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Effect of dehorning on behaviour and plasma cortisol responses in young calves
APPLIED ANIMAL BEHAVIOUR SCIENCE
Applied Animal Behaviour Science 43 ( 1995) 239-247
Effect of dehorning on behaviour and plasma cortisol responses in young calves J.P. MO&se*, J.P. Cotte, D. Huonnic Centre Nutronal d’Etudes VPtPrinaires et Alirnentaires, BP 53 Beausernaine-22440,
Accepted 8 February
Ploufragan,
Frunce
1995
Abstract Behavioural and cortisol responses were investigated in respectively 84 and 80, 4-8 week old Montbeliard calves. The calves were dehorned either by applying a caustic preparation (potassium hydroxide) at 4 weeks or by heat cauterisation at 8 weeks. Behavioural studies, involving 84 calves in four treatments (with and without anaesthesia in dehorned by heat or chemical treatment), were performed by video monitoring or by visual observations. Throughout a 24 h period after disbudding, the ratio of lying to standing was unchanged in both treatments. The main behavioural modifications consisted of drastic but transient reduction in rubbing and social behaviours concomitant with an increase in behaviours indicative of distress or pain: restlessness (frequent standing up and lying down), repeated shaking of the head or ears and scratching the lesion with the hind foot. All behaviours indicative of pain or discomfort disappeared within 4 h in both treatments. Cortisol assays, performed on 80 calves (different from those used for behavioural studies) showed a peak in plasma cortisol levels ( 12-l 8 ng ml- ‘) but this was of moderate magnitude when compared with the 40 ng ml-’ shown by three animals in response to an intravenous injection of adrenocorticotropic hormone (ACTH). Behavioural changes and plasma cortisol data indicated that calves dehorned without anaesthesia experienced, in both treatments, intense but brief pain and discomfort. Although the comparison between treatments is questionable because of the differences in ages, animals disbudded by heat cauterisation tended to exhibit weaker reactions. Local anaesthesia reduced increases in plasma cortisol in chemically disbudded calves and induced a strong reduction of reactions in 60% of animals in both treatments. Those results suggest that further investigations are required to improve the reliability of a local anaesthetic under practical conditions.
Ke,vword.s: Calves;
* Corresponding
Dehorning; Behaviour; Cortisol
author
SSD10168-1591(95)00569-2
240
J.P. Morisse et al. /Applied Animal Behuviour Science 43 (1995) 239-247
1. Introduction
When beef type bulls are raised in group pens until 16-18 months of age, aggressive behaviours may result in injuries to stockmen and/or to animals themselves. To prevent accidents, the early removal of the horn producing area (disbudding) is routinely performed without anaesthesia, either by rubbing the bud area with a caustic preparation (Rosenberger, 1979) or by heat cauterisation. The second technique is performed when calves are 2 months old, the first has to be earlier (calves about 1 month old) to be efficient. The removal of the horn bud by heat cauterisation is allowed, without anaestbesia, in calves less than 4 weeks old, from the Draft Recommendations of the Standing Committee of the European Convention for the Protection of Farm Animals (Council of Europe 1988, T-Ap 88-7). From observations under practical conditions it is obvious that dehorning is painful, but little is known about the degree of pain and distress experienced by the calves. Although it cannot be considered as an indicator of pain, the adrenal cortex response is activated when animals are submitted to aversive or noxious stimuli (Selye, 1936; Mormtde et al., 1982). Changes in plasma levels have been used to evaluate the level of stress induced in calves by different castration techniques (Fell et al., 1986; Mellor and Murray, 1989), or in calves and lambs by different stressors (Stephens and Toner, 1975; Johnston and Buckland, 1976; Wood et al., 1991; Zavy et al., 1992). The present study used plasma cortisol levels and behavioural measures to try and evaluate the level of pain experienced by calves dehorned either by heat cauterisation or by chemical means with or without local anaesthesia.
2. Material and methods A total of 164 Montbeliard bull calves, 4-8 weeks of age, were used. The calves were kept at 3 weeks of age in pens, in groups of 5-12 animals. The bedding material in the pens was straw. The animals were fed a milk replacer twice daily during the first 10 days and then once a day until the weaning age (2 months). Concentrates (cereals and soja) and small amounts of maize silage were provided daily; hay and water were available ad libitum. Behavioural studies and cortisol monitoring were conducted separately using different groups, respectively of 84 and 80 calves, so as to avoid interferences between measures. 2.1. Dehorning procedures Disbudding was performed under routine conditions by the calves’ regular stockmen themselves; the two dehorning procedures were as follows. ( 1) Chemical treatment (CS) : each bud was rubbed for 2 min with a caustic preparation of potassium hydroxide using a caustic stick. The treatment was applied to calves at 4 weeks of age.
J.P. Morisse et al. /Applied Animal Behaviour Science 43 (1995) 239-247
241
(2) Heat cauterisation (HC) : an instrument electrically heated to 600°C was pressed firmly on each bud for about 1 min. The treatment was applied to calves at 8 weeks of age. 2.2. Local anaesthesia In each group (CS and HC), animals were divided into two groups: calves without anaesthesia (A - ) and calves injected subcutaneously 4 ml of Lignocaine (2%) 15 min before disbudding (A + ), on each side of the head, at the midpoint between the bud and the external end of the eye as described by Escard ( 1972) and Broutin ( 1980). 2.3. Behavioural
studies
Eighty-four calves were assigned to the various treatments as follows: 38 calves were disbudded using caustic sticks (CS), 19 without anaesthesia (CSA - ) and 19 with anaesthesia (CSA + ). Forty-six calves were disbudded by heat cauterisation (HC), 23 without anaesthesia (HCA - ) ,23 with anaesthesia (HCA + ) . From a preliminary study performed in two calf units, the main behaviours as described by Sato and Kuroda ( 1993) were selected and monitored as follows. Activity: Standing and lying times were recorded by video camera with infrared lighting during 96 sequences of 1 min every 15 min throughout the 24 h before and after disbudding. To accustom the animals to the camera system, the video apparatus was installed 2 days before the beginning of measurement. Single behavioural patterns were studied by visual observation over two 4 h corresponding periods on the days before and after disbudding. Three characteristic immediate reactions were recorded during disbudding: tail flapping, moving back, ventral falling. Their intensity was noted as low, medium or high. Vocalisations, expressed only during the treatment, were not taken into consideration as the calves could not vocalise freely because of the head restraint during dehorning. Other behaviours following disbudding were monitored: self grooming, rubbing (on pen sides or on the edges of feeders) and social behaviours (agonistic, sexual, head and body contacts, sucking, playing); standing up-lying down and behavioural activities in direct connection with the treatment, such as scratching the head with the hind foot or shaking the head, were also taken into consideration. 2.4. Plasma cortisol levels A preliminary study was conducted in three calves intravenously injected with 50 mg of exogenous adrenocorticotropic hormone ( ACTH; Synacthen@, Ciba Geigy Laboratories, Rueil Malmaison, France), at 12:00 h, in order to assess the reliability of the cortisol dosage by enzymo-immunoassay (EIA) ( Avrameas, 1968) in comparison with radioimmunoassay (RIA). Cortisol responses were investigated during the course of six dehorning sessions in 80 calves. The two dehorning treatments (CS and HC) were distributed over three experimental sites (stables of agricultural chambers in Brittany). The results are presented in Table 1.
242
J.P. Morisse et al. /Applied Animal Behaviour Science 43 (1995) 239-247
Table 1 Cortisol responses in 80 calves during the course of six dehorning sessions carried out at three different sites HC sites (n=48)
CS sites (n=32)
AA+
Controls Dehorned Controls Dehorned
1
2
4 4 4 4
4 4
3
1
2
3
4 4
4 4 4 4
4 4 4 4
4 4 4 4
In order to eliminate any distortion in cortisol secretion due to the circadian rhythm (Tun et al., 198 1) , dehorning was performed exactly at the same time ( 12:00 h) at each site and did not exceed 8 min for each group of four calves. Blood was collected individually from four animals in each pen, immediately before the disbudding and l-4 and 24 h after treatment; plasma cortisol was assayed by EIA using a commercial analysis kit (Merck Biotrol Laboratories, Nogent sur Maine, France). 2.5. Statistical analysis Results expressed in percentages were compared using the x2 test. Comparisons of plasma cortisol levels between the different treatments were performed using the non-parametric Mann-Whitney U-test.
3. Results 3.1. Behavioural studies
No difference was found in the ratio of standing to lying between two 24 h periods of observation (before and after disbudding) ; on average, calves spent about 67% of their time lying and 33% standing. Irrespective of treatment or anaesthesia, circadian activity was unchanged (Table 2). Table 2 Percentage of time. spent lying by calves dehorned chemically (CS) or by cauterisation (HC) with (A + ) and without (A - ) anaesthesia during the 24 h periods before ( - 24 h) and after ( + 24 h) treatment Treatment
A-
A+
-24h
+24h
-24h
+24h
(n=38)
67.2
68.6
67.0
71.0
HC (n=46)
67.3
66.0
68.9
71.2
cs
x2 test: non significant.
J.P. Morisse et al. /Applied Animal Behaviour Science 43 (1995) 239-247
Table 3 Intensity of immediate animals) Intensity
reactions
during dehorning
with (A + ) or without
Low
A(n=81) A+ (n=84)
243
(A - ) anaesthesia
(percentage
of
Medium
High
1.4
51.9
40.7
41.6
32.1
20.2
,y’ test: P< 0.001.
On average, the intensity of immediate reactions did not differ in unanaesthetised CS or HC disbudded animals but the administration of anaesthesia reduced the intensity of reactions (P < 0.001) in both treatments (Table 3). The effectiveness of anaesthesia was quite obvious in 60% of animals remaining motionless and showing no discernable evidence of pain or discomfort; the remaining 40% of calves attempted to avoid or escape the operation.
Table 4 Mean frequency of behaviour patterns in percentage of total observations in the two 4-h periods before ( - 4 h) and after ( + 4 h) chemical (CS) or heat cauterisation (HC) dehorning, with (A + ) or without (A - ) anaesthesia Treatment
Main behaviour
A-
A+
-4h
cs (n=38)
a
Self grooming Rubbing Social Lying downstanding up Scratching Head shaking
No. of observations x2 test HC (n=46)
b
No. of observations
x2 test “A-,n=19;A+,n=l9. bA-,n=23;A+,n=23.
+4h
+ 4h
-4h
57.6 3.4 12.4 14.4
13.9 1.2 0 38.5
59.9 4.0 5.3 19.0
18.9 0.7 0.2 30.9
1.7 10.5
17.5 28.8
1.3 10.5
19.3 30.0
1346
2150
1156
P
2752 P
64.5 6.5 15.0 9.0
23.9 0.5 0.2 15.2
12.7 5.5 5.1 11.5
30.3 2.4 3.2 19.3
0.5 4.5
18.4 41.8
0.5 4.1
21.3 23.4
3076
324-l P
3607
2834 P
244
J.P. Morisse et al. /Applied Animal Behaviour Science 43 (1995) 23%247
1
2
Time (ho”%)
1
4
2
Time (hd)
4
Fig. 1. Frequency of standing up and lying down during the first 4 h before (open bars) and after (solid bars) disbudding: CS, caustic stick; HC, heat cauterisation; A + , with anaesthesia; A -, without anaesthesia.
Concerning other behaviours, a marked evolution was observed within the 4 h period after disbudding (P < 0.001) in both treatments with or without anaesthesia (Table 4). Behavioural changes induced by disbudding were not significantly affected by anaesthesia but there was a trend towards less grooming and rubbing and more head shaking in HC anaesthetised calves. The short duration of reactions after disbudding such as lying down-standing up, is illustrated in Fig. 1 which shows that the number of movements was at a maximum l-2 h after treatment but returned to initial frequencies within 34 h. Table 5 Mean ( f SD) plasma cortisol levels (ng ml-‘) in treated (T) and control (C) animals with (A + ) or without (A - ) anaesthesia at 0, 1.4 and 24 h after disbudding Treatment
Caustic stick (n=32) CATACA+ TA+ Heat cauterisation (n=48) CATACA+ TA+
Time after disbudding (h) 0
1
4
8.4 f 6.4 13.2 f 8.2
3.9 f 7.0 18.1 &7.7 **
8.0 f 6.4 11.7*11.1
2.5f2.1 3.1*3.7
8.7 f 5.0 4.1 k3.8 *
3.8k3.0 14.6k9.6 **
2.5 f 2.3 5.0 f 3.0
3.6f4.9 2.9f2.4
3.2k4.1 6.3 f 3.7
3.7 f 2.9 12.2k5.0
5.0i5.2 2.9 f 2.7
2.3f 1.9 6.4 i-4.5 *
6.4 1t4.0 8.1 rt3.8
5.3 f 4.3 10.0 f 6.4
8.1 f6.3 9.7*7.1
6.1 f4.3 12.9*6.2 **
Mann-Whitney Utest: * P
24
J.P. Morisse et al. /Applied Animal Behaviour Science 43 (199.5) 239-247
245
3.2. Plasma cortisol levels In disbudded calves with or without anaesthesia, a rise in cortisol concentrations, significant in CS animals (P < 0.01) was observed 1 h after treatment, with a return to basal levels 4-24 h after disbudding (Table 5). In HC animals, the cortisol concentration observed in anaesthetised dehorned calves 24 h after disbudding remained significantly higher than in anaesthetisedcontrols (12.9 vs. 6.1 ng ml-‘) (PCO.01).
4. Discussion 4.1. Behavioural
studies
The similarity of the activity patterns during the 24 h periods before and after treatment (Table 2) should not be interpreted as a lack of reactions to dehorning. In fact, the global observation of the ratio of standing to lying is not a suitable measure of the intense but very brief changes induced by disbudding. The intensity of immediate reactions (Table 3) suggests the magnitude of the pain experienced by non-anaesthetised animals. When anaesthetised, calves displayed less intense reactions (P < 0.001) ; however, it must be emphasised that incomplete or partial effectiveness of anaesthesia was observed in 40% of animals; this may result either from poor handling of calves under field conditions or from individual differences in the neural topography of the horn area as described by Escard ( 1972) and Broutin ( 1980). It is obvious that dehorning induces strong modifications in behavioural patterns within the 4 h period after treatment and the absence of any significant effect of anaesthesia (despite small changes observed in some behaviours) (Table 4) was not unexpected, as the analgesic effect of lignocaine is of short duration. The evolution of some behaviours, such as lying down-standing up, with return to initial levels within 4 h, with or without anaesthesia, leads us to suggest that the pain or discomfort experienced by the calves is very brief. The comparison between the dehorning treatments is problematic, as these were carried out at different ages, according to routine procedures. 4.2. Plasma cortisol levels In the preliminary test performed on three calves, the plasma levels induced by ACTH reached 40 ng ml-’ at 30-60 min after infection and began to decrease 120-180 min after injection. These results, in agreement with those of other authors (Mormtde et al., 1982; Zavy et al., 1992)) show that cortisol levels after disbudding, during the same time period, are of moderate intensity. The increase in plasma cortisol levels 1 h after disbudding and their return to basal levels as soon as 4 h after treatment, suggests that behavioural activities and cortisol responses are synchronised in the expression of pain or discomfort. Concerning the choice of a dehorning procedure, chemical disbudding induced a higher cortisol response than heat cauterisation, leading to the conclusion that the former probably causes more distress.
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In calves dehorned by caustic treatment, the return to basal plasma cortisol levels is faster if local anaesthesia is performed, while in anaesthetised HC calves, cortisol levels remain high and even increase, suggesting that pain or discomfort rises as the analgesic effect declines. From the results it seems possible to conclude that dehorning is a painful operation but that its effects are very transitory, not exceeding 4 h. Although the two dehorning procedures are performed at different ages, which makes any comparison questionable, the lower cortisol rises observed after heat cauterisation suggest that HC could be less distressing, even though behavioural changes were not statistically different in both treatments. Local anaesthesia had no effect on behavioural changes observed during the first 4 hours after treatment but it clearly reduces the immediate reactions in both treatments. In fact, the use of anaesthesia led to the suppression of adverse reactions in 60% of calves but its effectiveness was partial or incomplete in 40% of animals. Further investigations are therefore required to improve the efficiency of local anaesthesia under field conditions.
Acknowledgements
The authors thank Professor F. Gamier from the National Veterinary School of Lyon for his help in RIA cortisol determinations, as well as the Responsibles of the experimental units of Agricultural Chambers in Brittany, who gave of their time, animals and facilities for this study. The authors are indebted to GIE Lait Viande de Bretagne for financial support.
References Avrameas, S.. 1968. Detection d’anticorps et d’antigenes a I’aide d’enzymes. Bull Sot. Chim. Biol., 50: 11691180. Broutin, M.O., 1980. Contribution a l’etude de l’dcomage des bovins. These Doct. Vet. Alfort no. 29, Fat. Med. Cr&eil, 47 pp. Council of Europe, 1988. Draft Recommendations of the Standing Committee of the European Convention for the Protection of Farm Animals. Council of Europe, 1988-TAP, 88-7. Escard, M., 1972. Contribution a l’bcomage des bovins par la scie dlectrique, These Doct Vet Alfort no. 22, Fat. Med. Cmteil, 38 pp. Fell, L.R., Wells, R. and Shutt, D.A., 1986. Stress in calves castrated surgically or by the application of rubber rings. Aust. Vet. J., 63: 16-18. Johnston, J.D. and Buckland, R.B., 1976. Response of male Holstein calves from seven sires to four management stresses as measured by plasma corticoid levels. Can. J. Anim. Sci., 56: 727-732. Mellor, D.J. and Murray, L., 1989. Effects of tail docking and castration on behaviour and plasma cortisol concentrations in young lambs. Res. Vet. Sci., 46: 387-391. Mormede, P., Bluthe, R.M. and Dantzer, R., 1982. Neuroendocrine strategies for assessing welfare: application to calf management systems. In: D. Smidt (Editor), Indicators Relevant to Farm Animal Welfare. Martinus Nijhoff, La Haye, pp. 3946. Rosenberger, G., 1979. Examen Clinique des Bovins, Point V&&inaire. Maisons-Alfort, Paris, 526 pp. Sato, S. and Ku&a, K., 1993. Behavioural characteristics of artificially reared calves. Anim. Sci. Technol., 64: 593-598. Selye, H., 1936. A syndrome produced by diverse nocuous agents. Nature, 138: 32-33. Stephens, D.B. and Toner, J.N., 1975. Husbandry influences on some physiological parameters of emotional responses in calves. Appl. Anim. Ethol., 1: 233-243.
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247
Tun, R., Eggenberger, E., Zerobin, K., Liischer, T. and Vetter, W., 1981. Twenty-four-hour secretory pattern of cortisol in the bull: Evidence of episodic secretion and circadian rhythm. Endocrinology, 109: 2208-2212. Wood, G.N., Molony, V. andFleetwood-Walker, S.M., 1991. Effectsof local anaesthesiaand intravenous naloxone on the changes in behaviour and plasma concentrations of cortisol produced by castration and tail docking with tight rubber rings in young lambs. Res. Vet. Sci., 51: 193-199. Zavy, M.T., Juniewicz, P.E., Phillips, W.A. and von Tungeln, D.L., 1992. Effect of initial restraint, weaning and transport stress on baseline and ACTH-stimulated cortisol responses in beef calves of different genotypes. Am. J. Vet. Res.. 53: 551-556.
Applied Animal Behaviour Science 43 ( 1995) 239-247
Effect of dehorning on behaviour and plasma cortisol responses in young calves J.P. MO&se*, J.P. Cotte, D. Huonnic Centre Nutronal d’Etudes VPtPrinaires et Alirnentaires, BP 53 Beausernaine-22440,
Accepted 8 February
Ploufragan,
Frunce
1995
Abstract Behavioural and cortisol responses were investigated in respectively 84 and 80, 4-8 week old Montbeliard calves. The calves were dehorned either by applying a caustic preparation (potassium hydroxide) at 4 weeks or by heat cauterisation at 8 weeks. Behavioural studies, involving 84 calves in four treatments (with and without anaesthesia in dehorned by heat or chemical treatment), were performed by video monitoring or by visual observations. Throughout a 24 h period after disbudding, the ratio of lying to standing was unchanged in both treatments. The main behavioural modifications consisted of drastic but transient reduction in rubbing and social behaviours concomitant with an increase in behaviours indicative of distress or pain: restlessness (frequent standing up and lying down), repeated shaking of the head or ears and scratching the lesion with the hind foot. All behaviours indicative of pain or discomfort disappeared within 4 h in both treatments. Cortisol assays, performed on 80 calves (different from those used for behavioural studies) showed a peak in plasma cortisol levels ( 12-l 8 ng ml- ‘) but this was of moderate magnitude when compared with the 40 ng ml-’ shown by three animals in response to an intravenous injection of adrenocorticotropic hormone (ACTH). Behavioural changes and plasma cortisol data indicated that calves dehorned without anaesthesia experienced, in both treatments, intense but brief pain and discomfort. Although the comparison between treatments is questionable because of the differences in ages, animals disbudded by heat cauterisation tended to exhibit weaker reactions. Local anaesthesia reduced increases in plasma cortisol in chemically disbudded calves and induced a strong reduction of reactions in 60% of animals in both treatments. Those results suggest that further investigations are required to improve the reliability of a local anaesthetic under practical conditions.
Ke,vword.s: Calves;
* Corresponding
Dehorning; Behaviour; Cortisol
author
SSD10168-1591(95)00569-2
240
J.P. Morisse et al. /Applied Animal Behuviour Science 43 (1995) 239-247
1. Introduction
When beef type bulls are raised in group pens until 16-18 months of age, aggressive behaviours may result in injuries to stockmen and/or to animals themselves. To prevent accidents, the early removal of the horn producing area (disbudding) is routinely performed without anaesthesia, either by rubbing the bud area with a caustic preparation (Rosenberger, 1979) or by heat cauterisation. The second technique is performed when calves are 2 months old, the first has to be earlier (calves about 1 month old) to be efficient. The removal of the horn bud by heat cauterisation is allowed, without anaestbesia, in calves less than 4 weeks old, from the Draft Recommendations of the Standing Committee of the European Convention for the Protection of Farm Animals (Council of Europe 1988, T-Ap 88-7). From observations under practical conditions it is obvious that dehorning is painful, but little is known about the degree of pain and distress experienced by the calves. Although it cannot be considered as an indicator of pain, the adrenal cortex response is activated when animals are submitted to aversive or noxious stimuli (Selye, 1936; Mormtde et al., 1982). Changes in plasma levels have been used to evaluate the level of stress induced in calves by different castration techniques (Fell et al., 1986; Mellor and Murray, 1989), or in calves and lambs by different stressors (Stephens and Toner, 1975; Johnston and Buckland, 1976; Wood et al., 1991; Zavy et al., 1992). The present study used plasma cortisol levels and behavioural measures to try and evaluate the level of pain experienced by calves dehorned either by heat cauterisation or by chemical means with or without local anaesthesia.
2. Material and methods A total of 164 Montbeliard bull calves, 4-8 weeks of age, were used. The calves were kept at 3 weeks of age in pens, in groups of 5-12 animals. The bedding material in the pens was straw. The animals were fed a milk replacer twice daily during the first 10 days and then once a day until the weaning age (2 months). Concentrates (cereals and soja) and small amounts of maize silage were provided daily; hay and water were available ad libitum. Behavioural studies and cortisol monitoring were conducted separately using different groups, respectively of 84 and 80 calves, so as to avoid interferences between measures. 2.1. Dehorning procedures Disbudding was performed under routine conditions by the calves’ regular stockmen themselves; the two dehorning procedures were as follows. ( 1) Chemical treatment (CS) : each bud was rubbed for 2 min with a caustic preparation of potassium hydroxide using a caustic stick. The treatment was applied to calves at 4 weeks of age.
J.P. Morisse et al. /Applied Animal Behaviour Science 43 (1995) 239-247
241
(2) Heat cauterisation (HC) : an instrument electrically heated to 600°C was pressed firmly on each bud for about 1 min. The treatment was applied to calves at 8 weeks of age. 2.2. Local anaesthesia In each group (CS and HC), animals were divided into two groups: calves without anaesthesia (A - ) and calves injected subcutaneously 4 ml of Lignocaine (2%) 15 min before disbudding (A + ), on each side of the head, at the midpoint between the bud and the external end of the eye as described by Escard ( 1972) and Broutin ( 1980). 2.3. Behavioural
studies
Eighty-four calves were assigned to the various treatments as follows: 38 calves were disbudded using caustic sticks (CS), 19 without anaesthesia (CSA - ) and 19 with anaesthesia (CSA + ). Forty-six calves were disbudded by heat cauterisation (HC), 23 without anaesthesia (HCA - ) ,23 with anaesthesia (HCA + ) . From a preliminary study performed in two calf units, the main behaviours as described by Sato and Kuroda ( 1993) were selected and monitored as follows. Activity: Standing and lying times were recorded by video camera with infrared lighting during 96 sequences of 1 min every 15 min throughout the 24 h before and after disbudding. To accustom the animals to the camera system, the video apparatus was installed 2 days before the beginning of measurement. Single behavioural patterns were studied by visual observation over two 4 h corresponding periods on the days before and after disbudding. Three characteristic immediate reactions were recorded during disbudding: tail flapping, moving back, ventral falling. Their intensity was noted as low, medium or high. Vocalisations, expressed only during the treatment, were not taken into consideration as the calves could not vocalise freely because of the head restraint during dehorning. Other behaviours following disbudding were monitored: self grooming, rubbing (on pen sides or on the edges of feeders) and social behaviours (agonistic, sexual, head and body contacts, sucking, playing); standing up-lying down and behavioural activities in direct connection with the treatment, such as scratching the head with the hind foot or shaking the head, were also taken into consideration. 2.4. Plasma cortisol levels A preliminary study was conducted in three calves intravenously injected with 50 mg of exogenous adrenocorticotropic hormone ( ACTH; Synacthen@, Ciba Geigy Laboratories, Rueil Malmaison, France), at 12:00 h, in order to assess the reliability of the cortisol dosage by enzymo-immunoassay (EIA) ( Avrameas, 1968) in comparison with radioimmunoassay (RIA). Cortisol responses were investigated during the course of six dehorning sessions in 80 calves. The two dehorning treatments (CS and HC) were distributed over three experimental sites (stables of agricultural chambers in Brittany). The results are presented in Table 1.
242
J.P. Morisse et al. /Applied Animal Behaviour Science 43 (1995) 239-247
Table 1 Cortisol responses in 80 calves during the course of six dehorning sessions carried out at three different sites HC sites (n=48)
CS sites (n=32)
AA+
Controls Dehorned Controls Dehorned
1
2
4 4 4 4
4 4
3
1
2
3
4 4
4 4 4 4
4 4 4 4
4 4 4 4
In order to eliminate any distortion in cortisol secretion due to the circadian rhythm (Tun et al., 198 1) , dehorning was performed exactly at the same time ( 12:00 h) at each site and did not exceed 8 min for each group of four calves. Blood was collected individually from four animals in each pen, immediately before the disbudding and l-4 and 24 h after treatment; plasma cortisol was assayed by EIA using a commercial analysis kit (Merck Biotrol Laboratories, Nogent sur Maine, France). 2.5. Statistical analysis Results expressed in percentages were compared using the x2 test. Comparisons of plasma cortisol levels between the different treatments were performed using the non-parametric Mann-Whitney U-test.
3. Results 3.1. Behavioural studies
No difference was found in the ratio of standing to lying between two 24 h periods of observation (before and after disbudding) ; on average, calves spent about 67% of their time lying and 33% standing. Irrespective of treatment or anaesthesia, circadian activity was unchanged (Table 2). Table 2 Percentage of time. spent lying by calves dehorned chemically (CS) or by cauterisation (HC) with (A + ) and without (A - ) anaesthesia during the 24 h periods before ( - 24 h) and after ( + 24 h) treatment Treatment
A-
A+
-24h
+24h
-24h
+24h
(n=38)
67.2
68.6
67.0
71.0
HC (n=46)
67.3
66.0
68.9
71.2
cs
x2 test: non significant.
J.P. Morisse et al. /Applied Animal Behaviour Science 43 (1995) 239-247
Table 3 Intensity of immediate animals) Intensity
reactions
during dehorning
with (A + ) or without
Low
A(n=81) A+ (n=84)
243
(A - ) anaesthesia
(percentage
of
Medium
High
1.4
51.9
40.7
41.6
32.1
20.2
,y’ test: P< 0.001.
On average, the intensity of immediate reactions did not differ in unanaesthetised CS or HC disbudded animals but the administration of anaesthesia reduced the intensity of reactions (P < 0.001) in both treatments (Table 3). The effectiveness of anaesthesia was quite obvious in 60% of animals remaining motionless and showing no discernable evidence of pain or discomfort; the remaining 40% of calves attempted to avoid or escape the operation.
Table 4 Mean frequency of behaviour patterns in percentage of total observations in the two 4-h periods before ( - 4 h) and after ( + 4 h) chemical (CS) or heat cauterisation (HC) dehorning, with (A + ) or without (A - ) anaesthesia Treatment
Main behaviour
A-
A+
-4h
cs (n=38)
a
Self grooming Rubbing Social Lying downstanding up Scratching Head shaking
No. of observations x2 test HC (n=46)
b
No. of observations
x2 test “A-,n=19;A+,n=l9. bA-,n=23;A+,n=23.
+4h
+ 4h
-4h
57.6 3.4 12.4 14.4
13.9 1.2 0 38.5
59.9 4.0 5.3 19.0
18.9 0.7 0.2 30.9
1.7 10.5
17.5 28.8
1.3 10.5
19.3 30.0
1346
2150
1156
P
2752 P
64.5 6.5 15.0 9.0
23.9 0.5 0.2 15.2
12.7 5.5 5.1 11.5
30.3 2.4 3.2 19.3
0.5 4.5
18.4 41.8
0.5 4.1
21.3 23.4
3076
324-l P
3607
2834 P
244
J.P. Morisse et al. /Applied Animal Behaviour Science 43 (1995) 23%247
1
2
Time (ho”%)
1
4
2
Time (hd)
4
Fig. 1. Frequency of standing up and lying down during the first 4 h before (open bars) and after (solid bars) disbudding: CS, caustic stick; HC, heat cauterisation; A + , with anaesthesia; A -, without anaesthesia.
Concerning other behaviours, a marked evolution was observed within the 4 h period after disbudding (P < 0.001) in both treatments with or without anaesthesia (Table 4). Behavioural changes induced by disbudding were not significantly affected by anaesthesia but there was a trend towards less grooming and rubbing and more head shaking in HC anaesthetised calves. The short duration of reactions after disbudding such as lying down-standing up, is illustrated in Fig. 1 which shows that the number of movements was at a maximum l-2 h after treatment but returned to initial frequencies within 34 h. Table 5 Mean ( f SD) plasma cortisol levels (ng ml-‘) in treated (T) and control (C) animals with (A + ) or without (A - ) anaesthesia at 0, 1.4 and 24 h after disbudding Treatment
Caustic stick (n=32) CATACA+ TA+ Heat cauterisation (n=48) CATACA+ TA+
Time after disbudding (h) 0
1
4
8.4 f 6.4 13.2 f 8.2
3.9 f 7.0 18.1 &7.7 **
8.0 f 6.4 11.7*11.1
2.5f2.1 3.1*3.7
8.7 f 5.0 4.1 k3.8 *
3.8k3.0 14.6k9.6 **
2.5 f 2.3 5.0 f 3.0
3.6f4.9 2.9f2.4
3.2k4.1 6.3 f 3.7
3.7 f 2.9 12.2k5.0
5.0i5.2 2.9 f 2.7
2.3f 1.9 6.4 i-4.5 *
6.4 1t4.0 8.1 rt3.8
5.3 f 4.3 10.0 f 6.4
8.1 f6.3 9.7*7.1
6.1 f4.3 12.9*6.2 **
Mann-Whitney Utest: * P
24
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245
3.2. Plasma cortisol levels In disbudded calves with or without anaesthesia, a rise in cortisol concentrations, significant in CS animals (P < 0.01) was observed 1 h after treatment, with a return to basal levels 4-24 h after disbudding (Table 5). In HC animals, the cortisol concentration observed in anaesthetised dehorned calves 24 h after disbudding remained significantly higher than in anaesthetisedcontrols (12.9 vs. 6.1 ng ml-‘) (PCO.01).
4. Discussion 4.1. Behavioural
studies
The similarity of the activity patterns during the 24 h periods before and after treatment (Table 2) should not be interpreted as a lack of reactions to dehorning. In fact, the global observation of the ratio of standing to lying is not a suitable measure of the intense but very brief changes induced by disbudding. The intensity of immediate reactions (Table 3) suggests the magnitude of the pain experienced by non-anaesthetised animals. When anaesthetised, calves displayed less intense reactions (P < 0.001) ; however, it must be emphasised that incomplete or partial effectiveness of anaesthesia was observed in 40% of animals; this may result either from poor handling of calves under field conditions or from individual differences in the neural topography of the horn area as described by Escard ( 1972) and Broutin ( 1980). It is obvious that dehorning induces strong modifications in behavioural patterns within the 4 h period after treatment and the absence of any significant effect of anaesthesia (despite small changes observed in some behaviours) (Table 4) was not unexpected, as the analgesic effect of lignocaine is of short duration. The evolution of some behaviours, such as lying down-standing up, with return to initial levels within 4 h, with or without anaesthesia, leads us to suggest that the pain or discomfort experienced by the calves is very brief. The comparison between the dehorning treatments is problematic, as these were carried out at different ages, according to routine procedures. 4.2. Plasma cortisol levels In the preliminary test performed on three calves, the plasma levels induced by ACTH reached 40 ng ml-’ at 30-60 min after infection and began to decrease 120-180 min after injection. These results, in agreement with those of other authors (Mormtde et al., 1982; Zavy et al., 1992)) show that cortisol levels after disbudding, during the same time period, are of moderate intensity. The increase in plasma cortisol levels 1 h after disbudding and their return to basal levels as soon as 4 h after treatment, suggests that behavioural activities and cortisol responses are synchronised in the expression of pain or discomfort. Concerning the choice of a dehorning procedure, chemical disbudding induced a higher cortisol response than heat cauterisation, leading to the conclusion that the former probably causes more distress.
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In calves dehorned by caustic treatment, the return to basal plasma cortisol levels is faster if local anaesthesia is performed, while in anaesthetised HC calves, cortisol levels remain high and even increase, suggesting that pain or discomfort rises as the analgesic effect declines. From the results it seems possible to conclude that dehorning is a painful operation but that its effects are very transitory, not exceeding 4 h. Although the two dehorning procedures are performed at different ages, which makes any comparison questionable, the lower cortisol rises observed after heat cauterisation suggest that HC could be less distressing, even though behavioural changes were not statistically different in both treatments. Local anaesthesia had no effect on behavioural changes observed during the first 4 hours after treatment but it clearly reduces the immediate reactions in both treatments. In fact, the use of anaesthesia led to the suppression of adverse reactions in 60% of calves but its effectiveness was partial or incomplete in 40% of animals. Further investigations are therefore required to improve the efficiency of local anaesthesia under field conditions.
Acknowledgements
The authors thank Professor F. Gamier from the National Veterinary School of Lyon for his help in RIA cortisol determinations, as well as the Responsibles of the experimental units of Agricultural Chambers in Brittany, who gave of their time, animals and facilities for this study. The authors are indebted to GIE Lait Viande de Bretagne for financial support.
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