Dairy cow interactions with an automatic milking system starting with `walk-through' selection

Applied Animal Behaviour Science 63 Ž1999. 177–193

Dairy cow interactions with an automatic milking system starting with ‘walk-through’ selection J. Stefanowska a

a,)

, N.S. Tiliopoulos b, A.H. Ipema a , M.M.W.B. Hendriks a

Institute of Agricultural and EnÕironmental Engineering (IMAG-DLO), P.O. Box 43, 6700 AA Wageningen, Netherlands b Department of Life Sciences, A.P. UniÕersity, East Road, CB1 1PT Cambridge, UK Accepted 22 January 1999

Abstract The effects of selecting cows for automatic milking in a passage between the lying and the feeding areas Žso-called ‘walk-through’ selection. on cow behaviour in the Automatic Milking System ŽAMS. were investigated. The same group of 24 cows was subjected in turn to three situations, each lasting 4 weeks: study 1—free cow traffic, study 2—free cow traffic and waiting area for cows selected for milking, study 3—same waiting area as in study 2, but one-way traffic. The average milking frequencies in these studies were respectively 3.0, 2.9, 3.1 milkings per cow per day, with a standard deviation of 0.4 in each study. Cows receiving the ‘milking’ decision were faster in the passage with ‘walk-through’ selection Ž0.17–0.41 mrs. than those receiving the ‘no-milking’ decision Ž0.04–0.09 mrs. Ž p - 0.05.. The latter cows lingered in the passage and urinated there two to three times more frequently than cows given the ‘milking’ decision Ž p - 0.05.. ‘Walk-through’ selection induced specific phenomena such as: withdrawals, unauthorised visits and contacts with selection gate. Cow behaviour in the three above-mentioned situations is discussed. The suggestions for improving the cooperation between the cows and the AMS may help improve cow welfare and should also increase the milking efficiency of the AMS. q 1999 Elsevier Science B.V. All rights reserved. Keywords: Automatic milking systems; ‘Walk-through’ selection; Cattle-milking

1. Introduction The Automatic Milking System ŽAMS. is now functioning well and more than 200 Dutch dairy farmers are using it ŽIpema et al., 1998.. However, one aspect of automatic )

Corresponding author. Tel.: q31-7476450; fax: q31-317425670; e-mail: [email protected]

0168-1591r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 1 5 9 1 Ž 9 9 . 0 0 0 1 2 - X

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J. Stefanowska et al.r Applied Animal BehaÕiour Science 63 (1999) 177–193

milking has not yet been unequivocally solved: cow access to the AMS. This can be organised in various ways, with different consequences. Cows may be brought to the AMS in groups, a method which involves the farmer in extra work. Under this regime, cows must wait in front of the AMS for their turn to be milked ŽSonck, 1996.. In earlier research, ŽStefanowska et al., 1997a. a selection unit was developed in the form of a stall containing a trough for concentrate. This stall provided access to the AMS. When a cow enters the stall, the stall gate closes and a decision is made about whether the cow should be milked. The stall then opens and if the cow was to be milked, she was diverted to the milking stall served by a robot or, if it had been decided that she should not be milked, she was diverted aside. Cows admitted for milking went to the milking stall fast, where the concentrate was given. Cows not admitted for milking lingered in the selection stall ŽStefanowska et al., 1997b., which is why in subsequent research, the selection stall was removed and all cows could freely access the milking stallŽs. and were selected for milking there. Although this solution is technically simpler, the milking stalls of the AMS are burdened by non-milking visits ŽIpema et al., 1997.. An alternative solution is to select cows for milking without closing them in a passage they must often go through during the day. Such a passage must be placed near the milking stalls and it is virtually the entrance to the AMS. The cow is recognised as she walks through the passage and if she should be milked, she can access the milking stall; otherwise, a side gate is opened for her. This selection method is called ‘walkthrough’ selection. The following situations were studied: 1. ‘walk-through’ selection with free traffic of cows in the cowshed, 2. ‘walk-through’ selection, followed by a waiting area for cows selected for milking, with free traffic of cows in the cowshed, 3. ‘walk-through’ selection, followed by a waiting area for cows selected for milking, with one-way traffic of cows in the cowshed Žsolely through the passage with ‘walk-through’ selection.. The sequence of treatments was chosen because it was known that introducing one-way traffic as a first treatment would influence free traffic thereafter, and because it was thought that the waiting area would improve the throughput of the ‘walk-through’ selection. Our hypothesis was that if a cow is not impeded Žstopped. during the selection process, her movement would be promoted. This would contribute to her welfare and by reducing transit time, would increase the AMS efficiency. Because of the novel aspect of selecting the cows while they were moving, special attention was paid to the cow’s reaction to the decision about milking. We sought to identify the factors influencing the different components of the time budget during AMS visits, starting in the passage with ‘walk-through’ selection and ending with the exit from the AMS. 2. Material and methods 2.1. Animals Three studies, each of 4 weeks, were carried out consecutively at the IMAG-DLO experimental farm with the same group of Holstein Friesian cows. Study 1 began with a

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group of 24 cows Žnine primiparous and 15 multiparous.. The mean lactation number was 2.4 Žrange: 1–5.. At the start of study 1, cows were on average 136.9 Žsd s 31.3. days in lactation and were giving on average 31.0 Žsd s 6.9. kg milk a day. When study 1 was completed, one cow Ž4th lactation. was removed; studies 2 and 3 proceeded with 23 cows. At the start of study 2, the cows were on average 171.3 Žsd s 31.8. days in lactation and were giving on average 31.9 Žsd s 8.4. kg of milk a day. At the start of study 3, the cows were on average 199.3 Žsd s 31.8. days in lactation and were giving on average 28.5 Žsd s 6.2. kg of milk a day. 2.2. Housing The cows were kept in a loose housing system with a slatted floor, a lying area with the same number of cubicles as the number of cows, and a separate feeding area with 12 automatic feeders ŽDevir et al., 1996.. There were two watering troughs in the feeding area and one in the lying area. The cows were fed complete diet Žforage and concentrate. ad libitum. Concentrate was also allocated during each automatic milking: 1 kg for heifers, 1.5 kg for older cows. The AMS Ž‘Prolion’ Development, Vijfhuizen, The Netherlands. was situated at one end of the cowshed with its entrance in the lying area and its exit in the feeding area. To get to the AMS area, the cow had to walk through a passage Žsee Fig. 1. in which her transponder was registered by an aerial, she was recognised and the decision about milking was made. She could only be milked if the time interval since the last milking exceeded 6 h; otherwise, she was diverted to the feeding area. At the end of the passage, there was a selection gate that could be in one of two positions: closed to the feeding area and admitting for milking; open to the feeding area and barring access to the milking stalls. The gate’s default position was the position connected to the last visit, e.g., closed if the previous cow had had a ‘milking’ decision, open if that cow had had a ‘no-milking’ decision. The AMS area consisted of the passage with ‘walk-through’ selection, the waiting area Žstudies 2 and 3., double-door gate Žopen, when the milking stalls were unoccupied, entry area, two milking stalls ŽMS1 and MS2. positioned one after the other, passage next to the milking stalls, exit area and one-way exit gate ŽFig. 1.. Milking stalls could be entered and exited from one side. They were equipped with milking clusters, and with mechanical pushers that started to push the cow’s hindquarters when the stall’s exit gate opened. The robot arm moved on a rail along the other side of MS1 and MS2 to attach each of the two milking clusters. The concentrate was offered in the milking stalls in a wheeled trough that moved to the cow, thereby adjusting the length of the milking stall to the size of the cow. After this, the robot arm started to attach the cluster. If attachment failed Žmaximum five attempts during 2 min., the trough returned to its initial position and the exit gate of the milking stall opened. A 100 g portion of concentrate was dispensed before robot attachment started; if attachment failed, no more was dispensed. The AMS was continuously available except during two cleaning periods and back-up of data at midnight. Cows that had not been milked for over 7 h at ‘fetching time’ Ž0730 h and 1930 h. were fetched for milking. The studies differed in the organisation of ‘walk-through’ selection. In study 1, the passage with ‘walk-through’ selection led directly to the double-door gate. In study 2,

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Fig. 1. Layout of the AMS in studies 1, 2, and 3 ŽA—study 1, B—studies 2 and 3.. Dashed lines with arrows indicate possible route through the AMS of a cow arriving in the passage with ‘walk-through’ selection. Asterisks in the passage with ‘walk-through’ selection indicate the location of the aerial. In layout B, cow traffic was free in study 2 but one-way in study 3. In study 3, the one-way gate was placed in the passage on the other side of the cowshed.

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the passage with ‘walk-through’ selection led to the waiting area that was between the passage with ‘walk-through’ selection and the double-door gate. In studies 1 and 2, cows had another two-way passage between the lying and feeding areas at the other end of the cowshed from the AMS. Study 3 used the layout of study 2, but in the two-way passage, there was a one-way gate opening from the feeding area to the lying area. In this way, one-way traffic was created in the cowshed, because the cows could only reach the feeding area by passing through the ‘walk-through’ selection. 2.3. Data collection In all studies, after 2 weeks of habituation to the set-up, cows were observed continuously by three video cameras. One camera was focused on the passage with ‘walk-through’ selection; the second camera was focused on the entry area and MS1, whereas the third camera was focused on MS2 and the exit area. The days for further analysis were chosen from video registrations. Chosen days fulfilled the following conditions: no cows in oestrus and no serious technical disturbances. A total of 4 days Ž24 h. in each study were analysed. These days were spread over 2 weeks of video registration in each study. Data collected through video registration are given in Table 1. The times of execution of different functions of the AMS Že.g., attachment of milking cluster, milking. were registered automatically as well as milk yield and concentrate allotment. Note that, each study was analysed separately according to the following procedures executed on four groups of data ŽI–IV.. 2.3.1. Analysis of time interÕals between two subsequent Õisits to the AMS The effect of the type of visit Žmilking, milking failure, non-milking, withdrawal. on the time interval until the next visit was analysed. It was assumed that the relation between the type of visit and the time interval until the next visit could be described as follows: ysX bqZuq´

Ž 1.

in which b is a vector of fixed effects, u a vector of random effects, X and Z are associated design matrixes and ´ is a vector of random residuals that are not necessarily normally distributed. In this case, it was assumed that variance changed proportional to expected response value. The Generalised Linear Mixed Model ŽGLMM. ŽEngel and Keen, 1994. was used that accounts for increase of variance with increase of response and for possible dependence between repeated observations on the same cows and for a particular cow on the same day. In a GLMM, cows and days are incorporated as random effects. 2.3.2. ArriÕal in the milking stall The response variable is a binary variable Žvoluntary or forced arrival. thus follows a binomial distribution. It was assumed that the relation between probability of forced arrival Ž p . and the factors investigated could be described as follows: log pr Ž 1 y p . s X b q Z u.

Ž 2.

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Table 1 Data obtained from video registration Kind of data

Defintionrdescription

Combinations of the gate position at the end of the passage with ‘walk-through’ selection: ‘MM’, ‘MN’, ‘NM’, ‘NN’ Interaction between the cow and the selection gate

Four combinations of the gate position were possible for the previous and given cow

Times: Ž1. Cow arrives in the passage with ‘walk-through’ selection Ž2. Cow Žadmitted for milking. arrives in the waiting area Žstudies 2 and 3. Ž3. Cow denied milking exited the passage with ‘walk-through’ selection sideways Ž4. Cow arrives in the double-door gate Ž5. Cow arrives in the milking stall Ž6. Cow can leave the milking stall Ž7. Cow has left the milking stall Ž8. Cow has left the AMS Arrival in the milking stall

Defecation and urination As the cow was leaving the milking stall, the presence of other cows was recorded: Ž1. In the exit area Ž2. In the feeding area behind the exit gate of the AMS Aggression between the cow leaving the AMS and other cows in the feeding area Žaggressive behaviour s butting. Types of visits to the AMS: Ž1. Milking visit Ž2. Non-milking visit Žmilking interval shorter than 6 h. Ž3. Milking-failure visit Ž4. Technical problem visit Žnot related to robot.

Ž5. Unauthorised visit

Ž6. Withdrawal visit

Physical contact between the head Žbody. of a cow while the selection gate changed position s collar with transponder passed the aerial sall four hoofs inside the waiting area sall four hoofs behind the gate diverting the cow to the feeding area s head Žup to collar. in that gate s cow enters and stands still sexit gate of milking stall is fully open sall four hoofs outside milking stall sall four hoofs are behind the one-way exit gate of the AMS When a cow entered the milking stall and stood still it was noted Žfrom the video. whether she placed her hind hoofs inside the milking stall voluntarily or whether the closing entrance gate forced her to place them inside Occurrence and place was recorded Answer could be: Ž1. Yes or no Ž2. Yes or no There were four possibilities: no interaction, aggressive behaviour of the exiting cow, mutual aggression, aggressive behaviour of a cow in the feeding area towards the exiting cow ssuccessful milking by robot s cow refused access to a milking stall s robot attachment failed, cow not milked s failure in controlling system, as a result a cow passed alongside the milking stalls or was released from a milking stall without the robot attempting to attach the cluster s cow managed to pass through ‘walk-through’ selection and enter a milking stall Žor feeding area. in spite of ‘no-milking’ Žor ‘milking’. decision s visit to the ‘walk through’ selection followed by cow recognition, decision about the cow, and withdrawal of the cow back to the lying area

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A GLMM was used for this set of data using a logistic link function. The factors investigated were: milking stall Ž1 or 2., type of current and previous visits, time since previous visit and time since previous milking. 2.3.3. Analysis of cows’ rate of moÕement and duration of leaÕing a milking stall Duration of stay in passage with ‘walk-through’ selection, entry area, and exit area was calculated as the difference in registered times taken from the video. The rate of movement in the three above-mentioned compartments of the AMS was calculated as a quotient of duration of the time spent in the compartment and the relevant distance. Additionally, the duration of leaving of the milking stall was calculated. The duration of stay in the waiting area Žstudies 2 and 3. was calculated too, but used only as a possible influential factor, since this duration was sometimes not dependent on cow but on the system Že.g., double-door gate was closed.. It was assumed that the relation between rate of movement Žor duration of leaving of the milking stall. and factors investigated could be described as follows: log Ž y . s X b q Z u q ´

Ž 3.

A Linear Mixed Model ŽLMM. ŽEngel, 1990. was used because variance of response after logarithmic transformation was assumed to be constant and normally distributed. The influence of the following factors was studied: type of visit Žcurrent and previous., time since previous visit, time since previous milking, milking stall Ž1 or 2., amount of concentrate, milk yield, way of arrival, other cows present in exit arearfeeding area. The effects of the factors investigated on response were assumed to be multiplicative and thus, additive on a logarithmic scale. 2.3.4. Defecation and urination during an AMS Õisit The probability of defecation or urination in the passage with ‘walk-through’ selection was analysed in relation to type of visit Žmilking, including milking failure and non-milking. and time spent in the passage. In this analysis, a GLMM was used with a logistic link function for occurrence of defecation or urination Žsee Section 2.3.2, Eq. Ž2... The statistical analyses were executed with the Genstat 5 statistical package ŽGenstat 5 Committee, 1995.. The significance of factors or interactions in all procedures was concluded on the basis of the Wald test ŽRao, 1973..

3. Results 3.1. Structure of the Õisits paid by cows to the AMS The total numbers of visits to the AMS during the 4 chosen days in each study were 703, 703 and 953, respectively in studies 1, 2, and 3. The 953 visits in study 3 comprised all visits to the feeding area, because one-way cow traffic through the AMS was obligatory in this study.

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The distribution of visits to different types and mean number of visits per cow per day in each study are given in Table 2. The average milking frequency was 3.0, 2.9, 3.1 milkings per cow per day in studies 1, 2, 3, with a standard deviation of 0.4 in each study. The number of milking failure visits increased from 0.6 per cow per day in study 1 to 1.2 per cow per day in studies 2 and 3. In all studies combined, the total number of milking failure visits was 281 Ž12% of 2359.. Seven cows contributed to 88% of all visits with milking failure; their teats were less easy for the robot to locate. Visits involving technical problems not related to the robot were exceptional Ž23 cases in all studies together, 1% of all visits.. There were 12 cases of cows passing alongside the milking stalls and 11 cases of cows being released from the milking stall without the robot attempting to attach the cluster. In the AMS with ‘walk-through’ selection, two specific types of visit related to this way of selecting of cows were observed: unauthorised visits Žtotal 50 visits in all studies. and withdrawals Žtotal 130 visits in all studies.; they accounted for 2.1% and 5.5%, respectively of all visits. There were 47 unauthorised visits when cows went through the passage with ‘walk-through’ selection towards the milking stalls in spite of a ‘no-milking’ decision, and there were three unauthorised visits, when cows went through the passage with ‘walk-through’ selection sideways in spite of a ‘milking’ decision. Most unauthorised visits occurred when two cows were standing closely in line in the passage with ‘walk-through’ selection and the selection gate changed position for the second cow and both cows left the passage in the direction defined for the second cow. In some cases, unauthorised visits happened when a cow in the passage with ‘walk-through’ selection was faster than the selection gate. The total number of 130 withdrawals involved 101 withdrawals when the selection gate was in the ‘no-milking’ position and 29 withdrawals when the gate was in the ‘milking’ position. Unauthorised visits and withdrawals were more or less equally divided among cows. In all three studies, both the pattern of visiting the AMS and the different types of visits were more or less equally divided over the day. Cows had to be fetched for milking in circa 4% of all visits Ž8% of milking visits.. Slightly more cows were fetched in the morning Ž57% of all fetching. than during the evening. Fetching was needed because of the rather strict criterion for fetching Ž7 h milking interval. and because some cows had problems with robot attachment Žparticularly in studies 2 and 3.. Fetching proceeded uneventfully: cows approached by a human when in the lying or feeding area walked readily to the AMS.

Table 2 Mean number of visits to the AMS Ž"standard deviation. per cow per day

Study 1 Study 2 Study 3

All

Milking

Non-milking

Milking failure

Technical problems

Unauthorised

Withdrawal

7.3 Ž"3.6. 7.6 Ž"3.9. 10.4 Ž"3.5.

3.0 Ž"0.4. 2.9 Ž"0.4. 3.1 Ž"0.4.

3.0 Ž"2.4. 2.7 Ž"2.3. 5.4 Ž"2.4.

0.6 Ž"0.9. 1.2 Ž"1.8. 1.2 Ž"2.0.

0.1 Ž"0.2. 0.1 Ž"0.1. 0.1 Ž"0.1.

0.1 Ž"0.2. 0.2 Ž"0.2. 0.2 Ž"0.3.

0.5 Ž"0.7. 0.5 Ž"0.6. 0.4 Ž"0.3.

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The type of visit to the AMS had a significant influence on the time interval to the next visit ŽTable 3.. The longest intervals were after milking visits: over 5 h in studies 1 and 2, and over 3 h in study 3. In all studies, cows returned to the AMS soonest after non-milking, milking failure and withdrawal visits. Detailed inspection of time intervals between visits to the AMS revealed that in all studies cows reported to the AMS within 30 min in less than 3% cases after milking visits and in about 40% of cases after milking failure visits. After non-milking visits, cows reported to the AMS within 30 min in about 30% of cases in studies 1 and 2 and in 16% of cases in study 3. 3.2. BehaÕiour of cows in the passage with ‘ walk-through’ selection In the passage with ‘walk-through’ selection, it was observed that during 94 visits Ž4% of all visits; 32, 31, and 31 in studies 1, 2 and 3, respectively., the head or front of a cow came into contact with the selection gate Ž77 cases. or was even momentarily caught in this gate Ž17 cases. ŽFig. 2.. In 49 visits, this happened when the selection gate changed position from ‘milking’ to ‘no-milking’ and barred access to the milking stalls ŽFig. 2A.. In another 39 visits, a cow given a ‘no-milking’ decision lingered, another cow came up behind her and was given a ‘milking’ decision, and the first cow, after contact with the gate changing its position for the second cow, got through to the milking stalls in an unauthorised way ŽFig. 2C.. In a further five cases, a cow moving to the side came in contact with the selection gate that directed her towards milking ŽFig. 2B.. Further, there was only one case in which the cow hesitated to go for milking and came into contact with the gate changing position to ‘no-milking’ for a second cow standing behind ŽFig. 2D.. A total of 38 out of the 94 visits involving impact with the selection gate were unauthorised visits. In Table 4, the effect of position of selection gate on the rate of movement in the passage with ‘walk-through’ selection is given. In study 1, the rate of movement was dependent on the gate’s position after a previous cow: if the selection gate was in the ‘milking’ position, cows approached slower, if it was in the ‘no-milking’ position, cows approached faster. However, this effect was not significant in studies 2 and 3. The type of visit had a statistically significant influence on the rate of movement of cows in the passage in all studies: cows that received a ‘milking’ decision moved faster in the passage than cows with a ‘no-milking’ decision. In study 1, the interaction between previous and current position of the selection gate on the rate of movement was significant. When a cow was given an ‘M’ decision and the selection gate changed for

Table 3 Predicted mean time between visits to the AMS; standard error of mean in parenthesis Time interval Žmin. until the next AMS visit after . . .

Study 1 Study 2 Study 3 a

Milking visit

Non-milking

Milking failure

Withdrawal

332 aa Ž13. 321 a Ž13. 207 a Ž8.

105 c Ž9. 104 bc Ž11. 112 c Ž6.

77 b Ž12. 89 b Ž12. 79 b Ž8.

92 bc Ž13. 124 c Ž16. 88 bc Ž13.

Different letters in one row indicate statistically significant difference Ž p- 0.05..

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Fig. 2. Interactions of cows with selection gate in the passage with ‘walk-through’ selections head Žfront. of a cow came in contact with the selection gate ŽSG. or was momentarily caught in it, when SG changed position. Dashed lines indicate position of selection gate as left after previous visit. Arrows are indicated as follows: ‘black’, direction of movement of selection gate; ‘white’, destination of first cow; ‘shaded’, destination of second cow. Situations: ŽA. cow was ‘too fast’, she should be not milked; ŽB. cow was ‘too fast’, she should be milked; ŽC. first cow lingered, second cow got ‘milking’ decision; ŽD. first cow lingered, second cow got ‘no-milking’ decision.

her from ‘N’ to ‘M’, she was faster than a cow given an ‘M’ decision without the selection gate changing position. When a cow was given an ‘N’ decision, the previous position of gate had no significant effect on her rate of movement. When the selection Table 4 Effect of position of selection gate on predicted rate of movement of cows Žmrs. in the passage with ‘walk-through’ selection; standard error of mean in parenthesis Position of selection gate

Rate of movement Žmrs. Study 1

Position of selection gate after previous cow Position of selection gate for given cow Ž s type of visit for given cow. Interaction: position of selection after previous cow=position of selection gate for given cow a

‘M’s 0.065 aa Ž0.007. ‘N’s 0.100 b Ž0.011. ‘M’s 0.167 a Ž0.027. ‘N’s 0.039 b Ž0.004. ‘MM’s 0.108 a Ž0.014. ‘MN’s 0.039 b Ž0.006. ‘NN’s 0.039 b Ž0.006. ‘NM’s 0.257 c Ž0.038.

Study 2

Study 3

ns b

ns

‘M’s 0.378 a Ž0.040. ‘N’s 0.042 b Ž0.004.

‘M’s 0.411 a Ž0.063. ‘N’s 0.089 b Ž0.008.

ns

ns

‘M’—‘milking’ decision; ‘N’—‘no-milking’ decision; different letters in one column for one variable indicate statistically significant difference Ž p- 0.05.. b Not statistically significant.

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Table 5 The effect of ‘milking’ decision or ‘no-milking’ decision on predicted probability of occurrence of defecation and urination in the passage with ‘walk-through’ selection when duration of time spent there was used as covariable; standard error of mean in parenthesis Probability Decision Study 1 Study 2 Study 3 a b

Defecation a

0.023 a Ž0.005. 0.070 b Ž0.009. ns b

‘Milking’ ‘No-milking’ ‘Milking’ ‘No-milking’ ‘Milking’ ‘No-milking’

ns

Urination 0.066 a Ž0.010. 0.116 b Ž0.018. 0.040 a Ž0.005. 0.106 b Ž0.011. 0.025 a Ž0.004. 0.076 b Ž0.007.

Different letters in one column for each study indicate statistically significant difference Ž p- 0.05.. Not statistically significant.

gate changed position from ‘M’ Žafter previous cow. to ‘N’ Žfor current cow., some cows started to lick themselves. In all three studies, the probability of cows urinating in the passage with ‘walkthrough’ selection was two to three times greater during a non-milking visit than during a milking visit ŽTable 5.. The longer time spent in the passage with ‘walk-through’ selection during a non-milking visit contributed statistically significantly to this. In study 1, cows defecated three times more often during non-milking visits than during milking visits; time spent in the passage was not found to be statistically significant. 3.3. BehaÕiour of cows in the entry area The cows walked faster to MS2 Ž0.42; 0.36; 0.42 Žmrs. in studies 1, 2, 3. than to MS1 Ž0.32, 0.29, 0.34 Žmrs., respectively in studies 1, 2, 3. Ž p - 0.05.. In study 3, the time interval since previous milking influenced the rate of movement in the entry area during the current visit: the longer the interval, the faster the cows. In study 3, moreover, the longer the cows were in the waiting area, the slower their rate of movement in the entry area. This effect was not significant in study 2. In studies 1 and 3, there was a greater probability Ž p - 0.05. that in MS2 arrival would proceed with hind hoofs placed voluntarily inside the milking stall Ž76% cases in

Table 6 Predicted duration of leaving Žs. the milking stall in relation to type of visit; standard error of mean in parenthesis Type of visit

Duration of leaving Žs. Study 1

Milking Milking failure a

a

17 a Ž4. 51 b Ž16.

Study 2

Study 3

18 a Ž4. 45 b Ž11.

14 a Ž4. 50 b Ž23.

Different letters in one column indicate statistically significant difference Ž p- 0.05..

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Table 7 The effect of other cows present in the exit area and in the feeding area on the predicted rate of movement of given cow Žmrs.; standard error of mean in parenthesis Rate of movement Žmrs.

Other cows in the exit area Ž‘yes’r‘no’. Other cows in the feeding area Ž‘yes’r‘no’. a b

Study 1

Study 2

Study 3

ns a

‘no’s 0.037 a Ž0.005. ‘yes’s 0.024 b Ž0.004. ‘no’ s 0.054 a Ž0.007. ‘yes’s 0.016 b Ž0.003.

‘no’s 0.041 a Ž0.007. ‘yes’s 0.018 b Ž0.004. ‘no’ s 0.058 a Ž0.009. ‘yes’s 0.013 b Ž0.004.

‘no’s 0.063 ab Ž0.008. ‘yes’s 0.032 b Ž0.005.

Not statistically significant. Different letters in one column for one variable indicate statistically significant difference Ž p- 0.05..

study 1 and 82% in study 3. in comparison to MS1 Ž67% cases in study 1 and 75% in study 3.. In study 2, this difference between MS1 and MS2 was not statistically significant. 3.4. BehaÕiour of cows in the exit area In all studies, the type of visit had a statistically significant influence on duration of leaving the milking stall: the duration was always shorter in milking visits than in milking failure visits. ŽTable 6.. Portion of concentrate also had a significant effect on duration of leaving in all studies: after larger portions, cows left more quickly. In studies 2 and 3, the presence of one or more cows in the exit area of the AMS reduced the cow’s rate of movement; this effect was not found to be statistically significant in study 1 ŽTable 7.. In all studies, the presence of other cows in the feeding area behind the one-way exit gate of the AMS, decreased the rate of movement of a cow in the exit area. The type of visit or location of milking stall did not affect the rate of movement of cows in the exit area. The presence of other cows in the exit area was observed in 20.1% of visits in study 1, in 15.8% in study 2, and 14.6% in study 3. Instances of other cows in the feeding area blocking the exit of the AMS occurred during 24.4%, 8.6% and 5.5% of visits, respectively in studies 1, 2 and 3. When other cows were present in the feeding area during exiting from the AMS, there was a rather large probability Ž) 50%. of aggression between cows. The aggression between a cow that was leaving and a cow in the feeding area was mutual in 63% of cases; in 33% of cases, it was initiated by a cow that was leaving and in 3% of cases by a cow in the feeding area.

4. Discussion 4.1. ‘Walk-through’ selection One of the reasons for applying ‘walk-through’ selection for milking in the passage between the lying and feeding areas was to solve the ‘old’ problem of cows being

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reluctant to leave the selection stall. We hoped that the lack of an ‘obstacle’ in the form of an enclosing stall would promote the movement of cows through the passage. However, from our findings, it is clear that the problem of cows blocking the passage remains, though it might be less serious than observed in research with a selection stall ŽStefanowska et al., 1997b.. There were some specific consequences related to ‘walkthrough’ selection. First, in all three studies, the rate of movement in the passage was influenced by the decision of the AMS Že.g., position of selection gate.: cows were faster with a ‘milking’ decision and slower with a ‘no-milking’ decision. In study 1, the cows accelerated when the selection gate changed position from ‘no-milking’ to ‘milking’ and their final speed in the passage was faster than cows with a ‘milking’ decision, who arrived in the passage to find the selection gate in the ‘milking’ position after the previous cow. It is possible that the change in the selection gate’s position from ‘no-milking’ to ‘milking’ was an incentive for the cow. However, the effect of previous position of selection gate on the rate of movement of a given cow was found to be not significant in studies 2 and 3, possibly because in these studies there was a waiting area, where cows sometimes had to wait for access to the milking stall. This probably made it less easy for cows in the passage to have insight into the access to a milking stall. Self-licking when the selection gate closed access to the milking stall was observed in all studies and is probably a sign of frustration at being denied access. It is known that opiates released during e.g., licking help relieve frustration ŽZanella et al., 1996.. Cows modified their strategy in some way in relation to ‘walk-through’ selection. Some withdrew from the passage; this mostly happened when the selection gate directed them sideways after a ‘no-milking’ decision. Some cows that came to the passage to find the selection gate in a ‘milking’ position after the previous cow, went through faster and sometimes they reached the milking stalls in an unauthorised way or they came into contact with the selection gate. Cows that were directed sideways often lingered and urinated in the passage more often than cows directed for milking. In some cases, they managed to reach the milking stalls in an unauthorised way, when the next cow was given a ‘milking’ decision and both proceeded together. The possibility that a cow directed sideways deliberately lingered and waited for a cow with a ‘milking’ decision cannot be excluded. We are uneasy about possible collisions between the cows and the selection gate, as these may frighten or even hurt the cow, especially if she is moving at the time. However, contacts with the gate occurred during only 4% Ž94 cases. of all visits, and in only 17 out of the 94 cases, were cows momentarily caught in the selection gate. 4.2. Time budget in the AMS Locating the AMS between the lying and the feeding areas and always giving concentrate during milking creates a purpose-oriented movement, related to feed resources ŽPirkelmann, 1992; Ipema, 1997.. Motivation related to milking is not sufficient to ensure voluntary reporting to the AMS ŽPrescott, 1997.. In study 3 with one-way traffic, the interval between milking and return to the AMS was 2 h shorter on average than in studies 1 and 2 without one-way traffic. In studies 1 and 2, cows could go to the feeding area first through another Žunimpeded. passage before they revisited the AMS, whereas in study 3 they had to go through the AMS to reach the feeding area.

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In order to maximise milking efficiency, time spent in the AMS Žnot related to milking. should be as short as possible. However, the cow’s own speed Žwithout human supervision. is much slower than the farmer would like. Quick Ž1978. reported that the entry time of cows to a rotary milking parlour was longer when the operator worked inside the ring than when the operator worked outside the ring and could encourage cows to move forward. According to Winter and Hillerton Ž1995., if cows are allowed to report to the AMS voluntarily, it must be accepted that they will do so at their own pace. Prescott Ž1996. mentioned the following factors as being crucial in determining how fast cows move through the AMS: stopping, uncertainty, presentation of food reward, insight into surroundings and other reasons such as: escape from aggressive attention of other cows, health, age and curiosity. We found that compared with the walking speed of cattle Ž1 mrs. ŽPhillips, 1993. the rate of movement of cows in the AMS was slow Žon average: up to 0.4 mrs in the passage with ‘walk-through’ selection for milking visits, up to 0.4 mrs in the entry area, less than 0.1 mrs in the exit area.. In the passage with ‘walk-through’ selection, the rate of movement was always faster in milking visits than in non-milking visits. The rate of movement in the entry area was slower when cows spent more time in the waiting area, e.g., when they had to wait because the double-door gate was closed. This result supports the contention of Prescott Ž1997. that rapidity of cows in an AMS is influenced negatively by stopping. Movement was faster when cows were directed to MS2. This finding confirmed earlier results ŽStefanowska et al., 1999.. Moving forward seems to be easier for a cow than having to turn during arrival to MS1. The other possible explanation is that a faster movement can be developed over a somewhat longer distance than over a short distance. In studies 1 and 3, there was a greater probability that cows using MS2 would arrive ‘properly’ Žhind hoofs placed inside the milking stall voluntarily.. The reason that no significant effect was found in study 2 was probably because MS2 was used somewhat less in that study than in studies 1 and 3. Cows with milking failure lingered in the milking stall. It is probable that withdrawing the trough for concentrate and opening the exit gate of the milking stall frustrates a cow in such a way that she refuses to leave for some time in spite of being pushed. The rate of movement in the exit area was influenced by other cows present there or other cows obstructing the one-way exit gate from the side of the feeding area. This confirmed the results of earlier research on cows selected for milking in the milking stalls ŽStefanowska et al., 1999.. However, the proportion of visits with a blocked exit and aggressive interactions in these three studies was remarkably lower than in the research cited above. The greater incidence of obstruction and aggression is probably attributable to the non-milking visits that were routed through milking stalls in this research. Cows that had to leave the AMS without any reward were probably unclear about the outcome of their visits, were therefore more aggressive and also congregated more at the exit of the AMS. 4.3. Cow welfare The welfare of cows during an AMS visit should be judged in the context of whether or not experiences related to automatic milking are pleasant ŽHurnik, 1994.. Being

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denied access to the milking stalls, especially if the selection gate is visibly in the ‘milking’ position after a previous cow, can be seen as a disincentive. Collisions with the selection gate will cause fear andror uncertainty. The relatively large frequency of urination in the passage with ‘walk-through’ selection during non-milking visits and self-licking undertaken after stopping in front of the selection gate that denied access to milking stalls seem to confirm this. It is striking that frequency of urination in the AMS was equal to or even higher than frequency of defecation, even though various authors have reported that cows defecate twice as often as they urinate ŽHafez, 1969; Hidari et al., 1982; Suzuki et al., 1983.. It is possible that the AMS creates some uncertainty andror fear in a cow, influencing her eliminative behaviour. Kilgour and Albright Ž1971. suggested that during stress, cows could be stimulated to defecate and urinate. In earlier research, it was observed that cows refused milking Žand concentrate. when selected for milking in the milking stall, urinated more often after leaving the milking stall than cows that were milked ŽStefanowska et al., 1999.. The effect of experiences in the AMS on eliminative behaviour is difficult to study and interpret, since the probability of defecation Žurination. is related to duration of time spent in the AMS and this is influenced by type of visit. The kind of behaviour that precedes the visit to the AMS Žlying, feeding. may influence the occurrence of defecationrurination as well. Special attention should be paid to milking failure visits, which accounted for 12% of all visits. The cows involved sometimes paid several repeat visits to the AMS in close succession. On working farms such cows are channelled off into a separate area immediately, or after a second milking failure. In our research, it was decided a priori that these cows would not be fetched for milking before ‘fetching’ time. It can be surmised that these cows returned because they did not finish their portion andror they wanted more concentrate. It is also possible that cows returned because they wanted or expected to be milked. The problem of milking failure in the context of welfare needs to be investigated in a separate experiment. It is evident that cows in the AMS are hindered by bends. Turning sideways during non-milking visits is probably additionally inconvenient for a cow: not only is she refused access to a milking stall, she must also turn in order to exit. Some of the problems described here might be more serious if the AMS has to cope with more cows than we used in this research. 4.4. Optimisation of the AMS with ‘ walk-through’ selection Although, in general, the AMS with ‘walk-through’ selection functioned sufficiently to achieve the intended milking frequency, we identified some problems that may affect cow welfare. In our opinion, solving these problems will not only improve cow welfare in the AMS with ‘walk-through’ selection, but will also improve the milking efficiency of the AMS. Continuity of the flow of cows through the AMS should be stimulated in a positive, attractive way. If a cow is refused milking, she should nonetheless be rewarded for visiting the AMS, for instance, by being given a small portion of concentrate after leaving the selection place Že.g., in the feeding area.. A drawback is that this could encourage extra movement through the selection place. Devir Ž1995. proposed denying this concentrate reinforcement to animals that return to the AMS too often.

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Another proposal concerns the positioning of the passage with ‘walk-through’ selection in the cowshed and the default position of selection gate. The passage with ‘walk-through’ selection should be located in such a way that cows moving through it between the lying and feeding areas proceed in a straight line. This is especially important for one-way traffic, when all cow traffic to the feeding area must go through this passage and only a small part of traffic must be directed towards milking stalls. The selection gate should always stand in the default ‘no-milking’ position, directing cows towards the feeding area. This can help prevent ‘too fast’ cows from contact with the gate and it avoids cows being confused by being confronted with a gate that changes position from ‘milking’ to ‘no-milking’. The functioning of selection gate should be improved so that it does not change position for a ‘second’ cow if the ‘first’ cow is still in the passage. Awkward turns should be always avoided, but if they are technically unavoidable, it is better for a cow to turn towards a milking stall Žand concentrate.. Additionally, changing the position of selection gate from ‘no-milking’ to ‘milking’ will give a cow an incentive to go further. This will speed up the rate of movement and encourage cows to enter the milking stall properly Žhind hoofs placed inside voluntarily.. Cows can be encouraged to leave the exit area of the AMS more quickly by giving a reward Žconcentrate. in the feeding area. The concentrate dispenser giving the ultimate reward for visits to the AMS should be sited away from the exit of the AMS, to prevent cows from congregating there and becoming aggressive.

5. Conclusions Ž1. The AMS extended with ‘walk-through’ selection induced specific phenomena in cows in the passage with ‘walk-through’ selection, such as: change in rate of movement, withdrawals, contacts with selection gate, unauthorised visits. Ž2. Optimising the AMS with ‘walk-through’ selection, in terms of where the passage with ‘walk-through’ selection is sited in relation to milking stalls and default position of selection gate, will improve cow welfare and milking efficiency. Ž3. In the light of the evidence that cows develop their own strategy in the AMS, further attention should be paid to investigating cows’ experiences in the AMS, and especially to the feasibility of improving of the cow’s cooperation in the AMS.

Acknowledgements The authors wish to thank Prof. Dr. P.R. Wiepkema for his perceptive comments on the ethological aspects of this paper.

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