Does UK licensed NSAID administration reduce signs of postoperative pain in calves castrated without local anaesthesia?

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The evidence
Twenty studies were critically appraised; all were controlled trials and of these 17 were randomised. Only NSAIDs licensed for use in cattle in the UK were included in the search strategy and in appraised papers. Direct comparison between the studies was made difficult by variations in calf age*, castration method, NSAID type, dosage, administration and timing of administration. Many studies also used relatively small sample sizes and did not report power analyses when determining sample size or CI when reporting data, possibly reducing the reliability of their results. Additionally, some studies also investigated variables which were not relevant to the PICO question such as pain associated with branding and the effect of local anaesthetic on pain indicators ( Webster et al., 2013); these studies were included but the treatments not relevant to the PICO question were excluded from the appraisal. Studies assessed pain response to NSAIDs by measuring physiological parameters (e.g. cortisol concentrations, APP concentrations, ADG, scrotal or rectal temperature) and behavioural parameters (e.g. standing, lying and stepping behaviour, motion index, gait, eating and drinking and specific, discrete behaviours such as tail flicking and lesion-licking).
A significant reduction in pain associated with castration was defined as improvements in both physiological and behavioural pain indicators, and no reduction in pain was defined as no significant improvements in either physiological or behavioural indicators. Some studies were ranked as intermediate

Physiological indicators of pain/inflammation
• Fibrinogen and haptoglobin concentrations were unaffected by meloxicam administration • No difference in ADG between BAN and BAN + M groups

Behavioural indicators of pain/inflammation
• BAN + M group took fewer steps than BAN group on days 7 and 15 and had significantly more lying bouts per day on days 13 and 14 than BAN group • Overall meloxicam administration did not result in major improvements in behavioural pain indicators Limitations: • Small sample size may reduce reliability of data (no power analysis reported) • No CI reported • Non-blinded study (but behaviour was assessed using accelerometers so lack of blinding may have had less effect) • Blood samples were taken on days 0 (before treatment), 14 and 28 which may have been too infrequent to observe short-term changes in fibrinogen and haptoglobin concentrations, especially during the acute inflammatory period within the first 14 days following castration • Unknown when on day 0 meloxicam was administered, i.e. before, concurrently to or after castration • Unclear significance of BAN + M group taking fewer steps than BAN group -BULL group took the most steps per day overall which would suggest that more steps is indicative of less pain but this could also have been due to cows in the pasture being in oestrus which was not measured in the study 20 Subsets of cow-calf pairs representing each treatment group were randomly selected to be used for behavioural analyses -20 calves were assessed for behavioural changes, 15 calves were used to assess cow-calf proximity and 36 calves were used to measure home range.

Doses and administration
• Meloxicam (0.5 mg/kg) -subcutaneous injection (timing of administration not mentioned) • Lactated Ringers solution (dose not given) -subcutaneous injection (timing of administration not mentioned)

Study design: Randomised controlled trial
Outcome studied: Physiological indicators of pain/inflammation • Objective assessment of pain sensitivity before and after castration -maximum pressure exerted before animal responded • Objective assessment of maximum scrotal temperature and weight (to determine ADG) before and after castration • Subjective assessment of wound swelling and wound healing before and after castration Behavioural indicators of pain • Subjective assessment of behaviours inc. suckling, lying, walking, lesion-licking, foot stamping and tail licking before and after castration (interobserver reliability = 0.93 and intra-observer reliability = 0.90) • Objective assessment of cow-calf proximity (after castration) and home range (daily before and after castration)

Physiological indicators of pain/inflammation
• CAST + FLU had lower mean cortisol concentrations 2, 3 and 4 hours postcastration than CAST + PLBO, suggesting flunixin controls the initial cortisol spike associated with castration and longer-term cortisol levels • CAST + FLU (73 ng×h/ml (95% CI 45 -102)) had smaller cortisol area under the curve than CAST + PLBO up to 8 hours postcastration (157 ng×h/ml (95% CI 128 -186)) • No effect of flunixin on substance P concentrations • CAST + FLU had higher maximum, mean and minimum ocular temperatures than CAST + PLBO and SHAM + PLBO following castration and treatment (authors hypothesised reduced ocular temperature with flunixin)

Behavioural indicators of pain
• CAST + PLBO and CAST + FLU placed more force on front limbs than SHAM + PLBO, suggesting gait modification in response to castration pain; CAST + FLU had a numerically smaller mean force difference between fore-and hindlimbs than CAST + PLBO • SHAM + PLBO had a lower total impulse (i.e. traveled more quickly) than CAST + PLBO and CAST + FLU but no significant difference between CAST + PLBO and CAST + FLU • No significant difference in stride lengths between treatment groups

Limitations:
• Small sample size may reduce reliability of data (no power analysis for sample size reported) • First ocular temperature reading was taken 2 hours postcastration preventing measurement of acute changes before this; ocular temperature measurement as pain assessment is not well understood and optimal sampling intervals are not well described

Outcome studied: Physiological indicators of pain/inflammation
Objective assessment of liveweight change and serum cortisol concentrations on days -6, -1, 1, 2, 6, 10, 13; serum cortisol was also measured immediately before castration Behavioural indicators of pain • Subjective assessment of crush score (observing the animal for 60 seconds in the crush without head restraint), recorded on days -6, -1, 1, 2, 6, 10, 13 • Subjective assessment of baulk score by a single observer when entering the weighing area for the first time (recorded on days -6, -1, 1, 2, 6, 10, 13) o Non-baulker -enters voluntarily when the gate opens, or a light tap on the rump is required for the animal to enter o Baulker -a hard slap on the rump or tail twisting is required for the animal to enter • Blood samples were taken on days -6, -1, 0 (cortisol only), 1, 2, 6, 10 and 13 -these sampling intervals may have been too wide to detect some changes, especially in the acute phase immediately following castration • Some calves were too large for the pressure matscomplete strides and two footfalls per timepoint could not be recorded for each calf, limiting stride length evaluation • Calves were only studied for 72 hours postcastration so longer-term pain responses were not investigated, although due to its kinetics, flunixin was unexpected to affect pain responses past this time • Behavioural assessment of pain was limited and only included gait parameters rather than e.g. standing, lying and postural behaviour Limitations: • Salivary cortisol may be less sensitive than plasma cortisol to adrenal activity • High inter-assay coefficient of variation (24.2%) and variation between individuals in substance P measurements could have masked treatment effects • Substance P sampling times (immediately before castration and at 60, 90, 120, 180 minutes and 1, 2, 3 and 7 days after castration) may not have been adequate to detect differences between treatments • Differences in ADG (0.2 kg/day) and in scrotal and rectal temperatures between KN-NM and KN-M may lack biological significance as they are small • Power analysis indicated that 6-12 calves minimum per treatment were required to detect differences in salivary cortisol and tail flicking between treatments; six calves per group were assessed for behaviour and 12 (i.e. the whole group) were assessed for salivary cortisol so the sample size may have been too small to accurately detect differences • No power calculations for other behavioural parameters so sample size may have been too small to detect differences • CI for pain assessment not reported • Behavioural parameters may not be sensitive enough to pain and individual variation may have masked treatment effects; sampling times may have been insufficient to observe differences between groups (animals observed for a 2 hours period on day 0 and every 10 minutes for a 4 hour period on days 1, 2, 3 and 7)

Outcome studied: Physiological indicators of pain/inflammation
Objective assessment of salivary cortisol concentration, blood parameters (substance P, haptoglobin, SAA, CBC), scrotal and rectal temperatures and ADG before and after castration Behavioural indications of pain • Subjective assessment by blinded observers using video footage of standing, walking, lying, suckling behaviour and frequency of tail flicking, head turning, lesion-licking and foot stamping before and after castration (intra-and interobserver reliability = 0.90 and 0.91 respectively) • Objective assessment of stride length and standing and lying behaviour before and after castration

Physiological indicators of pain/inflammation
• M calves had lower substance P concentrations than NM calves 7 days postcastration; also tended (p=0.06) to be lower 3 days postcastration • M calves had lower WBC count than NM calves • KN-NM calves had higher SAA concentrations than all other groups apart from BA-M where there was no difference Behavioural indicators of pain • Six calves per treatment group were assessed for behavioural changes • NM calves showed more tail flicks than M calves 2-4 hours postcastration but M calves showed more tail flicks than NM calves on day 7 postcastration (thought to be due to effects of meloxicam wearing off) • Tendency for M to have fewer standing bouts, greater lying duration and longer lying bouts than NM calves • M calves spent less time in lateral recumbency than NM calves on day 3

Limitations:
• Not all findings were associated with p < 0.05 and were tendencies rather than statistically significant associations • Numerical differences in standing and lying bouts are small and may lack biological significance • Only six calves per treatment were assessed for behavioural changes • No power calculations for sample sizes required so sample sizes may have been too small to accurately detect differences between treatment groups • No CI reported for pain assessment Outcome studied: Physiological markers of pain/inflammation • Objective assessment of saliva and hair cortisol, blood parameters (SAA, haptoglobin and WBC count), scrotal area temperature and rectal temperature before and after castration • Objective assessment of scrotal circumference after castration • Objective assessment of weight before and after castration to determine ADG Behavioural indicators of pain • Subjective assessment by blinded assessors using video footage of pain-associated behaviour postcastration (tail flicks, foot stamping, head turning, lesion-licking and duration of standing, lying, walking and eating) after castration • Objective assessment of feeding behaviour (measurement period not stated) • Objective assessment of stride length and standing and lying behaviour before and after castration Plasma meloxicam concentrations and behavioural and escape responses during castration were also measured; these results were not appraised as they are not relevant to the PICO question Main findings: (relevant to PICO question):

Physiological indicators of pain/inflammation
• Salivary cortisol concentrations were lower in MR calves than NR calves 2, 4 and 48 hours postcastration but no differences between groups in hair cortisol concentrations minutes before castration and 1, 2, 3, 4, 5 and 6 days postcastration

Study design: Controlled trial
Outcome studied: Physiological indicators of pain/inflammation • Objective assessment of scrotal temperature (using thermographic imaging) and salivary cortisol concentrations before and after castration • Objective assessment of blood parameters (WBC count and N:L) after castration • Objective assessment of weight before and for several weeks after castration to obtain ADG Behavioural indicators of pain Objective assessment of feed intake and feeding behaviour (timeframe measurements were taken in not stated)

Main findings: (relevant to PICO question):
• Blood and saliva samples were taken from a subset of animals (n = 23 and n = 24 respectively); these groups contained calves from each treatment group • Salivary cortisol tended (p = 0.08) to be lower in KP calves than PS calves at 5 hours postcastration in experiment 1 • No other significant effect of ketoprofen on physiological or behavioural indications of pain in either experiment

Limitations:
• Limited behavioural assessment • Blood and saliva samples were only taken from a subset of animals so there may have been inadequate statistical power and associations may have been missed (no power calculations are reported) • No CI reported • Some results were trends and not statistically significant • Ketoprofen chiral inversion varies between individuals depending partially on age and physiological statusvariation in inversion contributes to variation in pharmacological properties and ability to inhibit prostaglandin production so ketoprofen may not be an effective analgesic in certain populations

Olson et al. (2016)
Population: Holstein bull calves aged 4-5 months old (Canada) Limitations: • CI not stated for individual results • Only 10 hours of heart rate data was analysed as no data could be obtained for many animals past 10 hours

Outcome studied: Physiological indicators of pain/inflammation
• Objective assessment of blood parameters (WBC count, N:L, plasma cortisol and haptoglobin concentrations) and rectal temperature before and after castration • Objective measurement of weight before and after castration to obtain ADG Behavioural indicators of pain Subjective assessment by blinded observers using video footage of active pain avoidance behaviours (attempts to stand and lie, restlessness, kicking/foot stamping, wound licking, stretching) and postural behaviours (lying, standing and walking behaviours) for 12 hours after castration Limitations: • One SC calf and one BS calf were omitted from behavioural analysis due to >50% postural data being missing due to rainfall making footage difficult to view, reducing the sample size • Rainfall may have made behavioural analysis more difficult even in calves which had more complete data recorded • Experiment was carried out in five cohorts due to logistical limitations; there were statistically significant differences in normal standing, ventral lying and normal walking behaviour between cohorts (thought to be due to differences in weather conditions) which may have masked more subtle treatment-associated behavioural changes • Flunixin can be irritating to tissues so is normally administered intravenously -iatrogenic scrotal irritation may have caused increased pain avoidance behaviours in the BF calves • Only subjective measurement of pain-related behaviour  up to 7 hours after castration and weight for several weeks after castration • Subjective assessment of scrotal healing (scoring system) after castration Behavioural indications of pain Subjective assessment by a blinded observer of behaviour postcastration, including standing and lying behaviour, ruminating behaviour, walking behaviour, feeding and drinking, tail flicking and tucking, leg lifting and kicking Main findings: (relevant to PICO question):

Physiological indicators of pain
• No significant differences between calves given ketoprofen and control calves in cortisol or haptoglobin concentration • BK and SK calves had higher creatine kinase concentrations than the control groups at 7 hours postcastration and exceeded reference intervals • SK calves had lowest total protein levels and PCV, suggesting ketoprofen increased blood loss • No effect of ketoprofen on overall liveweight change or wound score

Behavioural indicators of pain
• SK calves spent more time feeding than SS calves • Ketoprofen-treated calves tended to show fewer tail movements than saline-treated calves

Limitations:
• No comparison to uncastrated control calves administered ketoprofen and saline • Ketoprofen takes some time to provide analgesia so more behavioural effects may have been seen if there was a longer time between administration and castration (however the authors did this intentionally to mimic what is likely to occur in industry) • There were occasions when the blinded observer was effectively unblinded due to the presence of blood on the hindlegs of some surgically castrated bulls • Only subjective measurement of pain-related behaviour • Small sample size may reduce reliability of data (no power calculations reported) • No CI reported 2. Band castration with meloxicam (BAND-MEL) 3. Sham castration with placebo (SHAM) Numbers of animals in specific groups were not given Dose and administration

Study design: Randomised controlled trial
Outcome studied: Experiment 1

Physiological indicators of pain/inflammation
Daily weighing (objective measurement) before and after castration to determine ADG Behavioural indicators of pain • Subjective assessment of response to restraint (chute score) before, during and after castration; standing, walking, lying, eating and drinking behaviours before and after castration using video footage by blinded observers • Objective assessment of exit velocity after taking chute score (before and after castration)

Experiment 2 Physiological indicators of pain/inflammation
• Objective assessment of blood substance P concentration and rectal temperature before and after castration; • Weight was also measured to obtain ADG but time points for this are not stated Behavioural indicators of pain Subjective assessment of response to restraint (chute score) before, during and after castration Main findings: (relevant to PICO question):

Experiment 1
• No difference in ADG or chute score between BAND-MEL and BAND groups calves; SHAM calves had higher ADG than both groups of banded calves • Meloxicam treatment had no effect on pen feed bunk behaviour within 120 minutes of castration • Smaller proportion of BAND-MEL calves standing immediately postcastration than BAND calves but greater proportion of BAND-MEL calves standing on days 1-3 than BAND calves

Outcome studied: Physiological indicators of pain/inflammation
Objective assessment of blood parameters (CBC, serum haptoglobin and cortisol concentrations and proinflammatory cytokines (TNF-a, IFN-g)) and rectal temperature before and after castration

Main findings: (relevant to PICO question):
• CAS calves had higher cortisol concentrations than MEL and CON groups (CON was lowest) until 4 hours postcastration • CAS calves also had secondary cortisol peak at 2.5 hours which MEL group did not; MEL group showed drop in cortisol levels at 2 hours • No difference in cortisol levels between CAS and MEL calves at 4 hours postcastration • CAS calves had highest haptoglobin levels • MEL calves had lower haptoglobin levels than CON groupalso had least change in haptoglobin compared to baseline values • MEL calves had higher rectal temperature than other groups • CAS calves had higher WBC counts than MEL and CON groups

Limitations:
• Sample size may have been too small to detect all associations (no power analysis reported) • No CI reported • Relatively high inter-assay coefficient of variation for cytokine assessment (<18.1%) which may have masked some treatment effects • Only physiological markers are assessed which are relatively non-specific and are often due to inflammation rather than pain -no assessment of behavioural indicators of pain • Control groups were not given a placebo • Only behavioural indicators of pain were measured and data was only collected until 3 hours postcastration so more chronic pain behaviours could not be observed • Only subjective measurement of pain-related behaviour • Female calves were used as the control group so some differences between CON and other groups may be affected by sex differences • The calves were separated from their dams for the first time for the study so stress caused by separation may have caused behavioural changes which may have overridden pain-related changes • Wide range of intra-observer reliability for behavioural assessment may have masked some treatment effects and 0 minutes with further ketoprofen given at 24 hours (SK3) Doses and administration Ketoprofen was administered intravenously (IV) through an indwelling jugular catheter at the following doses: • SK1: 3 mg/kg • SK2: 1.5 mg/kg at both time points • SK3: 1.5 mg/kg at -20 and 0 minutes and 3 mg/kg at 24 hours Animals in the S group were given an equivalent volume of 0.9% saline solution

Outcome studied: Physiological indicators of pain/inflammation
• Objective assessment of blood parameters (cortisol, haptoglobin, total antioxidant status, IFN-g, fibrinogen and routine haematology) rectal temperature and dry matter intake (DMI) before and after castration • Calves were weighed before and after castration to determine ADG Behavioural indicators of pain Subjective assessment by a single observer of standing, lying, feeding and ruminating behaviour after castration

Physiological indicators of pain/inflammation
• Ketoprofen administration failed to prevent cortisol increase 0.25-1.5 hours following castration • SK calves had lower mean plasma cortisol concentrations than S group 2-6 hours postsurgery; no difference between SK groups • SK1 and SK2 calves had reduced mean plasma haptoglobin concentrations compared to S animals on day 3 • K calves had higher plasma fibrinogen on day 7 than C or S groups • ADG was lower in S, SK2 and SK3 calves compared to C calves with SK1 values intermediate between C and other groups Behavioural indicators of pain • SK1, SK2 and SK3 calves demonstrated reduced combined abnormal standing activities compared to S calves, which had increased combined abnormal standing activities than C calves • No difference in feeding activities • Ketoprofen administration increased incidence of total rumination compared to S group to similar levels as seen in C group

Limitations:
• Small sample size per treatment may have made associations more difficult to detect (no power analyses reported) • No CI reported • Relatively high inter-assay coefficient of variation for high concentration cortisol assays (19.0%) which may have masked some treatment effects • The behavioural observer was not blinded Doses and administration Meloxicam (0.5 mg/kg) -gel formulation administered buccally adjacent to upper molar teeth 25 minutes before castration

Outcome studied: Physiological indicators of pain/inflammation
• Objective assessment of weight before and after castration to determine ADG • Objective assessment of scrotal diameter and maximum scrotal temperature after castration • Subjective assessment of wound morphology score following castration Behavioural indicators of pain Subjective assessment of walking, standing, lying, postural, eating and drinking behaviours by blinded observers using video footage for 5 hours following castration Main findings: (relevant to PICO question):

Physiological indicators of pain/inflammation
• No effect of treatment on scrotal diameter, wound morphology score or ADG • Lower maximum scrotal temperatures in CBM calves than C calves on day 2

Behavioural indicators of pain
• C calves tended to spend more time walking with a stiff gait than CBM calves • C calves showed more foot stamps than CBM calves

Limitations:
• Relatively small sample size per treatment group. May have made associations more difficult to detect (no power analyses reported) • No CI reported • No assessment of APPs or blood parameters e.g. cortisol • Behaviour was only assessed for 5 hours following castration so only the effects of meloxicam on acute pain can be measured; no information about chronic pain due to inflammation, which NSAIDs are more suited to treating • Several behaviours used in the ethogram could not be included in statistical analysis due to low frequency which may have reduced the sensitivity of pain detection • Only subjective measurement of pain-related behaviour • No placebo was used for calves not given meloxicam • Calves were unweaned so separation from their mothers during castration and sampling may have attenuated pain responses by distracting them from pain, reducing behavioural pain signs (overall limited expression of behavioural pain indicators during observation period)

Webster et al. (2013)
Population: Weaned Holstein-Friesian bull calves aged 2-3 months old (USA) • High variability between individual calves for lying and standing behaviour • Behaviour was mainly assessed subjectively rather than e.g.
using an accelerometer/pedometer to record standing, walking and lying data as in other studies (although behaviours were well defined) • Only plasma cortisol concentration was used as a physiological assessment of pain; cortisol is not pain-specific and can be affected by several other factors inc. handling stress • Plasma cortisol concentration and behaviour were only assessed up to 8 hours postcastration so more chronic changes would not have been observed

Appraisal, application and reflection
All 20 studies appraised were controlled trials, of which 17 were randomised, indicating a relatively high level of evidence. No relevant meta-analyses were found and narrative reviews were excluded due to being widely focused and not showing reproducible search strategies. All studies appraised compared NSAID administration to a control calf castrated without NSAIDs; several studies also included non-castrated or sham-castrated calves to provide a baseline against which pain indicators could be compared. Some studies further improved this protocol by including both medicated and unmedicated sham groups, allowing more accurate differentiation between behavioural and physiological indicators of handling stress versus pain and reducing over-interpretation. Of the studies appraised, 15 included the use of a placebo (saline or lactated Ringer's solution) in approximately equal volume to the NSAID in unmedicated calves to quantify and control for discomfort associated with drug administration. Eleven studies involved blinding, either of personnel recording behavioural observations or measuring physiological pain indicators or both. This was particularly important in behavioural observation to reduce bias as far as possible. However, due to the experimental nature it was sometimes difficult to blind observers, as e.g. surgically castrated calves can be visually differentiated from band castrated calves in the period immediately following castration; Petherick et al. (2014a;and 2014b) also reported that some surgically castrated calves had blood on their hindlimbs, making them easy to identify. Several studies also analysed behavioural parameters using video footage rather than via direct contact with the calves, reducing the likelihood of observer effects on behaviour.
The studies appraised showed mixed results for the efficacy of NSAIDs alone at reducing signs of postcastration pain, although overall 13 out of the 20 studies showed some improvement in pain indicators following NSAID administration. It is important to note that pain is inherently subjective and is therefore difficult to assess objectively; physiological indicators of pain can be measured but some lack specificity to pain alone and can be affected by other factors, e.g. cortisol may increase due to handling stress (Grandin, 1997). Similarly, APPs e.g. SAA and haptoglobin, are indirectly associated with pain through their inflammatory role; as NSAIDs reduce pain associated with inflammation, APP concentrations can be used as a measure of NSAID efficacy but they are not pain-specific. Substance P is involved in nociception, and has been shown to decrease with meloxicam administration following dehorning ( Behaviours such as lesion-licking, foot-stamping, tail flicking and changes in standing and lying behaviour may be more pain-specific (Millman, 2013) than physiological markers, but are more difficult to objectively assess. Several studies used a visual analogue scale to make subjective assessment of pain-related behaviours more repeatable, however in several cases the visual analogue scale was only used to assess intra-castration pain which was beyond the scope of this Knowledge Summary. Objective measurement of behavioural parameters can be obtained using devices e.g. pedometers, accelerometers and pressure mats, which was done by 11 studies. However, these devices generally only collect walking, standing and lying data and not discrete and more pain-specific behaviours such as those described above. Other behavioural changes measured objectively include exit velocity as calves leave the chute and feed intake, however again these are not very pain-specific.
Pain-associated behaviours vary between reports; some authors suggest cattle in pain take fewer steps and show more lying behaviour (Currah et al., 2009;and Laurence et al., 2018), whereas Ting et al. (2003) found that the incidence of combined lying postures in castrated calves was significantly lower than uncastrated calves. This is further confounded by different castration methods causing different behavioural changes: surgical castration may increase standing time and band castration may increase lying time (Roberts et al., 2018). Behavioural indicators of pain may also be difficult to detect as cattle are prey animals and therefore mask pain signs ( found that meloxicam treated band castrated calves spent less time lying than their control counterparts, while meloxicam treated surgically castrated calves spent more time lying than their control counterparts, supporting the idea that different castration methods induce different types of pain and suggesting that meloxicam has some effective analgesic ability for both castration methods. Pain perception in calves may be influenced by age. Bretschneider (2005) reported that castration closely following birth reduces weight loss associated with castration compared to calves castrated later in life; however weight changes are not specific to pain, as reduced weight gain can be influenced by both inappetence caused by pain and reduced testosterone secretion reducing muscle mass, and pain can also motivate calves to suckle more (Meléndez et al., 2018b), increasing weight gain. Bretschneider (2005) also reported that the cortisol response of calves castrated at 6 months or younger tended to be lower than that of older calves and hypothesised that this was related to increased trauma and discomfort due to increased testicular size. However, Stafford & Mellor (2005) reported relatively similar peaks in plasma cortisol concentration for calves aged 6, 21, 42 days, 2-4 months and 5.5 months by castration method used. Despite these possible differences in pain response depending on age, studies investigating calves of all ages up to 1 year were included in the evidence appraisal, as differences in pain response are likely not so significant that they make these studies completely inapplicable to UK practice. Only one study (Meléndez et al., 2018b) investigated a cohort where all calves were below the UK legal age limit for castration without anaesthesia and found meloxicam administration reduced both physiological and behavioural pain signs. Three other studies used calf cohorts where some individuals may have been within the legal age limit (Gellatly et al., 2021;Marti et al., 2018;and Paull et al., 2015) (2 months, 2 months and 7-9 weeks old respectively) and found no improvement in pain indicators following NSAID administration, suggesting that calf age is not the most important factor in NSAID efficacy.
The time at which NSAIDs are administered relative to castration is also likely to affect analgesic efficacy. 12 studies involved NSAID administration before castration and of these, four showed reduced physiological and ; however, it is important to note that these studies both incorporated NSAID administration at several different time points. This could be related to NSAID mechanism of action, as analgesia is provided through COX inhibition reducing prostaglandin synthesis (Day et al., 1987); administration before a painful stimulus may reduce total prostaglandins further than administration after the stimulus when prostaglandin synthesis has already occurred. Ting et al. (2003) reported that calves given either 3 mg/kg ketoprofen 20 minutes before castration or 1.5 mg/kg 20 minutes before followed by 1.5 mg/kg concurrent to castration had reduced mean plasma haptoglobin concentration relative to castrated control calves on day 3, but this was the main significant difference between ketoprofen treated calves, suggesting that time of administration is not the main factor in analgesic effect. Similarly, Laurence et al. (2018) reported that calves administered 0.5 mg/kg meloxicam 30 minutes before castration were more active after castration than unmedicated controls, and that postoperative meloxicam administration at the same dose resulted in calves resting less than controls. These behavioural changes are similar and both meloxicam treated calves had significantly lower plasma cortisol concentrations postcastration than control calves, suggesting both pre-and postoperative meloxicam have some analgesic effect. Repenning et al. (2013) also investigated the effect of several meloxicam doses (1.0, 0.5 and 0.5 mg/kg on days -1, 0 (concurrent with castration) and 1 respectively) and found no significant improvement in pain. This may be because band castration was used, which is thought to cause more chronic pain than the surgical castration used by Laurence  reported that calves treated with 200 mg flunixin showed significantly more pain avoidance behaviours than both calves castrated without flunixin and uncastrated calves. This was the only study which found increased pain following NSAID administration and is thought to be due to tissue irritation due to subcutaneous injection of flunixin into the scrotum. No studies investigating carprofen or directly comparing different NSAIDs were found. Based on the studies appraised, it appears that meloxicam has the best analgesic efficacy for postcastration pain. Ketoprofen has been reported to undergo variable chiral inversion in cattle depending on age and physiological status and these changes are thought to alter its ability to inhibit prostaglandin production (Moya et al., 2014); these changes are not currently well understood, making the efficacy of ketoprofen quite variable. Flunixin does not appear to reliably significantly reduce postcastration pain; Kleinhenz et al. (2018) and Webster et al. (2013) both reported reduced cortisol responses following flunixin administration, but no studies found any improvement in behavioural indicators of pain. However, these results must be taken with caution due to the small number of studies appraised.
The final confounding factor affecting NSAID efficacy is dose and administration. The most common dose for meloxicam was 0.5 mg/kg (seven out of 13 papers investigating meloxicam), and of these five papers found some improvement in pain signs following meloxicam administration. Interestingly, Daniel et al. (2020) used a dose of 2.0 mg/kg meloxicam but found no significant improvement in pain, however this study investigated band castration, which according to the appraised evidence was less amenable to pain relief via NSAIDs. Additionally, limited physiological indicators were assessed and behavioural changes were not clearly interpreted; meloxicam treated calves took fewer steps than unmedicated calves on days 7 and 15 which is It is also possible that NSAIDs generally do not provide adequate analgesia for invasive, painful procedures such as castration as NSAID analgesia displays a ceiling effect (Ong et al., 2007). Combinations of lidocaine and meloxicam or ketoprofen have been reported to be very efficacious in reducing signs of postoperative pain, including the initial acute spike in cortisol associated with castration (Meléndez et al., 2018c;and Webster et al., 2013). However, injection of local anaesthetic into the testes can be painful in itself (Stafford & Mellor, 2005) so more research into this area may be required.
Although not all of the studies appraised are in agreement about the efficacy of NSAIDs in reducing signs of pain postcastration, 13 out of the 20 studies found some benefit to NSAID use and only seven found no benefit, suggesting that on balance NSAID administration is likely to reduce postcastration pain by some degree. Of the NSAIDs investigated, meloxicam appears to be the most effective, although further work in this area is required. Further work is also required to investigate the effect of NSAIDs along with local anaesthetic administered 10-15 minutes prior to castration, as this appears to be the most effective way to mitigate both acute and more chronic pain associated with castration.