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New Zealand Veterinary Journal
Review Article
Acute castration and/or tailing distress and its alleviation in lambs
D.J. Mellor *§ and K.J. Stafford †
Abstract
Purposes and approach: Acute castration and/or tailing distress in lambs has been examined extensively during the
last decade. At least 59 different approaches to assessing and alleviating this distress have been reported so that the
literature is quite complex. The purpose of this paper is to provide an overview of the literature on castration and/or
tailing distress, where the distress was assessed using acute changes in plasma cortisol concentrations. A method of
analysis involving the integrated cortisol response (i.e. the areas under the cortisol curves while the plasma concentration
is above pretreatment values) to each treatment and using treatments which were common to different studies as reference
points, allowed meaningful comparison within and between studies. A 6-point ranking scale emerged, where rank 1
represented the least distress and rank 6 the most distress.
Comparison of acute distress responses: This analysis revealed the following major points. Surgical methods of
castration and/or tailing cause the greatest cortisol responses (rank 5 or 6). Most ring and ring plus clamp methods of
castration plus tailing or castration, used without a local anaesthetic or systemic analgesic, cause rank 4 responses. One
form of ring plus clamp castration (i.e. applying the clamp for 10 s across the full width of the scrotum distal to the ring
in lambs aged no more than 1 week) reduces the cortisol response to rank 1. When these lambs are also tailed by applying
a ring and clamp in a similar manner to the tail, they also exhibit a rank 1 response. Local anaesthetic given 10-20 or 1-
2 min or 10-15 s before or immediately after ring only castration and/or tailing can virtually abolish the cortisol response
(rank 1), depending on the site(s) of injection. For ring or ring plus clamp castration, the most effective sites (as judged
by cortisol responses) are the neck of the scrotum or the testes. Delivery of local anaesthetic to achieve successful nerve
blockade can be by needle, high-pressure needleless administration or, for the tail only, by an aerosol spray. Local
anaesthetic injected into the scrotal neck, spermatic cords and/or testes has little effect on the overall cortisol response to
clamp castration. Reductions in cortisol responses to clamp castration or to ring tailing can occur after administration of
non-steroidal anti-inflammatory drugs. Most tailing methods elicit cortisol responses that are several ranks lower than
those caused by castration plus tailing or castration alone. Although tailing by most methods elicits rank 1 cortisol
responses, the use of local anaesthetic or non-steroidal anti-inflammatory drugs can reduce the response within the rank
1 range.
Recommendation: Farmers should be encouraged to choose the lowest ranked method that is economically and practically
feasible for them. Specific methods such as surgical castration should be discouraged.
(New Zealand Veterinary Journal 48, 33-43, 2000) Introduction
and Stafford, 1999a; Mellor et al., 2000). The responseto unpleasant experiences may be largely emotional (e.g.
During the last decade the pain-induced distress caused fear), largely physical (e.g. vigorous movement), or both by castration and tailing methods, and the different strat- (e.g. pain). The level of distress is assessed by variables egies for its alleviation, have been investigated extensively used to measure physiological stress and may be described in lambs (Tables I-III). The methods and circumstances as “minor”, “moderate”, “marked” and “extreme”. Al- have differed widely between studies, although, in some, though changes in these variables are objective measure- subtle but important aspects of methods and circum- ments, any conclusions about the subjective experiences stances have been explored. Consequently there is a need, that cause those changes remain judgements and not state- first, to compare the pain-induced distress caused by the ments of fact. That is because without sharing a common different methods of castration and/or tailing, second, to language an animal cannot tell us how painful or pleas- evaluate the efficacy of different ways of alleviating that distress and, third, to consider what practical advice can Two physiological systems are used to assess distress.
now be given to minimise animal welfare concerns.
These are the sympathetic adrenomedullary system whichis primarily concerned with fast-acting “fight-flight” re-sponses involving adrenaline, noradrenaline and heart Pain-induced distress and its
rate, and the hypothalamic-pituitary-adrenocortical assessment
(HPA) system which initiates longer lasting metabolic andanti-inflammatory responses that can promote healing.
It is necessary to clarify the meaning of the term “pain- Indices of HPA activity include plasma concentrations of induced distress” and how it can be assessed (see Mellor cortisol, adrenocorticotropic hormone (ACTH) and cor-ticotropin releasing factor (CRF). These hormones are * Animal Welfare Science and Bioethics Centre, Institute of Food, useful indices because HPA activity generally increases Nutrition and Human Health, Massey University, Palmerston North, in a graded way in response to the presumed noxiousness of different experiences. They do not measure pain, but † Animal Welfare Science and Bioethics Centre, Institute of Veterinary, provide an indication of how unpleasant the experience Animal and Biomedical Sciences, Massey University, PalmerstonNorth, New Zealand.
is emotionally and physically. The response time of the HPA axis makes it an insensitive index of the distress elic- New Zealand Veterinary Journal
ited in the first few minutes after an insult. Changes in Table I: Castration and tailing methods used in lambs and
calves. References refer to different combinations of castration
the sympathetic-adrenomedullary system may be more and tailing methods, or castration or tailing done separately by
different methods.
Behaviour is also a valuable index of distress because pain-related behaviours can be good indices of the dura- Castration
tion and the different phases of an experience. However,behavioural changes are often poorly correlated with the maximum intensity of the noxious experience as indicated by physiological variables (Mellor et al., 2000).
To date most assessments of castration and/or tailing with or without cautery.(5) (16) (17) (27) distress in lambs have been conducted using behaviourand plasma cortisol concentrations. The comparative Clamp (each spermatic cord).(1) (3) (17) (18) analysis provided here is based on the acute cortisol re- sponse. The strengths and weaknesses of this approach Normal ring.(1) (3) (5) (6) (9) (10) (12) (13) (14) (16) (17) (22) (25) (27) (28) have been explored in detail elsewhere (Stafford and Mellor, 1993; Mellor and Stafford, 1997; Mellor et al.,2000).
Each spermatic cord clamped.(1) (2) (3)Full-width of scrotum clamped.(1) (3) (5) (6) (16) (17) (18) (26) (27) Castration and tailing methods
Short scrotum (ring distal to testes).(1) (3) (9) (10) (19) Castration and tailing methods used in lambs and calvesare summarised in Table I.
In surgical castration the distal one third of the scrotum is cut off or incisions are made in each side of the scro- tum, to expose the testes. They are then removed by draw-ing them out without cutting the spermatic cords, or af- ter scraping and cutting, clamping or cauterising the sper-matic cords. The anatomy of the scrotum and testes is In clamp castration the spermatic cords are crushed through the scrotum. The usual method is to apply the Docking iron (severed by cautery) (4) (9) (10) (11) (23) (24) clamp to each cord once or twice while ensuring thatmedial scrotal tissues are uncrushed. Crushing the cords’ Ring (4) (7) (9) (10) (11) (12) (13) (14) (20) (21) (22) (23) (24) blood vessels prevents blood flow to the testes which at-rophy during the following 4 to 6 weeks.
Ring castration is done by applying a constrictive rubber ring to the neck of the scrotum with both testes distal to (1) Dinniss et al., (1997a), (2) Dinniss et al., (1997b), (3) Dinniss et al., (1999), (4) Graham et al., (1997), (5) Kent et al., (1993), (6) Kent et al., (1995), (7) Kent the ring. The ring obstructs blood flow through the testes et al., (1998), (8) Lester et al., (1991a), (9) Lester et al., (1991b), (10) Lester et and distal scrotal tissue, which atrophy and drop off after al., (1996), (11) Mazzaferro et al., (1993), (12) Mellor & Murray (1989a), (13) 4 to 6 weeks. Both “normal tension” and “tight rings” Mellor & Murray (1989b), (14) Mellor et al., (1991), (15) Mercy et al., (1985), (16) Molony et al., (1993), (17) Molony et al., (1995), (18) Molony et al., (1997), (19) In the short scrotum method a rubber ring is placed on Molony & Kent (1997), (20) Morris et al., (1994), (21) Rhodes et al., (1995), (22) the scrotum distal to the testes so that they are held against Shutt et al., (1988), (23) Stillwell et al., (1994), (24) St. Louis et al., (1994), (25) Sutherland et al., (1999), (26) Sutherland et al., (2000), (27) Thornton & Waterman-Pearson (1999), (28) Wood et al., (1991).
Genitofemoral nerve
the abdominal wall (Probert and Davies, 1986). The distal Superior spermatic nerve
scrotal tissue atrophies and drops off after 4 to 6 weeks.
Ring plus clamp castration involves placing a ring on the scrotal neck, proximal to the testes, immediately before Scrotal branch of the
or after applying a castration clamp once to each sper- pudenal nerve
matic cord leaving some scrotal tissue intact, or after ap- Distal cutaneous branch
plying it once across the full width of the scrotum. Clamp- of the sacral plexus
ing durations of 1, 5, 6 or 10 s have been used.
Chemical castration is done by injecting corrosive agents into the testes causing necrosis or sufficient impairment of testicular tissue to cause infertility. The agents usedinclude α-hydroxypropionic acid, lactic acid and formal- dehyde in ethanol (Mercy et al., 1985; Fordyce et al., 1989;Cohen et al., 1990).
Surgical tailing is done by cutting the tail off with a sharp Surgery plus clamp tailing involves cutting the tail off af- Figure 1: Anatomy of the scrotum and testes of lambs.
ter applying a castration clamp to the tail. The tail stump New Zealand Veterinary Journal
Figure 2: Examples of acute changes in the plasma cortisol concentrations: A, after surgical or ring castration plus
tailing and during control handling of lambs aged 4-6 weeks (redrawn from Lester et al., 1991a,b; reproduced with
permission of In Practice); B, after castration plus tailing of 1-week-old lambs using rings or rings plus clamp (10 s full
width), and during control handling (redrawn from Kent et al., 1995); and C, and D, after castration of lambs aged 4-8
weeks using a ring, ring plus clamp (10 s each cord), or ring 15-20 min after local anaesthetic injection into both spermatic
cords (Cd), the scrotal neck (Sc), the scrotal neck plus spermatic cords (Sc+Cd) or both testes (Te) (redrawn from
Dinniss et al., 1997a)
Strategies for alleviating acute
Tailing with a docking iron involves severing the tail by cautery using a heated chiselled metal device designed castration and tailing distress
for the purpose. An alternative less common method isto cut the tail off with a knife and immediately cauterise Castration and tailing methods which cause immediate and severe tissue damage (surgery, clamp, docking iron) Ring tailing is done by applying a rubber ring to the tail elicit a barrage of nerve impulses in pain pathways when to prevent blood flow through the distal tissues which the injury is inflicted and for a period thereafter, as indi- atrophy and drop off after 4 to 6 weeks.
cated by maximal rates of rise in plasma cortisol concen- Ring plus clamp tailing involves placing a ring on the tail trations (Figure 2). This initial barrage is usually followed and then clamping it with a castration clamp distal to the by “inflammatory pain” (Ren and Dubner, 1999). With other methods (ring, corrosive chemical) an initial nerve New Zealand Veterinary Journal
impulse barrage is followed by further tissue damage and distress is subsequently limited by the hypoxia/anoxia presumably impulse traffic which may take 30 minutes which disables the pain receptors in the tissues distal to or longer to cause maximum effects, as indicated by the ring. The same principles would apply to ring plus submaximal rates of increase in plasma cortisol concen- clamp and ring-only tailing methods. Severing the tail by trations (Figure 2). When the method used (e.g. surgery) cautery using a docking iron can also limit pain input does not obstruct impulse transmission from the area of from the tail stump possibly by destroying pain receptors damage, the inflammatory pain would be expected to in- in the burnt tissues (Lester et al., 1991b).
crease over a period of hours and then decline until thepain-producing features of inflammation resolve. On the Pharmacological alleviation
other hand, when the method used progressively impedes General anaesthesia renders an animal unconscious but pain impulse transmission, as occurs within about 1.5 is impractical for use with large numbers of farm animals hours of applying rubber rings for castration (Cottrell and (Table II). Local anaesthetic injections block impulse Molony, 1995), transmission of inflammatory nerve im- transmission in the treated nerves for the duration of ac- tion of the anaesthetic, which is usually about 2 hours forlignocaine (Dinniss et al., 1997a) and 3 hours or more Physical alleviation
for bupivacaine (Molony et al., 1997). The duration of Physical methods that obstruct transmission in pain nerve action is extended when rings obstruct blood flow and pathways or prevent blood flow and thus disable pain prevent clearance of the anaesthetic from tissues distal to receptors, have the potential to reduce castration and/or the rings. Injection sites for castration include the neck tailing distress. Thus, when a castration clamp damages and/or body of the scrotum, both spermatic cords or both the nerves in crushed tissues it interrupts nerve trans- testes, and for tailing the epidural space or subcutane- mission from tissues distal to each crush line. When each ously around the tail (Table II). Injections can be made cord is clamped separately and the impulse barrage that by needle, by a high-pressure needleless technique, or the accompanies clamp application has subsided, pain im- local anaesthetic can be sprayed on externally (Table II).
pulses from the testes and parts of the scrotum stop, but Local anaesthetic may be delivered 10-20 min before impulses in nerves in the uncrushed medial parts of the treatment, or more practically 1-2 min or 15-20 s before scrotum may continue. The full width crush approach, or 15-20 s after treatment (Table III).
applied to the scrotum during ring plus clamp castration, The analgesic non-steroidal anti-inflammatory drugs obstructs impulse transmission from both testes and all (NSAIDs), given intramuscularly or intravenously scrotal tissue distal to the crush. This approach can re- (Molony et al., 1997; McMeekan et al., 1998), have two duce the ischaemic pain which occurs with ring-only cas- advantages over local anaesthetics: their systemic distri- tration of young lambs. Ring-only castration causes is- bution allows actions on damaged tissues which are not chaemia which produces pain-induced distress, but the accessible to nerve blockade and their duration of action Table II: Pharmacological pain relieving strategies used for
Table III: Methods and timing of local anaesthetic administra-
castration and tailing. References refer to castration and tailing
tion for castration and tailing. References refer to castration
together or separately (see Table I footnote for number code).
and tailing together or separately (see Table I footnote for
number code).
Castration
Castration
10-20 min before treatment.(1) (3) (25) (28) Into neck of scrotum.(1) (3) (7) (19) (25) Into both testes.(1) (3) (7) (19) (25)Into scrotal neck + spermatic cords.(1) (3) Local anaesthetic given with a high pressure needleless device 10-20 min before treatment.(28)1-2 min before treatment.(4) Into the epidural space.(4) (20) (28)Subcutaneously around the tail.(4) (20) Local anaesthetic given with a high pressure needleless device Applied externally onto the skinaround the tail.(4) Local anaesthetic sprayApplied externally onto the skin New Zealand Veterinary Journal
is longer than for most local anaesthetics. However, Several other treatments, including ring castration at 1 NSAIDs do not significantly affect the pain impulse bar- or 4-6 weeks of age and ring plus clamp castration and rages associated with the initial tissue injury.
tailing at 3 or 6 weeks, also elicited 100% cortisol re-sponses, which allowed them to be used instead of ring Chronic consequences of
castration plus tailing for reference purposes when re-quired. The relative values of all the integrated cortisol castration/tailing
responses in each study were then calculated as the ratioof the response for each treatment against the response The long-term consequences of castration and/or tailing, for the reference group, expressed as a percentage.
which may include chronic pain, hyperalgesia, phantom Treatments that caused similar responses were assigned pain and neuropathic pain (Wood and Molony, 1992), the same rank and those causing different responses were assigned different ranks. The existence of similarities and Chronic pain is likely to be of low intensity with tailing differences was determined by reference to the signifi- because plasma cortisol concentrations remain low or at cance of between-treatment differences in the plasma control levels for at least 4 days afterwards (Stillwell et al., cortisol concentrations or the integrated responses, or 1994; Rhodes et al., 1995). However, changes in cortisol both, reported in the source papers. The ranks were iden- concentrations may not be a sensitive index of low-grade tified as: rank 1 = 1-30%, rank 2 = 30-55%, rank 3 = 70- pain, and behaviour might be better (Molony et al., 1995; 85%, rank 4 = 75-125% (includes the 100% reference Sutherland et al., 2000). If chronic pain occurs, it may arise groups), rank 5 = 165-170%, and rank 6 = 190-205%.
from slow resolution of inflammation in the damaged tis- By definition, therefore, the most benign treatments are sues, or from pathophysiological changes in pain thresh- in the low ranks and the most noxious are in the high olds or pain receptor input from healed tissues as occurs with hyperalgesia and phantom pain. The incidences of The percentages assigned to ranks 3 and 4 overlapped hyperalgesia and phantom pain are unknown in livestock because within-group variability differed between stud- but are well known in people (Bach et al., 1988; McQuay ies. In some studies the differences between the cortisol et al., 1988; Wall, 1988; Katz et al., 1992). Neuromas on responses to several treatments were not significant, cut nerves are a source of continuing impulse traffic in whereas in other studies similar differences between the pain pathways and may also be foci of persistent pain responses to other treatments did differ significantly. Rank (Blumberg and Janig, 1982; French and Morgan, 1992).
1 contains some cortisol responses that were significantly The long-term effects of castration and/or tailing on different, but they were assigned the same rank because production are usually insignificant, except for some re- duction in growth rate in castrates (Wohlt et al., 1982)due to the absence of testosterone (Probert and Davies, Evaluation of methods for castration
1986). The incidence of post-treatment systemic infec-tions is usually low, but local lesions, often accompanied plus tailing
by pus formation, are common for up to 6-8 weeks espe-cially with ring methods (Molony et al., 1995; Suther- Surgical castration plus tailing elicits the largest cortisol response and is therefore the most noxious method (rank6, Table IV; Figure 2A). Two approaches have been used.
Ranking acute cortisol responses to
The spermatic cords have been broken by tearing andthe tail simply cut off, or the cords and tail have been castration/tailing
clamped and cut with or without cautery (Table I). Un-fortunately the assessment of the latter treatment ended A system of analysis has been developed which allows before the acute cortisol response was complete (Kent et meaningful comparisons of the cortisol responses of lambs al., 1993), so the two approaches could not be compared in a range of studies where the breed and age and the here. Nevertheless, both surgical approaches cause sig- precise features of the cortisol assay methods differed.
nificantly larger cortisol responses than does ring castra- The analysis could only be applied when plasma cortisol concentrations were measured at sufficient frequency to Although ring castration plus tailing elicits an acute cor- define the cortisol response adequately.
tisol response which is approximately half that caused by The integrated cortisol responses to all treatments were surgery (Table IV; Figure 2A), the response is still sub- used to rank their relative noxiousness. The integrated stantial (rank 4). Likewise, short scrotum plus ring tail- cortisol response is the area between the plasma cortisol ing, and castration with a ring plus tailing with a docking concentration-time curve and a horizontal line drawn iron, also elicit rank 4 responses (Table IV). Therefore, through the pretreatment value while the concentrations less noxious alternatives have been sought. A small re- are above that value (Mellor and Murray, 1989b; Lester duction in the response is achieved by using tighter than et. al., 1991b). Most reports present the transient increases normal rubber rings (rank 3). However, the most benign in plasma cortisol concentrations that followed castra- castration and tailing method (rank 1) produces an acute tion and/or tailing graphically (Figure 2), and sometimes cortisol response equivalent to that seen in control lambs they also quote the associated integrated cortisol re- which are familiar with handling. It involves injecting lo- sponses. For those studies where the integrated responses cal anaesthetic into the scrotal neck, both spermatic cords, were not reported, the responses were calculated from both testes and the epidural space 15-20 min before ring the cortisol concentration-time graph.
castration and tailing (Table IV). Despite its effective- The integrated response for castration plus tailing with ness in virtually abolishing the cortisol response this rings was taken as the reference point because it was com- method is impractical for general farm use. A more prac- mon to most studies. It was assigned a value of 100%.
tical alternative of injecting local anaesthetic into the scro- New Zealand Veterinary Journal
tal neck 15-20 s before applying rings to the scrotum and (rank 6; Table V). Clamp castration (10 s on each sper- tail, is not as effective but does reduce the cortisol re- matic cord) causes a rank 5 response at 4-8 weeks and a sponse to rank 2. In contrast, injecting local anaesthetic rank 4 response at 3 weeks of age (Table V). The differ- into both testes 10-15 s after ring application to the scro- ence between these responses, which were quantified in tum and tail confers no significant benefit (rank 4).
separate studies (Dinniss et al., 1997a; Molony et al., The combined ring plus clamp method of castration plus 1997), could be due to the effects of postnatal age, breed tailing is among the least noxious (rank 1), but only in 1- of sheep or to the use of different clamps or clamping week-old lambs and when the castration clamp is applied for 10 s across the full width of the scrotum and tail distal Ring castration elicits rank 4 cortisol responses in lambs to the rings (Table IV; Figure 2B). Applying a clamp in a aged between 1 and 8 weeks (Table V). Short scrotum similar manner for 6 s after ring placement effects a smaller creation reduces the cortisol response to rank 3 (Table reduction in the cortisol response at 1 week of age (rank V). However, no significant reduction in the response 3), and has little or no effect at 3 or 6 weeks (rank 4).
occurs when ring castration is combined with full width Other variants of the ring plus clamp method confer no scrotal clamping for 10 s at 3 weeks (Table V), or with significant benefit between 3 and 8 weeks.
clamping each spermatic cord separately for 1, 5 or 10 s Using a castration clamp for castration plus tailing (10 s at 4-8 weeks of age (Table V; Figure 2C).
on each spermatic cord and 3 s on the tail) in 1-week-old Injecting local anaesthetic into both spermatic cords or lambs elicits a rank 4 cortisol response, like ring castra- into the scrotal neck 15-20 or 1-2 min before clamp cas- tration (10 s each cord) does not reduce the cortisol re-sponse below rank 4, nor does injecting it into both testes Evaluation of castration methods
1-2 min before ring plus clamp castration (10 s full width)(Table V).
Of all the castration methods assessed, surgical castra- Some local anaesthetic strategies can markedly tion at 4-5 weeks of age elicits the largest cortisol response reduce the cortisol responses to several castration meth- Table IV: Ranking of the overall levels of acute pain-induced distress, as judged by cortisol responses, caused by different methods of
castration plus tailing with and without local anaesthetic in lambs.
Rank - (Cortisol Response1)
Castration plus tailing method
6 (190-205%)
5 (165-170%)
4 (75-125%)
CT ring, 1-8 weeks (standard response: 100%)1SS ring T ring, 4-5 weeksC ring T iron, 4-5 weeks C ring + clamp (6 s each cord) T ring, 6-8 weeksC ring + clamp (6 s each cord) T ring + clamp (6 s), 6-8 weeks C ring + clamp (6 s full width) T ring + clamp (6 s), 3 weeksC ring + clamp (6 s full width) T ring + clamp (6 s), 6 weeksC ring + clamp (6 s full width) T ring + clamp (6 s), 3-6 weeksC ring + clamp (6 s full width) T ring, 3-6 weeksC ring + clamp (10 s full width) T ring, 3-6 weeks C clamp (10 s each cord) T clamp (3 s), 1 week 3 (70-85%)
C ring + clamp (6 s full width) T ring + clamp (6 s), 1 week 2 (30-55%)
1 (1-30%)
C ring + clamp (10 s full width) T ring + clamp (10 s), 1 week LA Cd Sc Te Epi (15-20 min before) CT ring, 1 week Control handling, first weekLA control (15-20 min before), 1-8 weeksLA control (10-15 s before/after), 3-6 weeks Integrated (overall) cortisol response as a percentage of that caused by CT ring, expressed to the nearest 5%.
Data obtained only during the first 4 h after treatment (Lester et al., 1991a) were corrected by assuming that 72% of the complete response occurred before and 28% C =castration; T = tailing; SS = short scrotum. LA= local anaesthetic; Cd = spermatic cords; Epi = epidural; Sc = scrotal neck; Ta = tail; Te = testes.
New Zealand Veterinary Journal
ods that elicit rank 4 responses (Table V; Figure 2D).
1997a), and the high-pressure needleless administration Thus, ring castration elicits rank 1 cortisol responses during transit of the anaesthetic bolus from the wall of when local anaesthetic is administered as follows: by nee- the scrotum to the testes. Local anaesthetic placed in the dle into the scrotal neck plus spermatic cords, into the vaginal cavity at least partially anaesthetises the scrotum scrotal neck or into the testes 15-20 min before treat- and the testes. The cortisol responses suggest that these ment; by a needleless high-pressure device into the delivery methods achieve complete or almost complete testes 5-10 s before ring application; or by needle into anaesthesia from about 10 minutes after castration. How- the scrotal neck 5-10 s after ring application. Likewise, ever, some distress may occur earlier, when the local an- injecting local anaesthetic into the scrotal neck 15-20 min aesthetic has had little time to act, but that would not be before ring plus clamp castration (10 s each cord) detected by the cortisol response because of the slower reduces the cortisol response to rank 1 (Table V). These response time of the hypothalamic-pituitary-adrenocor- delivery methods usually place local anaesthetic into tical axis compared to the sympathetic adrenomedullary the vaginal cavity of the scrotum (Figure 1). The scrotal neck injections achieve that directly, the testicular injec- Some other local anaesthetic strategies are less effective tions by leakage after needle withdrawal (Dinniss et al., but do confer some benefit. These include injecting local Table V: Ranking of the overall levels of acute pain-induced distress, as judged by cortisol responses, caused by different methods of
castration with and without local anaesthetic or a non-steroidal anti-inflammatory drug in lambs.
Rank - (Cortisol Response1)
Castration method
6 (190-205%)
5 (165-170%)
4 (75-125%)
Ring, 1-8 weeks (standard response: 100%)1 Ring + clamp (10 s each cord), 4-8 weeksRing + clamp (5 s each cord), 4-8 weeksRing + clamp (1 s each cord), 4-8 weeksRing + clamp (10 s full width), 3 weeks LA Sc (15-20 min before) clamp (10 s each cord), 4-8 weeksLA Cd (15-20 min before) clamp (10 s each cord), 4-8 weeksLA Te (1-2 min before) clamp (10 s each cord), 3 weeksLA Te (1-2 min before) ring + clamp (10 s full width), 3 weeks 3 (70-85%)
LA Cd (15-20 min before) ring, 4-8 weeksLA Cd (15-20 min before) ring + clamp (10 s each cord), 4-8 weeks 2 (30-55%)
NSAID (20 min before) clamp (10 s each cord), 3 weeks 1 (1-30%)
LA Cd Sc (15-20 min before) ring, 4-8 weeksLA Sc (15-20 min before) ring, 4-8 weeksLA Te (15-20 min before) ring, 4-8 weeksLA Sc (15-20 min before) ring + clamp (10 s each cord), 4-8 weeks LA Ne-Te3 (5-10 s before) ring, 1 weekLA Sc (5-10 s after) ring, 1 weekLA Sc (5-10 s after) ring + clamp (10 s full width), 1 week Control handling, first weekLA control (15-20 min before), 1-8 weeksLA control (10-15 s before/after), 3-6 weeks Integrated cortisol response as a percentage of that caused by CT ring, expressed to the nearest 5%.
Data obtained only during the first 4 h after treatment (Lester et al., 1991a) were corrected by assuming that, as for CT surgery, 72% of the complete response occurred before and 28% after 4 h (Lester et al., 1991b).
Needleless injection into the testes through the scrotum would also anaesthetise the scrotum.
Ne = needleless injection; LA= local anaesthetic; Cd = spermatic cords; Sc = scrotal neck; Te = testes; NSAID = non-steroidal anti-inflammatory drug.
New Zealand Veterinary Journal
anaesthetic into the spermatic cords 15-20 min before 8 weeks of age (rank 2) are usually greater than those ring castration, or ring plus clamp castration (10 s each elicited during the first week (rank 1). This is probably cord), which reduces the cortisol response to rank 3 in due to older paddock-reared lambs being far less used to both cases (Table V). Likewise, high-pressure needleless handling than are younger lambs born and reared indoors administration of local anaesthetic into the scrotal neck (Mellor and Murray, 1989a; Lester et al., 1991b). Like (affecting nerves in the scrotum, vaginal cavity and sper- control handling, tailing with a ring or a docking iron matic cords) 5-10 s after ring castration, reduces the usual elicits rank 2 responses at 4-5 weeks of age, but this does rank 4 response to rank 2 (Table V).
not mean that tailing by these methods is pain free. It is Ring plus clamp castration (10 s full width) of 1-week- more likely to be simply fortuitous that the pain-induced old lambs elicits a rank 1 response, a marked improve- distress caused by these tailing methods and the predomi- ment on the response to ring only castration (rank 4).
nantly emotional distress of unfamiliar control handling With this same method, injecting local anaesthetic into elicit similar cortisol responses at this age (Lester et al., the scrotal neck 5-10 s after ring placement and clamp- 1991b). In younger lambs tailing with rings causes greater ing further reduces the response within rank 1 (Table V).
cortisol responses than does familiar control handling Finally, cortisol responses to clamp castration can be (Mellor and Murray, 1989a; Graham et al., 1997; Kent et reduced. At 4-8 weeks of age, applying the clamp to each al., 1998), but both are in rank 1 (Table VI). Moreover, spermatic cord for 1 s as opposed to 10 s reduces the various modifications to the ring tailing method at 1 or 3 cortisol response from rank 5 to rank 3, and at 3 weeks, weeks of age can reduce the cortisol responses even within injecting the NSAID, diclofenac intramuscularly, 20 min rank 1 (Table VI). Thus, injecting diclofenac before clamp castration (10 s each cord) reduces the re- intramuscularly 20 min before ring application, or inject- sponse from rank 4 to rank 2 (Table V).
ing local anaesthetic into the epidural space or subcuta-neously around the tail 1-2 min before or spraying it onto Evaluation of tailing methods
the tail 5-15 s before ring application, or injecting it byneedle or by the high-pressure needleless approach 5-10 Surgical tailing causes the largest cortisol response (rank s after ring application, all elicit lower cortisol responses 5), but the responses to all other tailing methods are than does ring tailing alone (Graham et al., 1997; Kent et ranked 1 or 2 (Table VI). In order to interpret the re- al., 1998). In addition, lower responses are also elicited sponses of lambs to the non-surgical methods, it is first by the docking iron and the ring plus clamp (10 s) meth- necessary to note that responses to control handling at 4- ods of tailing (Mazzaferro et al., 1993; Stillwell et al., 1994; Table VI: Ranking of the overall levels of acute pain-induced distress, as judged by cortisol responses, caused by different methods of
tailing with and without local anaesthetic or a non-steroidal anti-inflammatory drug in lambs.
Rank - (Cortisol Response1)
Tailing method
5 (165-170%)
2 (30-55%)
1 (1-30%)
Ring + clamp (10 s), 3 weeksRing + clamp (10 s), 1 week LA Ta (1-2 min before) ring, 3 weeksLA Epi (1-2 min before) ring, 3 weeksLA Spray (5-15 s before) ring, 3 weeks LA Ta (5-10 s after) ring, 1 weekLA Ne-Ta (5-10 s after) ring, 1 weekLA Ne-Ta (5-10 s after) ring + clamp (10 s), 1 week Control handling, first weekLA control (15-20 min before), 1-8 weeksLA control (10-15 s before/after), 3-6 weeks Integrated cortisol response as a percentage of that caused by CT ring, expressed to the nearest 5%.
Data obtained only during the first 4 h after treatment (Lester et al., 1991a) were corrected by assuming that, as for CT surgery, 72% of the complete response occurred before and 28% after 4 h (Lester et al., 1991b).
Epi = epidural; LA= local anaesthetic; Ne = needleless injection; NSAID = non-steroidal anti-inflammatory drug; Spray = externally applied; Ta = subcutaneously into the New Zealand Veterinary Journal
Kent et al., 1998), but high-pressure needleless adminis- spraying the local anaesthetic together with an evaporative tration of local anaesthetic into the tail 5-10 s after ring coolant onto the tail where the ring is to be applied is also plus clamp (10 s) tailing does not further reduce the re- effective, but the need to shear the area first is an impedi- Once cortisol concentrations return to control values at 2-3 hours after ring tailing, they apparently remain there until at least 24 hours after treatment (Rhodes et al., 1994, Local anaesthetic is much less effective in reducing the 1995), and for a further 3 days (Stillwell et al., 1994).
cortisol response to clamp than to ring castration (Dinnisset al., 1997a; Molony et al., 1997).
Evaluation of particular features of
Non-steroidal anti-inflammatory drugs (NSAIDs)
some methods
Prior intramuscular injection of an NSAID reduces thecortisol response to clamp castration (10 s each cord) Tightness of rings
and to ring tailing (Molony et al., 1997; Graham et al., Rings that are tighter than the normal rings might dis- 1997). Although some NSAIDs have central analgesic able nerve impulse transmission from the distal tissues effects (McCormack and Brune, 1991; Dart, 1992; earlier, thereby accounting for the reduction in the corti- Urquhart, 1993), their main action is on inflammation- sol response to ring castration plus tailing from rank 4 to related pain, so that little or no alleviation of the pain rank 3 when tight rings are used (Kent et al., 1995). As caused by clamping itself and possibly by ring applica- the duration of response is reduced, but not the magni- tion can be expected. The cortisol response appears to tude, the question of whether the duration or the magni- reflect this. It is not known whether or not the 20 min tude of the response is more important from the animal’s interval between injection and treatment is necessary for maximum beneficial effects, but if it is, this delay wouldconstitute a significant practical impediment to use of Clamping with rings
The most effective way to minimise the distress caused NSAID use with surgical castration should be investi- to 1 week old lambs by ring castration plus tailing with- gated as it may deal more effectively with areas of tissue out local anaesthetic, is to use the combined ring plus damage that are inaccessible to uncomplicated nerve clamp (full width) method on the scrotum and tail, with blockade techniques. The benefits of using an NSAID the clamp applied for 10 s. In older lambs this approach together with local anaesthesia would also be worth ex- is not as effective. The age limit for its effective use, the ploring. Such approaches could reduce castration distress cost of the clamp, the skill required to use it, and the when it is necessary to use surgical as opposed to other flinching of the lambs each time the clamp is applied, may be impediments to acceptance of this method byfarmers.
Use of distress ranking to improve
Use of local anaesthetic
animal welfare
Ring methodsThe efficacy of local anaesthetic in reducing the cortisol Having ranked the available methods, the next issue to distress responses to ring castration plus tailing or ring be addressed is how that information should be used to castration depends on the timing, the sites and the mode improve animal welfare. As noted elsewhere (Mellor and Stafford, 1999b), two approaches suggest themselves – Although it may be desirable to wait 10-20 min between the “gold standard” approach and the “incremental im- injection and ring application to maximise efficacy, ma- provement” approach. The “gold standard” is not to cas- jor reductions in the cortisol distress responses can be trate or tail any animal. However, when it is necessary achieved with intervals of 1-2 min, and even as short as the next best “gold standard” is to select rank 1 proce- 10-15 s. Moreover, injecting lambs immediately after ring dures and ban all others. Alternatively, adopting “incre- application can also be very effective.
mental improvement”, we can draw attention to the rank- It is not necessary to inject all major sites (scrotal neck, ing of the different procedures and recommend the use testes and spermatic cords) to achieve effective local an- of the lowest ranked procedure that is practically feasible aesthesia for castration. The most effective injection sites in each particular circumstance. Also consistent with “in- are apparently the neck of the scrotum or both testes. It cremental improvement” is very strongly discouraging the is important for the anaesthetic to be deposited in the most noxious procedures, provided that more benign and vaginal cavity of the scrotum. Injection of local anaes- practical alternatives are readily available.
thetic into the spermatic cords only is less effective than Imposing bans based on a “gold standard” has three main disadvantages. First, further study of acute distress Injecting the tail subcutaneously at the site of ring ap- responses may reveal a need to revise the ranking, thereby plication requires less skill than epidural injections and calling into question the wisdom of the original ban and both are effective in reducing the cortisol distress response reducing the credibility of subsequent bans. It is com- mon in science to revise initial interpretations as further High-pressure needleless administration is apparently work is completed. The area of distress assessment is no as effective as conventional needle delivery of local an- exception, as an account of the chronological develop- aesthetic in reducing the cortisol distress response to ring ment of ideas about castration and tailing distress would castration and to ring only or ring plus clamp tailing.
reveal. Moreover, little is known about chronic pain However, the cost of the high-pressure equipment and (Thornton and Waterman-Pearson, 1999) and, if it oc- the skill required to use it are disadvantages. For tailing, curs, about what association it has with wound healing New Zealand Veterinary Journal
after castration and/or tailing by different methods Cohen RDH, King BD, Thomas LR, Janzen ED. Efficacy and stress of (Molony et al., 1995; Sutherland et al., 2000). Second, chemical versus surgical castration of cattle. Canadian Journal ofAnimal Science 70, 1063-1072, 1990.
an inflexible ban may alienate those who want to make Cottrell DF, Molony V. Afferent activity in the superior spermatic nerve improvements but cannot meet the new higher standard.
of lambs - the effects of application of rubber castration rings. Vet- Third, a ban becomes discredited if it is ignored and can- erinary Research Communications 19, 503-515, 1995.
Dart CM. The basis for the use of steroids/non-steroidal anti-inflam- The alternative “incremental improvement” approach matory drugs (NSAID) for pain control in clinical practice. In:Animal Pain and its Control, Proceedings 226, 351-366. Postgradu- is preferred because it is likely to recruit more farmers ate Committee in Veterinary Science, University of Sydney, NSW, into making some welfare improvement. For those who cannot meet the highest standard immediately, their small Dinniss AS, Mellor DJ, Stafford KJ, Bruce RA, Ward RN. Acute corti- changes for the better are recognised as a good start, they sol responses of lambs to castration using a rubber ring and/or acastrating clamp with or without local anaesthetic. New Zealand feel positive about them, and that makes them more open Veterinary Journal 45, 114-121, 1997a.
to make other improvements in the future as their own Dinniss AS, Stafford KJ, Mellor DJ, Bruce RA, Ward RN. Acute corti- circumstances change and as consumers demand higher sol responses of lambs castrated and tailed using rubber rings with welfare standards. The emphasis is on farmers making or without a castrating clamp. Australian Veterinary Journal 75, the greatest improvement that is economically and prac- Dinniss AS, Stafford KJ, Mellor DJ, Bruce RA, Ward RN. The behav- tically feasible for them in their particular circumstances.
iour pattern of lambs after castration using a rubber ring and/or In light of this, the present analysis does give several castrating clamp with or without local anaesthetic. New Zealand direct pointers on how castration and/or tailing of lambs Veterinary Journal 47, 198-203, 1999.
should be carried out. It is usually not practical for farm- Fordyce G, Hodge PB, Beaman NJ, Laing AR, Campero C, Shepherd RK. An evaluation of calf castration by intratesticular injection of ers in New Zealand to castrate and tail lambs under 1 a lactic acid solution. Australian Veterinary Journal 66, 272-276, week of age and encouraging early castration and tailing may interfere with ewe-lamb bonding. Moreover, castra- French NP, Morgan KL. Neuromata in docked lambs’ tails. Research tion is rarely carried out on male lambs without tailing.
in Veterinary Science 52, 389-390, 1992.
Therefore recommendations for New Zealand need to Graham MJ, Kent JE, Molony V. Effects of four analgesic treatments on the behavioural and cortisol responses of 3-week-old lambs to be directed towards older lambs and towards castration tail docking. The Veterinary Journal 153, 87-97, 1997.
Katz J, Kavanagh BP, Sandler AN, Nierenberg H, Boylan JF, Friedlander Wherever lamb management permits, castration should M, Shaw BF. Preemptive analgesia: clinical evidence of be avoided. Castration plus tailing by surgery (knife) or neuroplasticity contributing to postoperative pain. Anesthesiology77, 439-446, 1992.
clamp should be phased out as should tailing by surgery.
Kent JE, Molony V, Graham MJ. Comparison of methods for the re- Of the alternative castration methods, short-scrotum duction of acute pain produced by rubber ring castration or tail should be preferred to the ring method if management docking of week-old lambs. The Veterinary Journal 155, 39-51, permits. The widespread use of local anaesthesia or sys- temic analgesia is not likely to be acceptable in the near Kent JE, Molony V, Robertson IS. Changes in plasma concentrations of cortisol in lambs of three ages in the first three hours after three future, but the use of local anaesthetic given into the scro- methods of castration and tail docking. Research in Veterinary tal neck followed by ring castration plus tailing, which significantly reduces the cortisol distress response, should Kent JE, Molony V, Robertson IS. Comparison of the Burdizzo and be encouraged. Tailing will be necessary for the immedi- rubber ring methods for castrating and tail docking lambs. Veteri-nary Record 136, 192-196, 1995.
ate future. It can be done using a ring or iron as both Lester SJ, Mellor DJ, Holmes RJ, Ward RN, Stafford KJ. Behavioural methods cause a response similar to handling.
and cortisol responses of lambs to castration and tailing using dif- Animal welfare organisations and marketing chains are ferent methods. New Zealand Veterinary Journal 44, 45-54, 1996.
influencing farm management practices and may deter- Lester SJ, Mellor DJ, Ward RN. Effects of repeated handling on the mine what methods of castration and tailing are accept- cortisol responses of young lambs castrated and tailed surgically.
New Zealand Veterinary Journal 39, 147-149, 1991a.
able in specific markets. It is important for research to Lester SJ, Mellor DJ, Ward RN, Holmes RJ. Cortisol responses of young identify practical methods which both satisfy the require- lambs to castration and tailing using different methods. New Zea- ments of the market and meet our ethical responsibility land Veterinary Journal 39, 134-138, 1991b.
to devise and use approaches which are as welfare-friendly Mazzaferro EM, Nippo MM, Fleming MW, Gross WA, Rhodes III RA.
Physiologic and behavioral changes associated with different meth- ods of tail-docking lambs. Journal of Animal Science 71 (Suppl.
1), 118, 1993.
Acknowledgements
McCormack K, Brune K. Dissociation between the antinociceptive and anti-inflammatory effects of the non-steroidal anti-inflammatorydrugs. Drugs 41, 533-547, 1991.
We are grateful to MAF Policy for providing financial McMeekan CM, Stafford KJ, Mellor DJ, Bruce RA, Ward RN, support for our castration and tailing studies, to Dr A.C.D.
Gregory NG. Effects of regional analgesia and/or a non-steroidal Bayvel for helpful discussion and to Associate Professor anti-inflammatory analgesic on the acute cortisol response todehorning in calves. Research in Veterinary Science 64, 147-150, Alex Davies and Ms Jean Arnott for preparing Figure 1.
McQuay HJ, Carrol D, Moore RA. Postoperative orthopaedic pain - the effect of opiate premedication and local anaesthetic blocks.
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Accepted for publication 8 December 1999.

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