Research in Veterinary Science 1994, 56, 8-17
Effect of different methods of castration on behaviour and plasma cortisol in calves of three ages I. S. ROBERTSON, Department of Veterinary Clinical Studies, J. E. KENT, V. MOLONY, Department of Preclinical Sciences, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Summerhall, Edinburgh EH9 1QH
Calves of six, 21 and 42 days were either handled (controls) or castrated by Burdizzo, by surgical or by rubber ring techniques and their behaviour and plasma cortisol monitored for three hours after treatment. The rubber ring caused significant increases in active behaviour and abnormal postures for two hours compared with handled or castrated by Burdizzo and surgical techniques, and surgical techniques resulted in a significant increase in abnormal standing, particularly in the first 30 minutes. Abnormal behaviour and posture were recorded less frequently in six-day-old calves. The mean cortisol peaks for six-, 21- and 42-day-old calves were, respectively, 36, 31 and 23 nmol litre -1 in the handled groups; 60, 43 and 48 nmol litre -1 in the rubber ring groups; 77, 50 and 62 nmol litre -1 in t h e Burdizzo groups; and 106, 63 and 107 nmol litre -1 in the surgical groups. The greatest cortisol response occurred in 42-day-old surgically treated calves and the shortest response after Burdizzo castration. These responses suggest that irrespective of age, all methods of castration studied caused acute pain. Burdizzo castration appeared to produce the least pain, particularly in younger calves. CHANGES in behaviour and plasma cortisol have been used by Molony et al (1993) and Kent et al (1993) to assess the pain associated with the age and method of castration and tail docking of lambs. These methods have been extended for the study of castration in calves by including changes in active behaviour such as foot stamping and tail wagging. The monitoring of abnormal behaviour and posture immediately after castration has not been
widely used to assess pain or distress in calves. A study by Mellor et al (1991) using rubber rings in calves less than one week old showed little response in either behaviour or plasma cortisol. Earlier work by Macauley and Friend (1987a,b) in older calves included some observations on cantering, standing and kicking, which, with plasma cortisol concentration (pcc) responses, led to the conclusion that surgical castration was more painful than either chemical or Burdizzo methods. Fell et al (1986) included observations of behaviour to help quantify pain or distress arising from surgical or rubber ring castration of four- to 11week-old calves. They concluded that the latter method was the least painful, mainly because of the lower salivary cortisol values recorded after this method. Plasma cortisol estimations have been used in a number of reports to assess pain and stress in animals including the comparison of different methods of castration in seven- to nine-month-old catfie (Cohen et al 1990) and the effects of transportation on different aged calves (Kent and Ewbank 1983, 1986a,b). This paper reports the behavioural and plasma cortisol responses of calves castrated by Burdizzo, surgery or rubber ring at six, 21 and 42 days old.
Materials and methods Ayrshire bull calves were obtained over a fourweek period directly from a local farm, two or three days after birth. To reduce potential stress, the calves continued to be fed on the same proprietary cold milk substitute solution (Milkivit Quicksilver; BP Nutrition) as they had been fed from birth. The milk feed (maximum 10 litre per calf per day), given before 09.00, was provided by
Castration of calves a self-feed teat system. Hay, concentrate ration and water were also available freely. All the calves were penned in multiples immediately after removal from the dam at 12 to 24 hours after birth and in pairs for three to 17 days before castration. They were allotted to treatments at random, except that an adjustment on the basis of liveweight was made to keep group mean bodyweights similar. The experimental design consisted of a 3 x 4 comparison (group n=5) with handling only (control) or castration at three ages, six, 21 and 42 days old, at mean weights of 37, 47.5 and 57.1 kg, respectively, by Burdizzo, surgery and rubber ring. All the castrations were conducted between 09.30 and 10.00 British summer time to minimise the effect of diurnal variation in plasma cortisol of calves (Gardy-Godillot et al 1989). No anaesthetic agent was administered to any of the calves. All the calves were turned and held in a sitting position, in or just outside their pen, by one operator while a second performed the castration or handling procedure. All castrations were performed by the same operator. The surgical and rubber ring procedures were as described for lambs (Molony et al 1993). Castration by Burdizzo was performed by crushing, through intact skin, the spermatic cord of each testis in turn, once for 10 seconds, using clamps with a 45 mm blade x 225 mm lever for six-day-olds and 60 m m x 330 mm for older calves. The control calves were turned to a sitting position and held there for two minutes. The maximum time for surgery was seven minutes and for the rubber ring and Burdizzo techniques less than two minutes.
Behavioural assessment Continuous recordings of calf activities (active behaviours) were made for 180 minutes after castration with observations of posture recorded every two minutes for 96 minutes and every six minutes for a further 84 minutes. The behaviours recorded were as follows.
Restlessness score. The number of times a calf partly or fully stood up and lay down was scored; standing up and lying down were recorded as one action.
Foot stamping. One action was recorded when either a front or hindleg was lifted and forcefully placed on the ground.
9
Tail wagging. Tail movement from side to side was recorded as one action; a continuous series of movements was also recorded as one action. Interference from flies was kept to a minimum through the regular use of insecticide sprays.
Head turning. This was interpreted as the head turned to a point on the body beyond the shoulder; it included grooming.
Eating. The time spent sucking milk from the teat, chewing hay or straw, or eating the concentrate ration was noted.
Ruminating. Ruminating behaviour was observed in 21- and 42-day-old calves after castration but with inconclusive results due to the low incidence and intermittent nature of the behaviour in young calves. The postures observed were as described for lambs (Molony et al 1993) except that lateral lying (LL) was not subdivided and ventral (sternal) recumbency was only divided into three types: all legs folded under the body with head down (V1), head up (V 2) or full or partial extension of the hindlegs (V3). Standing was divided into three types: walking, eating, playing or standing with no obvious abnormality (S1), unsteady abnormal posture or gait, standing stationary with no movement of the legs or the body, sometimes with a hunched back and trembling, standing with the hindlegs stretched back ($2), or as for S2 but with persistent kicking and foot stamping, walking backwards, resting or walking on knees or falling over occasionally ($3). Postures V 3, LL, S 2 and S 3 were classified as abnormal since they were rarely adopted by control calves. All behavioural recordings were started as soon as the calves had returned, after treatment, to a standing position in their pen.
Blood sampling Samples were taken from each calf by jugular venepuncture at 20 minutes and one minute before castration, and then at 12 minute intervals for 96 minutes and at 138 minutes and 180 minutes after treatment. A modified enzyme immunoassay technique (Serono Serozyme Cortisol kits, Woking) was
10
I. S. Robertson, J. E. Kent, V. Molony
used to measure plasma cortisol (Kent et al 1993), using bovine plasma as quality control samples. Statistical analysis
A two-way analysis of variance (behaviour) and covariance (cortisol) was conducted with significant differences between groups established after use of t tables and the standard error of difference (SED). Two calves (surgical and rubber ring, 21 days) were removed from the statistical analysis due to illness and two because of cortisol or behavioural responses that were so extreme that their results would have grossly distorted the mean in groups with such small numbers. One control calf (six days) with normal behaviour had the highest cortisol peak (185 nmol litre-1) of all calves when it was unintentionally frustrated because a period of teat sucking 12 minutes after treatment was interrupted for blood sampling. The other calf, castrated by Burdizzo (42 days) had a six- to sevenfold increase above all other calves in the Burdizzo groups in the frequency of active behaviours, a threefold increase in time spent in abnormal postures and a cortisol response which was double the peak height of the Burdizzo group for most of the 180-minute observation period.
Results Behavioural changes
Significantly higher frequencies of restlessness, tail wagging, foot stamping and head turning were recorded for the rubber ring groups than for the handled, Burdizzo or surgical groups (Table 1). The only significant difference in these behaviours between the handled, Burdizzo or surgical groups was an increased tail wagging in the 21-day-old Burdizzo group. With regard to responses at different ages, the six-day-old calves showed significantly less tail wagging and foot stamping and more head turning than the calves in the older groups. The castrated calves, at each age, ate and sucked for less time than the control calves, the difference in total time spent eating being significant at 21 and 42 days old. Some eating by rubber ring castrated calves occurred in the first 12 minutes, that is, before the onset of abnormal behaviours. Normal lying (V 1 and V2) was significantly reduced after rubber ring castration compared with surgical and Burdizzo methods and handling (Tables 2 and 3), and it was replaced by more abnormal lying so that the differences in total lying between treatment groups were small. Most
TABLE 1 : Effects of age and method of castration on body movements (number), teat sucking and eating solids (minutes) during 180 minutes after treatment (means [SD]) Treatment
Age Restlessness (days) score
Control H Bu S aa
6 6 6 6
Control H Bu S RR Control H Bu S RR ANOVA SED F age F treat F inter
Tail wag
2 (1) D 3 (2) D 3 (1) D 15(11)
0 11 5 31
21 21 21 21
1 (0.4) 0 2 (2) D 4(2) D 18 (2)
1 (2) 0 1 (2) 0 40 (32) ad 11 (12~D 10 (16) D 0.5 (1) u 85 (46)x 83 (38)X
42 42 42 42
2 (1) d 2 (1)d 1 (1) D 9 (5) 2.7 2-2NS 26-8*** 1-4NS
(0) (13) (6) (33)
Foot stamp 0.5 (0.5) 5 (7) 2 (2) 20(22)
15 (8) 0 29 (20) d 45 (33) x 68 (48)
4 11 19 97
19'1 4'8* 9.2*** 1 '3NS
10'1 13"9"** 55.2*** 7-4***
Head turning 9 0,2 2 15
Sucking (1)
(5) D 8 (0.4) D 0 (4) 0 0 (16) 0.4
1(1) 2 (3) 2 (1) 9 (9)
(5) D 1 (2) (9) D 0-5 (0.5) (13) D 4 (5) (14) x 2 (3) x 4-2 1 "4NS 4.0* 1 '3NS
Eating Total (2) eating (1+2)
(10) 0 (0) (0) 0 (0) (0) 0.4 (0.8) (0.8) 0 (0)
8 0 0.4 0.4
(10) (0) (0.8) (0.8)
17(5) 2 (2) A 0 (0)A 2 (3)A
17(17) x 1 (2) ,~ 3 (3)A 0 (0)A
34(18) x 3 (5)'~ 4 (4)A 1 (2)A
11 (10) 3 (5) 1 (2) a 6 (10)
23(13) X 4 (5) ,~ 5 (5) A 4 (5) A
34(20) X 7 (7) ~ 6 (4) A 10 (15) A
4.0 1.7NS 10.4"** 0'8NS
4.9 6"8** 8.4*** 2.2
7.0 6"4** 14.4"** 1.7NS
H Handled, Bu Burdizzo, S Surgical, RR Rubber ring Superscripts show significant differences at P<0.01 (upper case) and P<0.05 (lower case) from H group (Aa), RR (gd) or six days (Xx) * P<0.05, ** P_<0.01, ***P<0.001 NS Not significant, SED Standard error of difference
11
Castration of calves TABLE 2: Effects of age and method of castration on the time (minutes) spent by calves in various lying and standing postures during 180 minutes after treatment (means [SD])
Treatment
Age (d~ays)
Control H Bu S RR Control H Bu S RR Control H Bu S RR
6 6 6 6 21 21 21 21 42 42 42 42
ANOVA SED F age F treat F inter
Recumbency Ventral V 1 +V2 V3
Lateral LL
Standing/walking
129 (31) 147 (15) d 128 (24) 96 (45) 96 (27) d 115 (26) D 104 (27)d 51 (24) X 88 (28) 101 (31) x 74 (38) 78 (25)
7 (11) 7 (10) 10 (16) 34 (33) 8 (17~d 3 (4) u 2 (3) D 43 (23) 6 (9) 6 (10) 25 (34) 24 (12)
2 (3) 1 (2) 5 (10) 2 (5)Y 0 (0) D 0 (0) D 0 (0) D 16 (26) 0 (0) 0 (0) 0 (0) 0 (0)y
21 '0 8.3*** 4"9* 0.7
13.8 0.02 5'4** 0.9
5"5 1-0 1-4 1.1
S1
S2
S3
44 (32) 13 (12) 24 (18) 20 (12) 76 (36) 30 (18) Ac 63 (24) 24 (8)'~c 86 (22) x 43 (20) A 45 (27) a 29 (12) A
0 (0) 0 (0) 12 (9) 0 (0) 14 (5) 0 (0) 27 (15) 0 (0)z 0 (0) 0 (0) 33 (12) A 0 (0) 12 (9)d 0 (0) 46 (21) A 1 (2)L 0 (0) 0 (0) D 31 (52) A 0 (0) D 36 (34) A 0.4 (1)D 43 (18) A 5 (7)
15'5 6.6** 10"0"** 0.9
14"4 2.0 7"5*** 0-7
1'5 2.2 3'0* 1.8
H Handled, Bu Burdizzo, S Surgical, RR Rubber ring Superscripts show significant differences at P_<0.01 (upper case), and P<_0.05 (lower case) from H group (Aa), S (c), RR (Dd) or six days (Xx), 21 days (Y) or 42 days (L) old * P_<0-05, ** P<0.01, *** P<0.001 SED Standard error of difference
TABLE 3: Effects of age and method of castration on total normal and abnormal postures occurring during the 180 minutes after treatment (means in minutes)
Treatment
Posture Total lying Normal lying Abnormal lying Abnormal standing Total abnormal V 1 to V3 + LL V 1 + V2 V3 + LL S2 + S3 V3 + LL + S2 + S3
Age at castration (days) (n=20) 6 142 21 109X 42 100X ANOVA SED 8"8 F age 12.1 *** Method of castration (n=15) Control - H 112 Bu 126 S 115 RR 115 ANOVA SED F treatment
10"2 0.8NS
125 91X 85 x
17 18 15
13 23 29 x
30 41 44
10'5 8.3"*
7'2 0-1NS
7"3 2.3NS
9'4 1.2NS
104 D 121 D 102 D 75
8D 5D 14D 39
0 25 A 21 ad 41A
8D 3lad 34 ad 80
12'1 4'9**
8-3 7'1 ***
8"4 8.1"**
10"9 15-8"**
Posture data from Table 2 summed and an ANOVAperformed with missing values H Handled, Bu Burdizzo, S Surgical, RR Rubber ring Superscripts show significant differences at P_<0.01 (upper case) and P<0.05 (lower case) from H group (Aa),RR (Dd) or six days (Xx) old ** P<0.01, *** P<0.001 NS Not significant, SED Standard error of difference
of the abnormal lying after all the forms of castration was in ventral (V3) rather than lateral posture (LL) (Table 2). LL was seen in only three calves after rubber ring castration and one calf, lying for 60 minutes, was responsible for the high mean LL in the 21-day-old group. The six-day-old calves
spent significantly more time lying than the older calves (Table 3). Compared with the handled group there was significantly more total abnormal standing after castration by each method, except in six-day-old calves and the surgical group at 21 days. Only four
12
1. S. Robertson, Y. E. Kent, V. Molony
calves (one surgical and three rubber ring) showed extreme abnormal standing postures ($3). The total time spent in abnormal postures by the rubber ring groups was significantly greater than for the other groups except the surgical group at 42 days (61 minutes) which also produced significantly (P<0.01) more of these postures than the handled group (six minutes).
and 60 minutes). Few of these activities were recorded after the first 30 minutes in the Burdizzo groups, while they were recorded for most of the three-hour period in the rubber ring groups. These activities in the surgical groups were less intense than in both the Burdizzo or the rubber groups. Tail wagging, however, was significantly (P<0.01) increased in the third hour after surgical castration in 42-day-old calves. Fig 2 shows the time courses of abnormal standing and abnormal lying after castration. Results for the castrated calves, supported by statistical analysis, were characterised as follows.
Changes in active behaviours and postures
In Fig 1 the frequency of restlessness (A, B, C), foot stamping (D, E, F) and tail wagging (G, H, I) illustrate the responses to surgical, Burdizzo and rubber ring castration and they can be related to the cortisol responses shown in Fig 3. In the Burdizzo group the change in these activities was immediate at all ages, reaching a peak in the first 12 minutes compared with the rubber ring group's greater and delayed response (peak between 30 BURDIZZO
Burdizzo. An immediate sharp rise in abnormal standing was sustained for 24 minutes in six-dayold calves but for longer periods in older calves; the peak occurring within the first 30 minutes. At all ages there were a few observations of abnormal standing between 120 and 180 minutes. There was
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FIG 1 : Frequency of restlessness (A, B, C), foot stamping (D, E, F) and tail wagging (G, H, I) in six minute periods after castration of calves of all ages (n=15)
Castration of calves minutes
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TIME AFTER CASTRATION (rain) FIG 2: Time spent (within six minute periods) in abnormal standing ~,,x:,ez,z-x,z-x,x~and abnormal lying ~ tion of calves aged six days (A, B, C), 21 days (D, E, F) and 42 days (G, H, I)
little abnormal lying observed, and that seen was mainly within the first 30 minutes except in 42day-old calves where the peak occurred between 60 and 90 minutes (not significant).
Surgical. As seen after Burdizzo castration there was an immediate sharp rise in abnormal standing sustained for 24 minutes in six- and 21-day-old calves. The response continued at a lower level for longer in the 42-day-old calves. There was little abnormal lying in the 21-day-old calves but at six and 42 days abnormal lying was observed from 30 to 180 minutes, peaking at 120 to 150 minutes in 42-day-old calves. Rubber ring. No abnormal behaviours were observed within the first 12 minutes, but after this there was a slow increase in the time spent in abnormal standing which peaked between 30 and 60 minutes in six- and 42-day-old calves and between 30 and 90 minutes in 21-day-old calves. Abnormal lying occurred later, predominantly
postures after castra-
between 90 and 180 minutes at all ages. The incidence of both postures was significantly greater than in handled, Burdizzo or surgical groups for at least 150 minutes.
Changes in PCC The changes in PCC after castration by Burdizzo, surgical and rubber ring methods in three ages of calves are compared to those in the control (handled) groups in Fig 3a, b and c. At each age the PfC of Burdizzo and surgical groups rose sharply after castration, peaking between 12 and 24 minutes. The surgical groups' peak values were significantly greater than those in the handled, Burdizzo and rubber ring groups, and those in the Burdizzo group were significantly greater than in the handled groups. However, after Burdizzo castration the PCC quickly returned to normal (within 72 minutes). Peak PCC after surgical methods was significantly greater in six- and 42-day-old calves than in 21-day-old calves (Fig
I. S. Robertson, J. E. Kent, V. Molony
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occurred at 12 minutes the main cortisol response at all ages occurred between 36 and 90 minutes. The peak of this response was later and lower than the main peaks after surgery and Burdizzo castration, but raised values were maintained for longer. For all methods, the PCC response to castration was lowest in 21-day-old calves. There were no age differences in the PCC response to handling in the control groups. Discussion
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FIG 4: Changes in plasma cortisol concentrations after surgical castration of calves at different ages. I I six days, A- - - -A 21 days, • . . . . • 42 days old. Superscripts show significant differences at P<0.01 (upper case) and P_<0.05 (lower case) from six days (X) or 21 days (YY)
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FIG 3: Change in plasma cortisol values in control (H) calves I I and after castration by surgery (S) • . . . . 0, Burdizzo (Bu) A- - - .4 and rubber ring (RR) • . . . . • at six days (a), 21 days (b) and 42 days (c) old. Superscripts show significant differences at P<0.01 (upper case) and P<_0-05 (lower case) from H group (Aa), Bu (Bb) or RR (Dd)
4) and the PCC was sustained at a high value for longer in 42-day-old calves. After rubber ring castration a small PCC peak similar to that in the handled calves occurred at 12 minutes. After rubber ring castration, although a small PCC peak similar to that in handled calves
Animals may either decrease or increase their activity in attempts to avoid or escape painful stimuli (Chapman et al 1985). Standing or lying still are appropriate responses to minimise stimulation of sensitised nociceptors, as found in damaged or inflamed tissues (Handwerker and Reeh 1991) and normally non-noxious stimuli, for example, walking, may be avoided after surgery or crushing injuries. The increased frequency of behaviours such as restlessness, tail wagging, foot stamping and kicking may be considered as attempts to escape from or remove the stimulus, for example, a biting insect causing pain. In rats (Grubb et al 1990) and lambs (D. F. Cottrell and V. Molony, unpublished observations) occlusion of the blood vessels to the testes does not immediately disable the afferent nerves or nociceptors and increased afferent activity may occur due to the sensitisation of nociceptors following hypoxia of tissues (Gebhart and Ness 1991, Handwerker and Reeh 1991). In contrast to the findings of Mellor et al
Castration of calves
(1991), rubber ring castration was followed by significant changes in behaviour when compared with both the control and the other castrated groups. The different results obtained in these two studies may be explained by differences in management and degrees of stress suffered by the calves before castration. Calves in the earlier work (Mellor et al 1991) were isolated from birth whereas the calves in these experiments were kept in pairs and when castrated by rubber ring techniques behaved similarly to both suckled calves with their dams (I. S. Robertson, unpublished observations) and to lambs with their dams (Molony et al 1993) castrated by the same method. Although restlessness occurred less frequently in calves than lambs (Molony et al 1993) after rubber ring castration it may also be a good indicator of pain in the calves after rubber ring castration since significant differences were obtained at each age between the rubber ring and other groups. Tail wagging and foot stamping occurred at high frequencies in the rubber ring groups and overall were at higher frequencies than after the other methods. Foot stamping, because it is more easily measured, may be a better indicator of pain than tail wagging. It was also recorded more fiequently in older calves after rubber ring and surgical castration, suggesting that pain suffered by older animals may be measured more readily than in the young using this parameter. After rubber ring castration there was a delay (10 to 15 minutes) before the onset of the active behaviours, abnormal postures and rise in plasma cortisol values, suggesting that the pain produced was the result of relatively slow pathophysiological changes produced by interruption of the blood supply rather than the immediate pressure exerted by the rubber ring. Abnormal standing and lying postures continued for longer than the one hour reported by Fenton et al (1958) and the abnormal standing was closely related in time to both peak Pcc and active behaviours. Whereas peak abnormal lying postures occurred after PeG abnormal standing and the active behaviours had almost returned to normal values, suggesting that abnormal standing postures rather than abnormal lying (Wood et al 1991) are more indicative of pain or discomfort after rubber ring castration in calves. Although there was some evidence from the behavioural observations that six-day-old calves
15
suffered less pain after rubber ring castration than older calves, it seems clear that they did suffer some pain for more than two hours. The successful application of the Burdizzo could, as well as destroying the blood supply to the testes, result in afferent activity from the testes being denied access to the central nervous system. However, crushing of nerves in scrotal tissues, spermatic cord and skin is likely to produce injury discharges (Wall at al 1974) and to release inflammatory mediators. In contrast to the delayed onset of abnormal behaviours and increased PCC after rubber ring castration, the increase in PCC, active behaviours and abnormal postures started immediately after Burdizzo application suggesting that pain from Burdizzo castration occurs mainly in response to the application of the Burdizzo provided that the afferent nerves from the testes and other distal tissues are destroyed. Pain, however, may occur later due to activity in intact afferent nerves from associated areas, for example, skin proximal to the line of crush. At each age the peak PCC was greater than after rubber ring castration but returned to normal more quickly, suggesting that the pain experienced may have been more intense but of shorter duration than after rubber ring castration. Detailed studies of the effects on afferent nervous activity after application of the Burdizzo are required to test this possibility further. Burdizzo castration produced a lower Pcc response than surgery, a result similar to that reported by Macaulay and Friend (1987a). Abnormal standing after castration by Burdizzo consisted mainly of 'statue' standing, a stationary posture possibly adopted to minimise pain. If the increase in abnormal standing, tail wagging and foot stamping seen in older calves indicates that they suffered pain, then this is evidence that the Burdizzo method used was better for younger calves. The method of surgical castration removes many of the nociceptors which contribute to the afferent input after castration by rubber ring. However, cutting tissues produces injury discharges in the remaining afferent nerves, releases inflammatory mediators and can cause haemorrhage. In this study haemorrhage was controlled by thermocautery. There was only a slight increase in active behaviours after surgery compared with rubber ring castration and the short period of abnormal standing, in agreement with Fell et al (1986), consisted mainly of 'statue' standing
16
L S. Robertson, J. E. Kent, V. Molony
rather than the agitation, swaying, walking backwards and easing of legs seen after rubber ring castration. Less time was spent performing abnormal behaviours after surgery which contrasts with the high plasma cortisol responses, making it difficult to decide whether surgery is more or less painful than rubber ring castration as previously discussed for castration and tail docking of lambs (Kent et al 1993, Molony et al 1993). Abnormal standing in six- and 21-day-old calves corresponded in time to the peak PCC and both parameters returned to control values more quickly than in 42-day-old calves, suggesting that the latter suffered more pain. Castrating older calves, Fell et al (1986), Macaulay and Friend (1987b) and Cohen et al (1990) all reported elevated cortisol values occurring for at least two hours. They also suggested, using PCC as the main index, that surgical castration was more stressful than either rubber ring, Burdizzo or chemical castration, respectively. This study has shown that, although there are some similarities in the responses of calves and lambs to castration, there are some notable differences including lower restlessness scores and lower plasma cortisol responses (Kent et al 1993). Abnormal standing and foot stamping appeared to be better indicators of pain from castration in calves than the abnormal lying and restlessness used for lambs (Wood et al 1991, Molony et al 1993). It is concluded that calves suffered pain after castration at each age and that six-day-old calves in reacting less violently and spending less time in abnormal postures probably suffered the least pain, while 42-day-old calves, which showed both a high incidence of abnormal postures and a raised PeG, particularly after surgical castration, may have suffered the most pain. All the methods of castration appeared to cause pain but lower behavioural and less sustained plasmal cortisol responses suggested that in general calves castrated successfully by Burdizzo probably suffered the least pain over the three-hour period studied. It is, however, difficult to decide whether an animal showing an apparent unwillingness to move accompanied by a high cortisol value after surgical castration might bein more or less pain than an animal that is showing active behaviours and a low cortisol value after rubber ring castration. To solve this problem it will be necessary to find ways of scaling the relative contributions of these different indices of pain.
Acknowledgements The authors wish to thank the Ministry of Agriculture, Fisheries and Food, the Moredun Research Institute and the Jean Sainsbury Trust for their support of this project. We are grateful for statistical advice given by Dr F. Wright of the Scottish Agricultural Statistics Services, Edinburgh.
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Castration o f calves WALL, P. S., WAXMAN, S. & BASBAUM. A. I. (1974) Ongoing activity in peripheral nerve: injury discharge. Experimental Neurology 45, 576-589 WOOD, G. N.. MOLONY, V., FLEETWOOD-WALKER, S. M. & MELLOR, D. J. (1991) Effect of local anaesthesia and intravenous naloxone on the changes in behaviour and plasma concentra-
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tions of cortisol produced by castration and tail docking with tight rubber rings in young lambs. Research in Veterinary Science 51, 193-199
Received October l, 1992 Accepted July 5, 1993