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The effect of age at tethering on behaviour of heifer calves
APPLIED ANIMAL BEHAVIOUR SCIENCE
Applied Animal Behaviour
Science 43
( 1995) 227-238
The effect of age at tethering on behaviour of heifer calves Margit Bak Jensen National Institute of Animal Science, P.O. Box 39, DK-8830 Tjele, Denmark Accepted 8
February 1995
Abstract The aims of the study were to investigate the behavioural consequences of tethering and to investigate the behavioural changes after tethering in calves of two different age groups. Thirty-six Danish Black and White heifer calves were housed in individual pens from birth. Eighteen of the calves were tethered in individual stalls at 12 weeks of age, and 18 calves were tethered at 23 weeks of age. The calves assigned to late tethering were housed in groups of three in deep litter pens from 12 to 23 weeks of age. From 24 h video recordings, collected in the first, second, fourth and eighth weeks after tethering in all calves, and in the eighth weeks after grouping in calves assigned to late tethering, the behaviour of individual calves was recorded instantaneously at 5 min intervals. In addition, the number of lying periods was counted. At the same age (i.e. 8 weeks after tethering and grouping, respectively) tethered calves spent more time lying down (62% vs. 56%, P
Grooming
behaviour;
Oral behaviour; Tethering
0168-1591/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDIO168-1591(95)00567-6
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M.B. Jensen /Applied
Animal Behaviour Science 43 (1995) 227-238
1. Introduction Tethering in stalls with a hard floor surface has been found to inhibit the normal pattern of lying down in growing cattle. For instance, a lower number of lying periods and a higher frequency of lying intentions have been found in heifers and fattening bulls tethered in stalls with partially slatted concrete floor, compared with control animals kept untethered on deep litter. These differences in resting behaviour, which were observed during the first week after tethering, were also observed after 3 months of tethering in heifers (Mtiller et al., 1989)) and after 1 month of tethering in bulls (Ladewig and Smidt, 1989). However, it is difficult to assess the change in behaviour after tethering in these investigations, as behaviour was only measured on two occasions. Tethering after a period of grazing has been found to induce high levels of abnormal oral behaviour, which increased during the first 4 weeks after tethering in heifers (Redbo, 1993)) and during the first 3 weeks in dairy cows (Redbo, 1992). However, the transfer from pasture to tie-stalls included a change of feed and this may have affected the development of abnormal oral behaviour in these studies. Investigations of the behavioural consequences of tethering have concentrated on cows, heifers and growing bulls. Although the tethering of calves 2-3 months of age is common practice in Scandinavia and North America, studies on the behavioural consequences of tethering of calves are few. In Denmark, the tethering of calves under the age of 6 months is prohibited by recent legislation (Regulation no. 999, 1993), and group housing of calves from weaning to 6 months of age is strongly recommended. It is, however, questionable whether tethering of 6 month old calves has less severe behavioural consequences than tethering of 2-3 month old calves. As behaviour may depend on age, an assessment of the effect of age has to be based on change in behaviour over time, rather than the level of behaviour at one particular time. Repeated measurements of behaviour after tethering allow assessment of the change in behaviour after tethering. By relating the change in behaviour after tethering to age at tethering, it may be assessed whether animals of different age groups respond differently or similarly to tethering. The objectives of this study were to investigate the behavioural consequences of tethering in calves offered the same feed, and to relate the changes in behaviour after tethering to age at tethering.
2. Material and methods 2.1. Animals, housing and feeding Thirty-six Danish Black and White heifer calves were used. All calves were separated from their dams at birth, housed individually in straw bedded pens (2.2 m* per animal) and offered their dam’s colostrum ad libitum twice a day for the first 4 days after birth. As the calves were used in an earlier experiment investigating the effect of milk feeding regime on behaviour during the first 12 weeks of age, the calves were blocked by birth order and assigned to one of two milk feeding regimes from the fifth day after birth until weaning at 42 days of age: either 4.6 1 of milk per day or milk ad libitum, offered twice a day. All
M.B. Jensen /Applied Animal Behaviour Science 43 (1995) 227-238
1*2”d +“--.
4* I_...__~ ~._~
229
8m weeks after tethering 1~ .---__._ Tag--.-_----‘Emz I
8”’ week after grouping m
single box group box
._I tie-stall Fig. 1, Housing of the calves of the two age groups and plan for the observations. The top line represents housing and observations of the calves tethered at 12 weeks of age, the bottom line represents housing and observations of the calves tethered at 23 weeks of age.
calves were offered 1 kg concentrate per day from the fifth day after birth until they reached 125 kg liveweight. From birth to weaning all calves were offered hay ad libitum, and from weaning all calves were offered roughage ad libitum. Eighteen calves (born in the autumn 1992) were assigned to tethering at 23 weeks of age (hereafter referred to as old calves) and 18 calves (born in the winter 1992/1993) were assigned to tethering at 12 weeks of age (young calves). Calves assigned to tethering at 23 weeks of age were tethered from 16 February 1993 to 1 March 1993, and calves assigned to tethering at 12 weeks of age were tethered from 19 January 1993 to 21 April 1993. Thus, the period in which observations after tethering were made on the calves assigned to late tethering overlapped the period in which observations after tethering were made on the calves assigned to early tethering. The 18 calves assigned to early tethering were moved directly from the individual pens and tethered in individual stalls at 12 weeks (mean & SD 85.5 f 2.5 days) of age. At tethering the animals weighed on average 96 + 12 kg. The tethers were double chain tethers, and the individual stalls were 0.9 m wide. The floor was solid concrete in the front part of the stalls, while the rear was concrete slats. The length of the stalls was adjusted as the calves grew, and the calves were always standing with their hind legs on the slats. The 18 calves assigned to late tethering were housed in groups of three calves in 5.4 m* pens with deep litter from 12 to 23 weeks ( 16147.7 days) of age where these calves were also tethered in individual stalls of the same type as described above. At tethering these calves weighed on average 148 f 11 kg. Housing of the calves of the two age groups is shown in Fig. 1. 2.2. Behavioural observations The behaviour of all calves was video recorded during the first 24 h of tethering and during 24 h on days 7,21 and 49 after tethering, denoted the first, second, fourth and eighth weeks after tethering, respectively. In addition, the behaviour of the 18 calves assigned to
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M.B. Jensen /Applied Animal Behuviour Science 43 (1995) 227-238
Table 1 Description of the postural and behavioural categories recorded Posture
Standing
Body supported by all four legs
Lying head raised Lying head on body Lying other head positions
Lying on the side, head raised on a stretched neck Lying on side, head turned down the side and resting on body Lying on side, head resting on the fixtures or on the floor
Behaviour
Feeding Ruminating Investigating floor Licking fixtures Biting fixtures Grooming behaviour No activity
Feeding from feed manger with muzzle in the feed or chewing food with head raised over the feed manger Chewing regurgitated feed Sniffing the floor Licking the partitions of the feed manger, the bars or the chain (tongue out of mouth) Holding the partition of the feed manger, the bar or the chain in the mouth, accompanied by chewing movements Licking itself or scratching itself with a hindleg or against the fixtures Immobile, no apparent activity
late tethering was video recorded during 24 h on day 49 after grouping, denoted the eighth week after grouping. This observation before tethering was made for comparison between behaviour of tethered and group housed calves at the same age. The experimental procedure is depicted schematically in Fig. 1. From each 24 h video recording the body posture and behaviour of individual calves were recorded instantaneously at 5 min intervals (time sampling). In addition, the number of lying periods was counted. The behavioural categories used were mutually exclusive and are defined in Table 1.
2.3. Statistical analysis
For each individual calf the number of lying periods and the percentage of observations spent in each of the behavioural categories were calculated separately for each of the sampling times.
2.3.1. Behaviour of tethered and group housed calves at the same age In the comparison between the behaviour of tethered and group housed calves at the same age (i.e. in the eighth week after tethering and grouping, respectively), behaviour which was normally distributed was analysed by a two-way analysis of variance with housing and earlier milk feeding as main effects. Behaviour which was not normally distributed (except the number of lying periods) was analysed by a Wilcoxon-Mann-Whitney test for differences between age groups and earlier feeding treatments (Siegel and Castellan, 1988). The number of lying periods was analysed by an appropriate generalised linear model, more specifically a Poisson model.
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Animal Behaviour Science 43 (1995) 227-238
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2.3.2. Behaviour of calves of the two age groups in the$rst, second, fourth and eighth weeks after tethering The behaviour of calves of the two age groups in the first, second, fourth and eighth weeks after tethering was analysed by profile analysis for two independent groups (Morrison, 1976)) where data were assumed multivariate normally distributed (i.e. percentage of observations lying, lying with the head raised, lying with head resting on the body, feeding and ruminating). To assess the assumption of multivariate normal distribution, each marginal distribution was tested for normality. Significant effect of earlier milk feeding, and significant interaction between earlier milk feeding and week after tethering were not found for any of these variables, therefore the factor earlier milk feeding was subsequently excluded from the profile analysis (but not the other analyses). The four observations on each individual are assumed to be given by a multivariate normal distribution
i= 1,2 k= 1,...,18 where, Xilk, Xjzk, Xi3k and X,, are the four observations on the kth calf in the ith age group, and pi4 are the four mean responses of the ith age group, Pill Pi29 Pi3 2 a,,...,flz=Var(X. rlk ) ,...,Var(X&, and Ujj=Cov(X,ik, Xv,). Note that the covariance does not depend on age group, or animal. The null hypothesis of no age group by week interaction tests if differences between successive observations on the two age groups are different, i.e. if the profiles are parallel
where C is the 3 X 4 profile transformation matrix, and I_Li(i = 1,2) is a vector with the four mean responses for treatment group i. If the null hypothesis of no age group by week interaction is accepted, the null hypothesis of equal levels on the age groups may be tested. This hypothesis tests if the profiles overlap, equivalently if the sum of the means of each age group are different
HO: j’p, = j’p2 where j’ is the four component vector with unity in each position. Finally, also if the null hypothesis of no age group by week interaction is accepted, the null hypothesis of equal response means (no week effect) may be tested. This hypothesis tests if the changes between successive observations are different from zero
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Table 2 Behaviourof tetheredand group housed calves at 20 weeks of age. Percentageof observations(mean f SEM) Tethered
Lying periods Lying, total Lying head raised Lying head on body Ruminating
P-value
Grouphoused
Mean
SEM
Mean
SEM
9.8 61.8 52.2 8.0 34.7
0.7 1.5 1.3 0.7 1.4
10.8 56.0 45.6 7.8 28.7
0.3 0.9 1.0 0.7 1.1
NS 0.01 0.001 NS 0.01
Ho: C(p, +/_lQ) =o
Contrasts were made between successive weeks after tethering. Contrasts were made separately for the two age groups where significant age group by week interactions were found. Behavioural categories for which the data were not marginally normally distributed and could not be assumed multivariate normally distributed (i.e. number of lying periods, standing investigating floor, licking fixtures, biting fixtures and grooming behaviour) were analysed using non-parametric statistical methods. Friedman two-way analysis of variance by ranks was used to analyse the effect of week after tethering within each age group and each earlier milk feeding treatment. The Wilcoxon-Mann-Whitney test was used to analyse for differences between age groups and earlier milk feeding treatment (Siegel and Castellan, 1988).
3. Results 3.1. Behaviour of tethered and group housed calves at the same age In the eighth week after respectively tethering and grouping, tethered calves spent more time lying down, and lay with their head raised more than group housed calves. In addition, tethered calves spent more time ruminating than group housed calves. There was no effect of housing on lying with head resting on body, and the number of lying periods was similar in tethered and group housed calves (Table 2). As shown in Table 3, tethered calves were biting the fixtures more often, and performed grooming behaviour more often than group housed calves. No effect of housing was found on the level of licking fixtures or investigating the floor. No significant interactions between housing and earlier milk feeding were found for any of the behavioural categories. However, calves fed milk ad libitum until 42 days of age spent less time resting the head on the body (mean f SEM, 6.7 f 0.6% vs. 9.1 f 0.7%, Fc1,32j=7.55, P
M.B. Jensen /Applied Animal Behaviour Science 43 (1995) 227-238
233
Table 3 Behaviour of tethered and group housed calves at 20 weeks of age (median and range) Group housed
Tethered
Licking fixtures Biting fixtures Grooming behaviour Investigating floor
P-value
Median
Range
Median
Range
0.7 0.7 2.8 1.0
o.tH.5 0.0-3.8 0.7-5.9 0.3-3.8
1.o 0.0 1.9 1.6
0.0-2.8 0.047 0.7-3.5 0.4-3.5
NS 0.001 0.01 NS
3.2. Behaviour of calves of the two age groups in the3rst, second, fourth and eighth weeks after tethering Successive observations of total time spent lying, and time spent lying with the head raised or resting on the body, are shown in Fig. 2. Different profiles in the two age groups (i.e. age group by week interactions) were found of total lying and lying with head raised (Table 4). In the old calves, total lying and lying with head raised increased throughout the 8 weeks after tethering, while total lying and lying with head raised only increased from the first to second weeks after tethering in the young calves (Table 5). The profiles of lying with head resting on body did not differ between the two age groups, but the group level tended to be higher in the young group of calves (Table 4), There was an effect of week on lying with head resting on body (Table 4)) due to an increase from the first to the second weeks (Table 5). With respect to ruminating, the profiles of the two age groups did not differ, and age group levels were similar. However, there was an effect of week after tethering (Table 4), as the level increased from the first to the second week (Table 5). Feeding showed no age group by week interaction and no effect of week, but the level of feeding was higher in the old calves (Table 4). Successive observations of lying periods, standing investigating floor, licking fixtures and grooming behaviour are shown in Fig. 3. The number of lying periods increased with Lying (% of obs.) 80
1
0 4 1 2 Weeks after tethering
8
Fig. 2. Percentage of observations (mean) in which calves were lying, including lying with the head raised, or resting on the body in first, second, fourth, and eighth weeks after tethering in calves tethered at 12 and 23 weeks of age.
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M.B. Jensen /Applied Animal Behaviour Science 43 (1995) 227-238
Table 4 Results of the profile analysis. F-values and significance levels. Interaction and main effects ’ Behaviour
Group-Week
Lying total
F3,32= 7.13
Lying head raised
F3.32= 6.77
Lying head body
Group
Week
F3.32= 2.42
F,,34 = 4.95
F3,32= 16.44
(P=O.O84) F3.32= 1.82 (P=O.163) F3.32= 2.23 (P=O.104)
(P=O.O33) F ,,34= 0.12 (P=O.736) F 1.34= 11.39 (P=O.O02)
(P
Ruminating Feeding
(P
(P
1.24
(P=O.312)
a Note that main effects are only tested where no significant interaction between group and week was found.
weeks after tethering in the old calves (Friedman, F,,, = 32.52, P < 0.001)) but not in the young calves. Standing investigating the floor decreased in both the young (Friedman, F,,, = 26.97, P < 0.001) and the old calves (Friedman, PC,, = 40.05, P < 0.001). Licking of the fixtures was affected by week after tethering in the old calves (Friedman, FC3)=20.7, P
Lying head raised Young calves Old calves
Lying head body All calves
Ruminating All calves
Weeks 1-2
Weeks 24
Weeks 4-8
F,,,,=26.07 (P
F1.,,=
0.90 (P=O.357) F ,.,7= 13.71 (P=O.O02)
F,,,,=0.94 (P=O.347) F,,,,=8.16 (P=O.Oll)
F,,,, = 13.94 (P=O.O02) F,,,, = 24.70
F,.17= 1.11 (P=O.307) F ,.,,= 9.26
F,,,, = 0.07 (P=O.791) F ,,,,=6.29
(P
(P=O.O07)
(P=O.O23)
F r.,=21.16
F ,,s=
(P
1.68 (P=O.204)
F,,34=6.17 (P=O.O18)
F ,.M= 14.94 (P
F ,.%=0.67 (P=O.417)
F ,.~=3.32 (P=O.O77)
’ Reported for groups separately where significant group by week interaction was found.
M.B. Jensen /Applied Animal Behaviour Science 43 (1995) 227-238
Number
Stat-d. investigating 12
of lying bouts
Weeks after tethering
floor (% of ohs.)
Weeks after Grooming 12
Licking fixtures (% of ohs.)
235
tethering
behav. (% of obs)
10 6 6 4 2
a
ab B
b b
a
0L 12
4 Weeks after tethering
6
b I>
1
4 2 Weeks after tethering
8
Fig. 3. Number of lying periods (median) and percentage of observations (median) in which calves were.standing investigating the floor, licking the fixtures and performing grooming behaviour in the first, second, fourth, and eighth weeks after tethering in calves tethered at 12 and 23 weeks of age. Significant differences between weeks within age groups are indicated by different letters.
two early milk feeding treatments the measured variables.
with respect to effects of week after tethering for any of
4. Discussion 4. I. Behaviour of tethered and group housed calves at the same age Tethered calves did not appear to have any problems changing position at 20 weeks of age compared with group housed calves, as neither the number of lying periods nor standing investigation the floor was affected by housing. Investigation of the floor is a normal behaviour preceding lying down in cattle; the behaviour indicates that the animal intends to lie down. A high frequency of floor investigations indicates that the animal is hesitant to lie down because lying down is difficult or even painful (Miiller et al., 1989). Problems in changing position appear to depend on the animal’s age. In agreement with the results of the present study on 20 week old calves, Dellmeier et al. ( 1985) found no effect of tethering on the number of lying periods in 5 week old calves. In contrast, tethered 20 month old heifers (Mtiller et al., 1989), and tethered 14 month old growing bulls (Ladewig and Smidt, 1989) showed fewer lying periods and more lying intentions than controls kept untethered on deep litter. It appears that cattle experience problems in changing position in a tie-stall when they are above the age of the calves used in the present comparison.
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In this experiment the duration of lying was lower in group-housed calves than in tethered calves. This may be due to the space allowance used in the group pens. Concurrently, de Wilt ( 1986) found that 9-21 week old calves in small group pens ( 1.5 m* per calf) lay down less than calves in individual pens, while similar levels of lying down were found in a large group yard (3.6 m* per calf) and in individual stalls, pens and hutches in 5 week old calves (Dellmeier et al., 1985). The lower lying time in the group housed calves in the study by de Wilt ( 1986) and in this study, may be due to low space allowances. It may be that only at high space allowances will the lying time be as high as in tethered animals. Tethered calves ruminated more than loose housed calves. In dairy cows, reduced rumination as well as reduced lying, were seen as a result of low space allowances (C&o, 1978)) and the differences found in rumination may be explained by the differences in lying time. Tethered calves groomed themselves more than group housed calves. The tethered calves did not have the same opportunity to groom each other as group housed calves, and the tethered calves may have been unable to groom all parts of their body satisfactory, which may have caused them to groom themselves more. However, as pointed out by Simonsen ( 1979), the grooming behaviour of cattle may reflect displacement activities. Higher frequencies of grooming have been reported in tethered dairy cows (Krohn, 1994) and in calves kept in individual pens (Kerr and Wood-Gush, 1987) compared with controls kept loose on pasture. Displacement activities may occur as a result of mutual inhibition of conflicting tendencies, or as a result of frustration due to thwarting of one behaviour. If grooming does occur as a result of thwarting, it seems that thwarting of several activities may cause displacement grooming in tethered cattle. For instance, both deprivation of lying and social isolation increased the frequency and duration of grooming in dairy cows (Munksgaard, 1994). With regard to the function of displacement grooming, it has been suggested that it may function as a de-arousing activity in situations with behavioural conflict or stress (Spruijt et al., 1992). Tethering also induced a higher level of biting fixtures, but not licking fixtures. An increase in these oral behaviours, which are normally associated with direct exploration, has earlier been associated with restrictive environments in calves (Webster et al., 1985; Kerr and Wood-Gush, 1987). Tethering after a period of grazing has been found to induce high levels of abnormal oral behaviour (tongue rolling and biting fixtures) in heifers (Redbo, 1992) and cows (Redbo, 1993). In these studies the animals were fed roughage restrictively when tethered and the change in feed may have affected the development of abnormal oral behaviour. In the present study all animals were offered the same feed ration ad libitum, and only biting fixtures was affected by tethering. The increased level of biting fixtures in tethered calves may be caused by either restriction of movement, inhibition of social behaviour or inhibition of appetitive feeding behaviour. 4.2. Behuviour of calves of the two age groups in thejirst, second, fourth and eighth weeks afer tethering In the first week of tethering, all calves showed hesitation in lying down, as standing investigating the floor was much higher in the first week of tethering than in later weeks in both age groups. However, problems in changing position indicated by an initial low number of lying periods, were only observed in the old calves. During the weeks after tethering, the
M.B. Jensen /Applied Animal Behaviour Science 43 (1995) 227-238
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number of lying periods increased in the old calves, suggesting that they gradually got used to changing position in the tie-stalls. According to the number of lying periods, the young calves did not appear to have any problems lying down or getting up for the first 8 weeks after tethering. Pougin ( 1982) studied the behavioural response to a slatted floor in cattle of different ages. Generally, introduction to the slatted floor resulted in hesitation in lying down, fewer lying periods and shorter lying time. However, animals resumed their normal resting behaviour more rapidly when introduced to the slatted floor at 3 and 6 months of age than at 9 months of age. This suggests that younger animals adapt more rapidly with respect to changing position, and support the suggestion that problems in changing position increase as the animals get older. The duration of lying down increased markedly from the first to the second week after tethering. This initial trend was similar in young and old calves, and illustrates that some of the immediate decrease in the duration of lying down at tethering was regained by all calves. An immediate decrease in duration of lying down at tethering may be due to either hesitance to lie down in the new environment, or uncomfortable lying positions in the tether. In the old group of calves, problems with changing position may have caused the old group of calves to lie down less in the first couple of weeks after tethering. Lying with the head raised showed the same trend as the total duration of lying, but lying with the head resting on the body increased from the first to the second week in both age groups. This is best explained by calves learning to place the body far back in the stalls, enabling them to rest the head on their body. Calves tethered at 12 weeks did not increase the duration of lying down after the second week, while the duration of lying down increased throughout the weeks in calves tethered at 23 weeks. The level of ruminating increased during the first week of tethering in both age groups, and this trend presumably reflects the concurrent increase in lying time. A initial decrease in lying down at tethering may well have resulted in a decrease in rumination. Two types of oral behaviour directed towards the fixtures were recorded: licking fixtures and biting fixtures. Licking fixtures decreased over the weeks, while biting fixtures was unaffected by weeks after tethering in both groups. Licking fixtures may be a normal exploratory behaviour, which would be expected to decrease with time in the new environment. As discussed earlier, biting fixtures may be an abnormal behaviour induced by tethering. Trends after tethering were not different in the two age groups and the overall level did not differ between age groups. Tethering thus appears to affect both age groups equally with respect to development of this abnormal oral behaviour. The level of grooming behaviour increased over the weeks in both age groups. As mentioned earlier, a higher level of grooming behaviour in the tethered animals may reflect displacement behaviour. Also with respect to this behaviour both age groups were equally affected by the tethering. In conclusion, the results on resting behaviour suggest that calves tethered at a late age have more initial problems changing position in the tie-stall, and suffer a reduction in lying time for longer than calves tethered at an early age. The results on biting fixtures and grooming behaviour do not suggest any dependence of age at tethering. In addition to prohibiting the tethering of young calves, the question of tethering of older animals (including growing and mature cattle) should also come under consideration. Acknowledgements Hans Kiers Foundation and The Danish Research Academy have funded Margit Bak Jensen. The statistical advice of Flemming Skjoth and Rodrigo Labouriou, and the technical
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assistance of Erik L. Decker and Gynter Nielsen is highly appreciated. Thanks also to Klaus Vestergaard, Chr. C. Krohn, Lene Munksgaard and Lene Juul Pedersen for useful suggestions on the experiment.
References Czako, J., 1978. The effect of space on the behaviour and production of dairy cows in large-scale systems. First
World Congress on Ethology applied to Zootechnics, 23-27 October, Madrid, Industras Graficas Espana, Madrid, pp. 275-283. Dellmeier, G.R., Friend, T.H. and Gbur, E.E., 1985.Comparison of four methods ofcalf confinement. II. Behaviour. J. Anim. Sci., 60: 1102-l 109. De Wilt, J.G., 1986. Behaviour of veal calves in individual crates and in group pens. Neth. J. Agric. Sci., 34: 233235. Kerr, S.G.C. and Wood-Gush, D.G.M., 1987. A comparison of the early behaviour of intensively and extensively reared calves. Anim. Prod., 45: 181-190. Krohn, C.C., 1994. Behaviour of dairy cows kept in extensive (loose housing/pasture) or intensive (tie stall) environments. III. Grooming, exploration and abnormal behaviour. Appl. Anim. Behav. Sci., in press. Ladewig, J. and Smidt, D., 1989. Behavior, episodic secretion of cortisol, and adrenocortical reactivity in bulls subjected to tethering. Harm. Behav., 23: 344-360. Morrison, D.F., 1976. Multivariate Statistical Methods. McGraw-Hill, New York, 338 pp. Milller, C., Ladewig, J., Thielscher, H.H. and Smidt, D., 1989. Behaviour and heart rate of heifers housed in tether stanchions without straw. Physiol. Behav., 46: 751-754. Munksgaard, L., 1994. Methods for assessment of stress in cattle; behaviour, pituitary-adrenal-reactivity and growth hormone concentration. Ph.D. Thesis, Royal Veterinary and Agricultural University, Denmark, 42 pp. Pougin, M., 1982. On assessing adaptation of young cattle to keeping on slatted floor by means of behaviour patterns as also changes in claws and serum enzymes. Thesis, Bonn University, Germany, 137 pp, Redbo, I., 1992. The influence of restraint on the occurrence of oral stereotypies in dairy cows. Appl. Anim. Behav. Sci., 35: 115-123. Redbo, I., 1993. Stereotypies and cortisol secretion in heifers subjected to tethering. Appl. Anim. Behav. Sci., 38: 213-225. Regulation no. 999. Protection of calves. Danish Ministry of Justice, 14 December 1993, 3 pp. Siegel, S. and Castellan, N.J., 1988. Nonparametric Statistics for the Behavioural Sciences, 2nd edn. McGrawHill, New York, 399 pp. Simonsen, H.B., 1979. Grooming behaviour of domestic cattle. Nord. Vet.-Med., 31: l-5. Spruijt, B.M., van Hooff, J.A.R.A.M. and Gispen, W.H., 1992. Ethologyand neurobiologyofgroomingbehaviour. Physiol. Rev., 72: 825-852. Webster, A.J.F., Saville, C., Church, B.M., Gnanasakthy, A. and Moss, R., 1985. The effect of different rearing systems on the development of calf behaviour. Br. Vet. J., 141: 249-264.
Applied Animal Behaviour
Science 43
( 1995) 227-238
The effect of age at tethering on behaviour of heifer calves Margit Bak Jensen National Institute of Animal Science, P.O. Box 39, DK-8830 Tjele, Denmark Accepted 8
February 1995
Abstract The aims of the study were to investigate the behavioural consequences of tethering and to investigate the behavioural changes after tethering in calves of two different age groups. Thirty-six Danish Black and White heifer calves were housed in individual pens from birth. Eighteen of the calves were tethered in individual stalls at 12 weeks of age, and 18 calves were tethered at 23 weeks of age. The calves assigned to late tethering were housed in groups of three in deep litter pens from 12 to 23 weeks of age. From 24 h video recordings, collected in the first, second, fourth and eighth weeks after tethering in all calves, and in the eighth weeks after grouping in calves assigned to late tethering, the behaviour of individual calves was recorded instantaneously at 5 min intervals. In addition, the number of lying periods was counted. At the same age (i.e. 8 weeks after tethering and grouping, respectively) tethered calves spent more time lying down (62% vs. 56%, P
Grooming
behaviour;
Oral behaviour; Tethering
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Animal Behaviour Science 43 (1995) 227-238
1. Introduction Tethering in stalls with a hard floor surface has been found to inhibit the normal pattern of lying down in growing cattle. For instance, a lower number of lying periods and a higher frequency of lying intentions have been found in heifers and fattening bulls tethered in stalls with partially slatted concrete floor, compared with control animals kept untethered on deep litter. These differences in resting behaviour, which were observed during the first week after tethering, were also observed after 3 months of tethering in heifers (Mtiller et al., 1989)) and after 1 month of tethering in bulls (Ladewig and Smidt, 1989). However, it is difficult to assess the change in behaviour after tethering in these investigations, as behaviour was only measured on two occasions. Tethering after a period of grazing has been found to induce high levels of abnormal oral behaviour, which increased during the first 4 weeks after tethering in heifers (Redbo, 1993)) and during the first 3 weeks in dairy cows (Redbo, 1992). However, the transfer from pasture to tie-stalls included a change of feed and this may have affected the development of abnormal oral behaviour in these studies. Investigations of the behavioural consequences of tethering have concentrated on cows, heifers and growing bulls. Although the tethering of calves 2-3 months of age is common practice in Scandinavia and North America, studies on the behavioural consequences of tethering of calves are few. In Denmark, the tethering of calves under the age of 6 months is prohibited by recent legislation (Regulation no. 999, 1993), and group housing of calves from weaning to 6 months of age is strongly recommended. It is, however, questionable whether tethering of 6 month old calves has less severe behavioural consequences than tethering of 2-3 month old calves. As behaviour may depend on age, an assessment of the effect of age has to be based on change in behaviour over time, rather than the level of behaviour at one particular time. Repeated measurements of behaviour after tethering allow assessment of the change in behaviour after tethering. By relating the change in behaviour after tethering to age at tethering, it may be assessed whether animals of different age groups respond differently or similarly to tethering. The objectives of this study were to investigate the behavioural consequences of tethering in calves offered the same feed, and to relate the changes in behaviour after tethering to age at tethering.
2. Material and methods 2.1. Animals, housing and feeding Thirty-six Danish Black and White heifer calves were used. All calves were separated from their dams at birth, housed individually in straw bedded pens (2.2 m* per animal) and offered their dam’s colostrum ad libitum twice a day for the first 4 days after birth. As the calves were used in an earlier experiment investigating the effect of milk feeding regime on behaviour during the first 12 weeks of age, the calves were blocked by birth order and assigned to one of two milk feeding regimes from the fifth day after birth until weaning at 42 days of age: either 4.6 1 of milk per day or milk ad libitum, offered twice a day. All
M.B. Jensen /Applied Animal Behaviour Science 43 (1995) 227-238
1*2”d +“--.
4* I_...__~ ~._~
229
8m weeks after tethering 1~ .---__._ Tag--.-_----‘Emz I
8”’ week after grouping m
single box group box
._I tie-stall Fig. 1, Housing of the calves of the two age groups and plan for the observations. The top line represents housing and observations of the calves tethered at 12 weeks of age, the bottom line represents housing and observations of the calves tethered at 23 weeks of age.
calves were offered 1 kg concentrate per day from the fifth day after birth until they reached 125 kg liveweight. From birth to weaning all calves were offered hay ad libitum, and from weaning all calves were offered roughage ad libitum. Eighteen calves (born in the autumn 1992) were assigned to tethering at 23 weeks of age (hereafter referred to as old calves) and 18 calves (born in the winter 1992/1993) were assigned to tethering at 12 weeks of age (young calves). Calves assigned to tethering at 23 weeks of age were tethered from 16 February 1993 to 1 March 1993, and calves assigned to tethering at 12 weeks of age were tethered from 19 January 1993 to 21 April 1993. Thus, the period in which observations after tethering were made on the calves assigned to late tethering overlapped the period in which observations after tethering were made on the calves assigned to early tethering. The 18 calves assigned to early tethering were moved directly from the individual pens and tethered in individual stalls at 12 weeks (mean & SD 85.5 f 2.5 days) of age. At tethering the animals weighed on average 96 + 12 kg. The tethers were double chain tethers, and the individual stalls were 0.9 m wide. The floor was solid concrete in the front part of the stalls, while the rear was concrete slats. The length of the stalls was adjusted as the calves grew, and the calves were always standing with their hind legs on the slats. The 18 calves assigned to late tethering were housed in groups of three calves in 5.4 m* pens with deep litter from 12 to 23 weeks ( 16147.7 days) of age where these calves were also tethered in individual stalls of the same type as described above. At tethering these calves weighed on average 148 f 11 kg. Housing of the calves of the two age groups is shown in Fig. 1. 2.2. Behavioural observations The behaviour of all calves was video recorded during the first 24 h of tethering and during 24 h on days 7,21 and 49 after tethering, denoted the first, second, fourth and eighth weeks after tethering, respectively. In addition, the behaviour of the 18 calves assigned to
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Table 1 Description of the postural and behavioural categories recorded Posture
Standing
Body supported by all four legs
Lying head raised Lying head on body Lying other head positions
Lying on the side, head raised on a stretched neck Lying on side, head turned down the side and resting on body Lying on side, head resting on the fixtures or on the floor
Behaviour
Feeding Ruminating Investigating floor Licking fixtures Biting fixtures Grooming behaviour No activity
Feeding from feed manger with muzzle in the feed or chewing food with head raised over the feed manger Chewing regurgitated feed Sniffing the floor Licking the partitions of the feed manger, the bars or the chain (tongue out of mouth) Holding the partition of the feed manger, the bar or the chain in the mouth, accompanied by chewing movements Licking itself or scratching itself with a hindleg or against the fixtures Immobile, no apparent activity
late tethering was video recorded during 24 h on day 49 after grouping, denoted the eighth week after grouping. This observation before tethering was made for comparison between behaviour of tethered and group housed calves at the same age. The experimental procedure is depicted schematically in Fig. 1. From each 24 h video recording the body posture and behaviour of individual calves were recorded instantaneously at 5 min intervals (time sampling). In addition, the number of lying periods was counted. The behavioural categories used were mutually exclusive and are defined in Table 1.
2.3. Statistical analysis
For each individual calf the number of lying periods and the percentage of observations spent in each of the behavioural categories were calculated separately for each of the sampling times.
2.3.1. Behaviour of tethered and group housed calves at the same age In the comparison between the behaviour of tethered and group housed calves at the same age (i.e. in the eighth week after tethering and grouping, respectively), behaviour which was normally distributed was analysed by a two-way analysis of variance with housing and earlier milk feeding as main effects. Behaviour which was not normally distributed (except the number of lying periods) was analysed by a Wilcoxon-Mann-Whitney test for differences between age groups and earlier feeding treatments (Siegel and Castellan, 1988). The number of lying periods was analysed by an appropriate generalised linear model, more specifically a Poisson model.
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2.3.2. Behaviour of calves of the two age groups in the$rst, second, fourth and eighth weeks after tethering The behaviour of calves of the two age groups in the first, second, fourth and eighth weeks after tethering was analysed by profile analysis for two independent groups (Morrison, 1976)) where data were assumed multivariate normally distributed (i.e. percentage of observations lying, lying with the head raised, lying with head resting on the body, feeding and ruminating). To assess the assumption of multivariate normal distribution, each marginal distribution was tested for normality. Significant effect of earlier milk feeding, and significant interaction between earlier milk feeding and week after tethering were not found for any of these variables, therefore the factor earlier milk feeding was subsequently excluded from the profile analysis (but not the other analyses). The four observations on each individual are assumed to be given by a multivariate normal distribution
i= 1,2 k= 1,...,18 where, Xilk, Xjzk, Xi3k and X,, are the four observations on the kth calf in the ith age group, and pi4 are the four mean responses of the ith age group, Pill Pi29 Pi3 2 a,,...,flz=Var(X. rlk ) ,...,Var(X&, and Ujj=Cov(X,ik, Xv,). Note that the covariance does not depend on age group, or animal. The null hypothesis of no age group by week interaction tests if differences between successive observations on the two age groups are different, i.e. if the profiles are parallel
where C is the 3 X 4 profile transformation matrix, and I_Li(i = 1,2) is a vector with the four mean responses for treatment group i. If the null hypothesis of no age group by week interaction is accepted, the null hypothesis of equal levels on the age groups may be tested. This hypothesis tests if the profiles overlap, equivalently if the sum of the means of each age group are different
HO: j’p, = j’p2 where j’ is the four component vector with unity in each position. Finally, also if the null hypothesis of no age group by week interaction is accepted, the null hypothesis of equal response means (no week effect) may be tested. This hypothesis tests if the changes between successive observations are different from zero
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Table 2 Behaviourof tetheredand group housed calves at 20 weeks of age. Percentageof observations(mean f SEM) Tethered
Lying periods Lying, total Lying head raised Lying head on body Ruminating
P-value
Grouphoused
Mean
SEM
Mean
SEM
9.8 61.8 52.2 8.0 34.7
0.7 1.5 1.3 0.7 1.4
10.8 56.0 45.6 7.8 28.7
0.3 0.9 1.0 0.7 1.1
NS 0.01 0.001 NS 0.01
Ho: C(p, +/_lQ) =o
Contrasts were made between successive weeks after tethering. Contrasts were made separately for the two age groups where significant age group by week interactions were found. Behavioural categories for which the data were not marginally normally distributed and could not be assumed multivariate normally distributed (i.e. number of lying periods, standing investigating floor, licking fixtures, biting fixtures and grooming behaviour) were analysed using non-parametric statistical methods. Friedman two-way analysis of variance by ranks was used to analyse the effect of week after tethering within each age group and each earlier milk feeding treatment. The Wilcoxon-Mann-Whitney test was used to analyse for differences between age groups and earlier milk feeding treatment (Siegel and Castellan, 1988).
3. Results 3.1. Behaviour of tethered and group housed calves at the same age In the eighth week after respectively tethering and grouping, tethered calves spent more time lying down, and lay with their head raised more than group housed calves. In addition, tethered calves spent more time ruminating than group housed calves. There was no effect of housing on lying with head resting on body, and the number of lying periods was similar in tethered and group housed calves (Table 2). As shown in Table 3, tethered calves were biting the fixtures more often, and performed grooming behaviour more often than group housed calves. No effect of housing was found on the level of licking fixtures or investigating the floor. No significant interactions between housing and earlier milk feeding were found for any of the behavioural categories. However, calves fed milk ad libitum until 42 days of age spent less time resting the head on the body (mean f SEM, 6.7 f 0.6% vs. 9.1 f 0.7%, Fc1,32j=7.55, P
M.B. Jensen /Applied Animal Behaviour Science 43 (1995) 227-238
233
Table 3 Behaviour of tethered and group housed calves at 20 weeks of age (median and range) Group housed
Tethered
Licking fixtures Biting fixtures Grooming behaviour Investigating floor
P-value
Median
Range
Median
Range
0.7 0.7 2.8 1.0
o.tH.5 0.0-3.8 0.7-5.9 0.3-3.8
1.o 0.0 1.9 1.6
0.0-2.8 0.047 0.7-3.5 0.4-3.5
NS 0.001 0.01 NS
3.2. Behaviour of calves of the two age groups in the3rst, second, fourth and eighth weeks after tethering Successive observations of total time spent lying, and time spent lying with the head raised or resting on the body, are shown in Fig. 2. Different profiles in the two age groups (i.e. age group by week interactions) were found of total lying and lying with head raised (Table 4). In the old calves, total lying and lying with head raised increased throughout the 8 weeks after tethering, while total lying and lying with head raised only increased from the first to second weeks after tethering in the young calves (Table 5). The profiles of lying with head resting on body did not differ between the two age groups, but the group level tended to be higher in the young group of calves (Table 4), There was an effect of week on lying with head resting on body (Table 4)) due to an increase from the first to the second weeks (Table 5). With respect to ruminating, the profiles of the two age groups did not differ, and age group levels were similar. However, there was an effect of week after tethering (Table 4), as the level increased from the first to the second week (Table 5). Feeding showed no age group by week interaction and no effect of week, but the level of feeding was higher in the old calves (Table 4). Successive observations of lying periods, standing investigating floor, licking fixtures and grooming behaviour are shown in Fig. 3. The number of lying periods increased with Lying (% of obs.) 80
1
0 4 1 2 Weeks after tethering
8
Fig. 2. Percentage of observations (mean) in which calves were lying, including lying with the head raised, or resting on the body in first, second, fourth, and eighth weeks after tethering in calves tethered at 12 and 23 weeks of age.
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Table 4 Results of the profile analysis. F-values and significance levels. Interaction and main effects ’ Behaviour
Group-Week
Lying total
F3,32= 7.13
Lying head raised
F3.32= 6.77
Lying head body
Group
Week
F3.32= 2.42
F,,34 = 4.95
F3,32= 16.44
(P=O.O84) F3.32= 1.82 (P=O.163) F3.32= 2.23 (P=O.104)
(P=O.O33) F ,,34= 0.12 (P=O.736) F 1.34= 11.39 (P=O.O02)
(P
Ruminating Feeding
(P
(P
1.24
(P=O.312)
a Note that main effects are only tested where no significant interaction between group and week was found.
weeks after tethering in the old calves (Friedman, F,,, = 32.52, P < 0.001)) but not in the young calves. Standing investigating the floor decreased in both the young (Friedman, F,,, = 26.97, P < 0.001) and the old calves (Friedman, PC,, = 40.05, P < 0.001). Licking of the fixtures was affected by week after tethering in the old calves (Friedman, FC3)=20.7, P
Lying head raised Young calves Old calves
Lying head body All calves
Ruminating All calves
Weeks 1-2
Weeks 24
Weeks 4-8
F,,,,=26.07 (P
F1.,,=
0.90 (P=O.357) F ,.,7= 13.71 (P=O.O02)
F,,,,=0.94 (P=O.347) F,,,,=8.16 (P=O.Oll)
F,,,, = 13.94 (P=O.O02) F,,,, = 24.70
F,.17= 1.11 (P=O.307) F ,.,,= 9.26
F,,,, = 0.07 (P=O.791) F ,,,,=6.29
(P
(P=O.O07)
(P=O.O23)
F r.,=21.16
F ,,s=
(P
1.68 (P=O.204)
F,,34=6.17 (P=O.O18)
F ,.M= 14.94 (P
F ,.%=0.67 (P=O.417)
F ,.~=3.32 (P=O.O77)
’ Reported for groups separately where significant group by week interaction was found.
M.B. Jensen /Applied Animal Behaviour Science 43 (1995) 227-238
Number
Stat-d. investigating 12
of lying bouts
Weeks after tethering
floor (% of ohs.)
Weeks after Grooming 12
Licking fixtures (% of ohs.)
235
tethering
behav. (% of obs)
10 6 6 4 2
a
ab B
b b
a
0L 12
4 Weeks after tethering
6
b I>
1
4 2 Weeks after tethering
8
Fig. 3. Number of lying periods (median) and percentage of observations (median) in which calves were.standing investigating the floor, licking the fixtures and performing grooming behaviour in the first, second, fourth, and eighth weeks after tethering in calves tethered at 12 and 23 weeks of age. Significant differences between weeks within age groups are indicated by different letters.
two early milk feeding treatments the measured variables.
with respect to effects of week after tethering for any of
4. Discussion 4. I. Behaviour of tethered and group housed calves at the same age Tethered calves did not appear to have any problems changing position at 20 weeks of age compared with group housed calves, as neither the number of lying periods nor standing investigation the floor was affected by housing. Investigation of the floor is a normal behaviour preceding lying down in cattle; the behaviour indicates that the animal intends to lie down. A high frequency of floor investigations indicates that the animal is hesitant to lie down because lying down is difficult or even painful (Miiller et al., 1989). Problems in changing position appear to depend on the animal’s age. In agreement with the results of the present study on 20 week old calves, Dellmeier et al. ( 1985) found no effect of tethering on the number of lying periods in 5 week old calves. In contrast, tethered 20 month old heifers (Mtiller et al., 1989), and tethered 14 month old growing bulls (Ladewig and Smidt, 1989) showed fewer lying periods and more lying intentions than controls kept untethered on deep litter. It appears that cattle experience problems in changing position in a tie-stall when they are above the age of the calves used in the present comparison.
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In this experiment the duration of lying was lower in group-housed calves than in tethered calves. This may be due to the space allowance used in the group pens. Concurrently, de Wilt ( 1986) found that 9-21 week old calves in small group pens ( 1.5 m* per calf) lay down less than calves in individual pens, while similar levels of lying down were found in a large group yard (3.6 m* per calf) and in individual stalls, pens and hutches in 5 week old calves (Dellmeier et al., 1985). The lower lying time in the group housed calves in the study by de Wilt ( 1986) and in this study, may be due to low space allowances. It may be that only at high space allowances will the lying time be as high as in tethered animals. Tethered calves ruminated more than loose housed calves. In dairy cows, reduced rumination as well as reduced lying, were seen as a result of low space allowances (C&o, 1978)) and the differences found in rumination may be explained by the differences in lying time. Tethered calves groomed themselves more than group housed calves. The tethered calves did not have the same opportunity to groom each other as group housed calves, and the tethered calves may have been unable to groom all parts of their body satisfactory, which may have caused them to groom themselves more. However, as pointed out by Simonsen ( 1979), the grooming behaviour of cattle may reflect displacement activities. Higher frequencies of grooming have been reported in tethered dairy cows (Krohn, 1994) and in calves kept in individual pens (Kerr and Wood-Gush, 1987) compared with controls kept loose on pasture. Displacement activities may occur as a result of mutual inhibition of conflicting tendencies, or as a result of frustration due to thwarting of one behaviour. If grooming does occur as a result of thwarting, it seems that thwarting of several activities may cause displacement grooming in tethered cattle. For instance, both deprivation of lying and social isolation increased the frequency and duration of grooming in dairy cows (Munksgaard, 1994). With regard to the function of displacement grooming, it has been suggested that it may function as a de-arousing activity in situations with behavioural conflict or stress (Spruijt et al., 1992). Tethering also induced a higher level of biting fixtures, but not licking fixtures. An increase in these oral behaviours, which are normally associated with direct exploration, has earlier been associated with restrictive environments in calves (Webster et al., 1985; Kerr and Wood-Gush, 1987). Tethering after a period of grazing has been found to induce high levels of abnormal oral behaviour (tongue rolling and biting fixtures) in heifers (Redbo, 1992) and cows (Redbo, 1993). In these studies the animals were fed roughage restrictively when tethered and the change in feed may have affected the development of abnormal oral behaviour. In the present study all animals were offered the same feed ration ad libitum, and only biting fixtures was affected by tethering. The increased level of biting fixtures in tethered calves may be caused by either restriction of movement, inhibition of social behaviour or inhibition of appetitive feeding behaviour. 4.2. Behuviour of calves of the two age groups in thejirst, second, fourth and eighth weeks afer tethering In the first week of tethering, all calves showed hesitation in lying down, as standing investigating the floor was much higher in the first week of tethering than in later weeks in both age groups. However, problems in changing position indicated by an initial low number of lying periods, were only observed in the old calves. During the weeks after tethering, the
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number of lying periods increased in the old calves, suggesting that they gradually got used to changing position in the tie-stalls. According to the number of lying periods, the young calves did not appear to have any problems lying down or getting up for the first 8 weeks after tethering. Pougin ( 1982) studied the behavioural response to a slatted floor in cattle of different ages. Generally, introduction to the slatted floor resulted in hesitation in lying down, fewer lying periods and shorter lying time. However, animals resumed their normal resting behaviour more rapidly when introduced to the slatted floor at 3 and 6 months of age than at 9 months of age. This suggests that younger animals adapt more rapidly with respect to changing position, and support the suggestion that problems in changing position increase as the animals get older. The duration of lying down increased markedly from the first to the second week after tethering. This initial trend was similar in young and old calves, and illustrates that some of the immediate decrease in the duration of lying down at tethering was regained by all calves. An immediate decrease in duration of lying down at tethering may be due to either hesitance to lie down in the new environment, or uncomfortable lying positions in the tether. In the old group of calves, problems with changing position may have caused the old group of calves to lie down less in the first couple of weeks after tethering. Lying with the head raised showed the same trend as the total duration of lying, but lying with the head resting on the body increased from the first to the second week in both age groups. This is best explained by calves learning to place the body far back in the stalls, enabling them to rest the head on their body. Calves tethered at 12 weeks did not increase the duration of lying down after the second week, while the duration of lying down increased throughout the weeks in calves tethered at 23 weeks. The level of ruminating increased during the first week of tethering in both age groups, and this trend presumably reflects the concurrent increase in lying time. A initial decrease in lying down at tethering may well have resulted in a decrease in rumination. Two types of oral behaviour directed towards the fixtures were recorded: licking fixtures and biting fixtures. Licking fixtures decreased over the weeks, while biting fixtures was unaffected by weeks after tethering in both groups. Licking fixtures may be a normal exploratory behaviour, which would be expected to decrease with time in the new environment. As discussed earlier, biting fixtures may be an abnormal behaviour induced by tethering. Trends after tethering were not different in the two age groups and the overall level did not differ between age groups. Tethering thus appears to affect both age groups equally with respect to development of this abnormal oral behaviour. The level of grooming behaviour increased over the weeks in both age groups. As mentioned earlier, a higher level of grooming behaviour in the tethered animals may reflect displacement behaviour. Also with respect to this behaviour both age groups were equally affected by the tethering. In conclusion, the results on resting behaviour suggest that calves tethered at a late age have more initial problems changing position in the tie-stall, and suffer a reduction in lying time for longer than calves tethered at an early age. The results on biting fixtures and grooming behaviour do not suggest any dependence of age at tethering. In addition to prohibiting the tethering of young calves, the question of tethering of older animals (including growing and mature cattle) should also come under consideration. Acknowledgements Hans Kiers Foundation and The Danish Research Academy have funded Margit Bak Jensen. The statistical advice of Flemming Skjoth and Rodrigo Labouriou, and the technical
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assistance of Erik L. Decker and Gynter Nielsen is highly appreciated. Thanks also to Klaus Vestergaard, Chr. C. Krohn, Lene Munksgaard and Lene Juul Pedersen for useful suggestions on the experiment.
References Czako, J., 1978. The effect of space on the behaviour and production of dairy cows in large-scale systems. First
World Congress on Ethology applied to Zootechnics, 23-27 October, Madrid, Industras Graficas Espana, Madrid, pp. 275-283. Dellmeier, G.R., Friend, T.H. and Gbur, E.E., 1985.Comparison of four methods ofcalf confinement. II. Behaviour. J. Anim. Sci., 60: 1102-l 109. De Wilt, J.G., 1986. Behaviour of veal calves in individual crates and in group pens. Neth. J. Agric. Sci., 34: 233235. Kerr, S.G.C. and Wood-Gush, D.G.M., 1987. A comparison of the early behaviour of intensively and extensively reared calves. Anim. Prod., 45: 181-190. Krohn, C.C., 1994. Behaviour of dairy cows kept in extensive (loose housing/pasture) or intensive (tie stall) environments. III. Grooming, exploration and abnormal behaviour. Appl. Anim. Behav. Sci., in press. Ladewig, J. and Smidt, D., 1989. Behavior, episodic secretion of cortisol, and adrenocortical reactivity in bulls subjected to tethering. Harm. Behav., 23: 344-360. Morrison, D.F., 1976. Multivariate Statistical Methods. McGraw-Hill, New York, 338 pp. Milller, C., Ladewig, J., Thielscher, H.H. and Smidt, D., 1989. Behaviour and heart rate of heifers housed in tether stanchions without straw. Physiol. Behav., 46: 751-754. Munksgaard, L., 1994. Methods for assessment of stress in cattle; behaviour, pituitary-adrenal-reactivity and growth hormone concentration. Ph.D. Thesis, Royal Veterinary and Agricultural University, Denmark, 42 pp. Pougin, M., 1982. On assessing adaptation of young cattle to keeping on slatted floor by means of behaviour patterns as also changes in claws and serum enzymes. Thesis, Bonn University, Germany, 137 pp, Redbo, I., 1992. The influence of restraint on the occurrence of oral stereotypies in dairy cows. Appl. Anim. Behav. Sci., 35: 115-123. Redbo, I., 1993. Stereotypies and cortisol secretion in heifers subjected to tethering. Appl. Anim. Behav. Sci., 38: 213-225. Regulation no. 999. Protection of calves. Danish Ministry of Justice, 14 December 1993, 3 pp. Siegel, S. and Castellan, N.J., 1988. Nonparametric Statistics for the Behavioural Sciences, 2nd edn. McGrawHill, New York, 399 pp. Simonsen, H.B., 1979. Grooming behaviour of domestic cattle. Nord. Vet.-Med., 31: l-5. Spruijt, B.M., van Hooff, J.A.R.A.M. and Gispen, W.H., 1992. Ethologyand neurobiologyofgroomingbehaviour. Physiol. Rev., 72: 825-852. Webster, A.J.F., Saville, C., Church, B.M., Gnanasakthy, A. and Moss, R., 1985. The effect of different rearing systems on the development of calf behaviour. Br. Vet. J., 141: 249-264.