1.8. Second atch of six cows eating forage 12.7 Ž Ž 2.8. standing in eating area 13.7 Ž Ž 2.8. standing in lying area 5.6 Ž Ž 1.8. standing in cuicle 10.3 Ž Ž 2.2. lying 17.7 Ž Ž 2.9. a Ž. Different letters in one row indicate statistically significant difference P milked cows Ž respective proailities 64% and 36%, P and the time interval until urination was predicted to e shorter for unmilked cows Ž56 min versus 70 min for milked cows, P Neither the proaility of defecation nor the time interval to occurrence of defecation was significantly influenced y omitted milking. The milking order was not reflected in the order in which the cows entered the compartment prior to the start of the oservations Ž r sy0.43, not significant. s, ecause the cows moved around in the return alley. However, milking order was reflected in the use of the automatic forage installation. Cows that were in the first atch to enter the milking parlour spent more time eating, changed feeding places more and ate more feed. Intake of feed was also influenced y lactation: during the 1-h oservation period, cows in the second lactation ate 4.8 kg of forage on average, whereas cows in the first lactation ate 3.6 kg Ž P The omitted milking did not significantly influence time Tale 2 Proaility of occurrence of different activities for the 12 cows during 1 h after returning from the milking parlour, where three cows had een sujected to omitted milking, and predicted time until their occurrence for milked and unmilked cows; standard error of mean in parenthesis Activity Milked cows Unmilked cows Proaility of activity eating forage 0.80 Ž Ž drinking 0.73 Ž Ž lying down 0.59 Ž Ž defecation 0.48 Ž Ž urination Ž. a a 0.64 Ž Time until occurrence of activity Ž min. eating forage 33.1 Ž Ž 2.4. drinking 34.5 Ž Ž 2.4. lying down 52.0 Ž Ž 2.4. defecation 61.9 Ž Ž 2.7. urination 70.2 Ž 4.0. a 55.8 Ž 2.3. a Ž. Different letters in one row indicate a statistically significant difference P

9 J. Stefanowska et al.rapplied Animal BehaÕiour Science spent in the forage installation, the forage intake or the rate of eating forage, as analysed on the asis of data from automatic forage installation. One hour after an omitted milking, cows gave on average kg milk; this was more than what normally milked cows gave Ž kg, P Ž Tale 3.. The following morning the opposite was true: cows sujected to omitted milking the previous afternoon gave kg milk on average, whereas cows normally milked gave kg Ž P Daily milk yield Žcalculated as afternoon plus next morning milk yields. on days with omitted milking averaged kg in comparison with kg on days without omitted milking Ž P Cows that were most frequently in the first atch during afternoon milking had a higher daily milk yield and a higher morning milk yield. This relation was not found for the afternoon milk yield, ecause of the direct effect of omitted milking. Throughout the experiment, the same milking order was oserved, as indicated y the correlation coefficient: r sq0.69 etween morning and afternoon milking Ž P s ; r sq0.78 etween afternoon milking and the third visit Ž 1 h later. s of all cows to the milking parlour Ž for the three unmilked cows to e milked. Ž P Tale 3 Predicted milk yield of experimental cows Ž kgrcow. and factors found to have significant influence on it; standard error of mean in parenthesis Milk production in the afternoon cows normally milked cows milked 1 h later Ž. a a Ž lactation numer first second 9.57 Ž a Ž Milk production the next morning cows normally milked cows milked 1 h later Ž a Ž lactation numer first second Ž a Ž milking order first atch second atch Ž a Ž Daily milk production days without omitted milkings days with omitted milking Ž c Ž d lactation numer first second Ž a Ž milking order first atch second atch Ž a Ž a Different letters in one row indicate a statistically significant difference Ža, at P level; c,d at P level..

10 286 J. Stefanowska et al.rapplied Animal BehaÕiour Science The average numer of aggressive interactions was 2.2 per cowrh after milking and 2.6 per cowrh after omitted milking Ž difference not statistically significant.. The numer of aggressive interactions was not related to the milking order or to the lactation numer. The proportion of numers of eing the aggressor to the sum of eing the aggressor and of eing the recipient of the aggression was similar after milking and after omitted milking Ž r sq0.86, P s. Analysis of where the 468 aggressive interac- tions Ž 337 of milked cows and 131 of cows after omitted milking. took place revealed that cows were most aggressive at the forage feeders Ž 43.4% of cases. and the water trough Ž 28.0% of cases.. Aggressive interactions also took place, ut less, in the feeding area Ž 13.5% of cases., around the salt lock Ž 7.0% of cases. and in the lying area Ž6.6% of cases.. Pushing a cow away from her lying place happened exceptionally Žseven. 2 cases, 1.5% of all. The x test revealed no difference in the distriution of the location of the aggressive acts of milked and unmilked cows. Milk leakage from the udder was oserved in 60% of cases after omitted milking. In 5 out of 12 cows milk leakage was always oserved after omitted milking Že.g., for four occasions of omitted milking., in three cows it was never oserved Že.g., during any of four occasions.; milk leakage was oserved irregularly in the remaining four cows after omitted milking. No relation was found etween milk leakage after omitted milking and ehaviour after omitted milking or milk yield. 4. Discussion 4.1. Experiences of cows induced y omitted milking It was assumed that cows perceive a mismatch etween the familiar daily routine Ž coming to milking parlour, preparation of the udder, milking. and the outcome of the visit Ž no milking.. There would have een physical sensations too: during preparation for milking the oxytocine reflex stimulates inflow of milk into the cistern of the udder, and therefore if no milking follows, the udder is likely to ecome distended. Incidences of leakage of milk oserved after omitted milking were also registered in previous research in some cows that were rought in groups to the milking root ut had to wait their turn Ž Stefanowska et al., as well as in cows waiting for access to a traditional milking parlour. The leakage is a consequence of milk accumulating in the cistern of the udder and is reinforced y preparation for milking not followed y milking. Cows differ in the occurrence of milk leakage, depending on differences in milk yield, individual reactivity and, last ut not least, the difference in the functioning of the small sphincter muscles closing the milk canals of teats. It was assumed that omitted milking was experienced y cows externally as an unexpected situation and internally as pressure or at least as the lack of the familiar feeling of a milked-off udder. It is striking that during the oservations the cows whose milking had een omitted urinated twice as often and earlier than milked cows. This difference was highly significant, even though the cows certainly also eliminated in the return alley, where their ehaviour was not oserved. This is similar to the finding of a study on cows who

11 J. Stefanowska et al.rapplied Animal BehaÕiour Science were not selected for milking until they were in the milking stall with a root: cows after milking failure or a no-milking visit urinated more often in the exit area from milking stalls than milked cows Ž Stefanowska et al., 1999a.. Furthermore, in three trials on the ehaviour of cows sujected to walk-through selection on their way to a milking root, it was oserved that cows refused access to the root urinated in the passage with walk-through selection more frequently than cows for whom the gate to the milking stalls with root had opened Ž Stefanowska et al., The urination was presumaly the cows response to the uncertainty aout their situation. Hopster Ž reported the occurrence of elimination y cows exposed to a new environment, ut did not distinguish etween urination and defecation. Marchal et al. Ž oserved a decrease in elimination y cows after haituation to an automatic milking system. The empirical oservations of farmers are that elimination increases after the installation of a new milking parlour. Kilgour and Alright Ž suggested that stress stimulated cows to defecate and urinate. It is not known why in the present trial as well as in earlier trials reported y Stefanowska et al. Ž 1999a,. the given situation Ž with stress factor. had more impact on urination than on defecation. Another noteworthy result was that cows that came to the milking parlour in the first atch and were sujected to omitted milking stood significantly longer in the cuicles and lay significantly shorter than milked cows during the following period of 1 h. It seems proale that ecause they were more motivated for milking they experienced more disruption. Moreover, ecause they had a somewhat higher milk yield Ž26.0 kg of milkrday in comparison to 23.2 kg of milkrday for cows that were more frequently in the second atch. they experienced more discomfort than cows from the second atch. Ipema et al. Ž reported that high yielding cows stood longer in cuicles than low yielding cows and that after introduction of more frequent milking they egan to lie longer in the cuicles. The cows that were present most frequently in the first atch were four cows in second lactation and two cows in first lactation. They were also in the first atch during the third visit to the milking parlour for milking the three unmilked cows. This suggests that a cow s motivation to lead the way to the milking parlour may e related to milk yield, age, ut maye also to individual attriute Does omitted milking stress the cow? The question arises whether we can qualify the experience of omitted milking as stress. Hopster Ž defined stress as a state when the expectations or ojectives of an animal do not match the oserved and sensed environment Ž external or internal.. Unspecific reactions to stressors take place when influencing factors may exert effect on psychological status Ž uncertainty, fear. Ž Hopster, In this context we may hypothesise that urination after omitted milking is an unspecific reaction to the disturance of daily routine Ž e.g., omitted milking.. During stress, the concentration of adrenalin and noradrenalin in the lood and also locally released noradrenalin inhiit milk removal Ž Hamann, Algers Ž is convinced that stress can affect milk production, ut it is difficult to state whether such effects are direct or indirect. In our trial, cows after omitted milking gave 0.7 kg milk more during the milking 1 h later than cows normally milked Ž P This difference can e attriuted to the additional Ž third. preparation

12 288 J. Stefanowska et al.rapplied Animal BehaÕiour Science of the udder and to the extra hour elapsed efore milking. During the next morning cows after omitted milking gave 1.1 kg milk less than cows normally milked Ž P This can e attriuted to the 1 h shorter milking interval. However, the difference of 0.4 kg milk less Ž P on days with omitted milking than on days without omitted milking might e caused y the milk ejection process eing interrupted during days with omitted milking; this agrees with the findings of Bruckmaier and Blum Ž on oxytocine release and milk removal in ruminants. It is clear that omitted milking did not influence either the time spent in the forage installation or the amount of forage eaten. All cows ate intensively during the 1 h after returning from the milking parlour. During that hour they ate on average 1.9 kg of dry matter from the mixed ration. Compare this with a daily intake of circa 20 kg of dry matter from forage and concentrate as registered in the same installation during another trial Ž Metz-Stefanowska et al., The rate of eating of the mixed ration was circa 100 g dmrmin. This is higher than the mean daily forage eating rate of 83 g dmrmin as reported y Metz-Stefanowska et al. Ž 1993., proaly ecause eating intensity depends on kind of forage and way of rationing and it varies throughout the day. Metz- Stefanowska et al. Ž 1992, descried that after milking in a traditional milking parlour and also after rootic milking, cows were at the feeding rack Žoptionally automatic feeding installation. much more frequently than during any other time. Tyler et al. Ž oserved that when forage was availale, cows stayed in the feeding area after milking longer than when no forage was availale. It is interesting that the numer of aggressive acts and the individual proportion of eing aggressorrrecipient was not influenced y omitted milking either. The average numer of 30 aggressive acts within the group during the 1 h of oservations agrees with oservations of Metz Ž on aggressive interactions etween 14 cows provided with a feeding rack with 7 places and fed ad liitum. According to Metz, the descried situation was not as competitive as it can e in case of not feeding ad liitum. Omitted milking was not a situation that changed aggression eyond an estalished level in a group Relating the results of research on omitted milking to rootic milking failures In other research conducted in circumstances of automatic milking, cows returned to the AMS after milking failure earlier than milked cows Ž Stefanowska et al., 1999a,.. Compared with the other cows they returned to the AMS without lying or eating more often Ž Ketelaar-de Lauwere et al., The cows with recurrent milking failure ecause their udder conformation was less suitale for root attachment could develop their own strategy to try to resolve their situation y returning, with whatever motivation Ž to eat concentrate andror to e milked.. This was not the case in our trial: during the third visit to the milking parlour the unmilked cows did not reak with the estalished milking order. It is widely accepted that cows that undergo daily routine as a group react to stress more passively Ž Hopster, After failure of cluster attachment, the cows in our earlier trials Ž Stefanowska et al., 1999a,. undertook action: they came ack. However, the experiences of these cows after milking failure of a root should not e underestimated. After repeated failures they wandered around, which negatively influ-

13 J. Stefanowska et al.rapplied Animal BehaÕiour Science enced their time udget Ž idle time at the expense of eating or lying.. Efficient use of time udget is very important for high yielding cows ecause they must eat and lie a lot. These cows urinated in the exit area of the AMS more often than milked cows Ž Stefanowska et al., 1999a.. In the case of a cowshed with a root and animals given access to the pasture dependent on milking status, cows may e denied access to outdoors after milking failure of the root. They may pay many unsuccessful visits to the root efore finally eing allowed outdoors, mostly after the farmer has intervened. It is essential to estalish some time limits for human intervention in the case of milking failure, especially for high yielding cows and when successful milking is a prerequisite for eing allowed to leave the arn or during the periods of longer asence of the farmer Že.g., at night.. It would e possile to estimate the well-eing of cows after the failure of the root attachment on the asis of their activities following the failure y looking at their idle time and occurrence of urination. The leakage of milk oserved after omitted milking as well as after cluster attachment failure during rootic milking forms a risk for the udder health of cows. Elers et al. Ž reported that leakage of milk from the udder is one of the factors associated with clinical mastitis at herd level. 5. Conclusions Ž. 1 After omitted milking, all cows showed some signs of discomfort Ž urination.; those that visited the milking parlour most frequently in the first atch Žmore milk and higher motivation. showed some signs of discomfort y standing in the cuicles afterwards instead of lying. Ž. 2 The leakage of milk that can occur after omitted milking or after cluster attachment failure during rootic milking is a risk factor for mastitis. Ž. 3 The treatment was not so influential that it caused cows whose milking had een omitted to change the way they visited the milking parlour when they were finally rought for milking together with already milked cows. This is supported y other findings that during 1 h after omitted milking cows did not eat more Ž or less. and were not more Ž or less. aggressive than milked cows. A similar tendency was oserved for drinking. Ž. 4 It seems proale that this approach will e useful for estimating possile direct effects of a root milking failure on a cow. Future studies should examine the consequences of a root milking failure in high yielding cows and for a period longer than 1 hour. Acknowledgements The authors wish to thank Dr. R. Braam for his useful comments on earlier drafts as well as Dr. P. Koene en Prof. Dr. P.R. Wiepkema for their perceptive comments on ethological aspects of this paper.

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15 J. Stefanowska et al.rapplied Animal BehaÕiour Science Stefanowska, J.,Sonck, B.,Keen, A., Behaviour of cows milked in fixed milking periods with automatic milking system on practical farms Ž in Dutch.. IMAG-DLO nota 95-07, Wageningen, Netherlands pp. 35. Stefanowska, J., Ipema, A.H., Hendriks, M.M.W.B., 1999a. The ehaviour of dairy cows in an automatic milking system where selection for milking takes place in the milking stalls. Appl. Anim. Behav. Sci. 62, Stefanowska, J., Tiliopoulos, N.S., Ipema, A.H., Hendriks, M.M.W.B., Dairy cow interactions with an automatic milking system starting with walk-through selection. Appl. Anim. Behav. Sci. 63, Taylor, J., The analysis of designed experiments with censored oservations. Biometrics 29, Tyler, J.W., Fox, L.K., Parish, S.M., Swain, J., Johnson, D.L., Grasseschi, H.A., Gant, R., Effect of feed availaility on post-milking standing time in dairy cows. J. Dairy Sci. 64,