Welfare consequences of mulesing of sheep

Mulesing is traditionally performed on approximately 80% of Merino wool-producing sheep in Australia. Mulesing produces a stress response that persists for 24 to 48 hours. Behavioural changes indicative of pain and discomfort resolve within 24 and 48 hours, respectively. Reductions in weight gain may persist for 14 days. The acute stress response to mulesing has been shown to be similar to that produced by shearing, castration and mild flystrike, but mulesing has a longer duration of response (24 to 48 hours) than shearing (1 hour) or knife castration (8 to 24 hours), whereas flystrike response persists for the duration of infection. Theoretically, if mulesing were not used, with Merino sheep of existing genetics, increased chemical use and flock inspections could keep flystrike rates to approximately equivalent to present levels in some production systems. Increased handling events for chemical preventative application would represent a mild stressor for sheep, but cumulatively not more than that of mulesing. If producers were able and prepared to sufficiently increase resources into alternative anti-flystrike methods, then the welfare of Merino sheep would probably be equivalent or better to that of today. If constraints such as property size or finances dictate a sub-optimal level of flystrike prevention and treatment, then animal welfare will unquestionably be worse. The result of that equation would depend on individual flock managers, the physical characteristics of their production system, the profitability of their business, and seasonal variations in flystrike risk. It is likely that there would be some occasions when flystrike would increase. This highlights the need for alternative strategies, such as genetic selection, to reduce the susceptibility of Australian Merino sheep to flystrike.     

Wound healing after mulesing and other options for controlling breech flystrike in Merino lambs: quantitative and semiquantitative analysis of wound healing and wound bed contraction

Background A two‐part study examined wound healing and contraction occurring after mulesing and two alternative methods of preventing breech flystrike in sheep. Objective To quantify wound healing using a scoring system and to assess the contractility of the wound bed of the breech after mulesing, cetrimide‐intradermal treatment and application of clips. Method The study group of 30 mulesed, 30 cetrimide‐intradermal treated, 30 control and 10 clip‐treated sheep were humanely killed at six time points from 3 to 47 days after each treatment. Wound healing post treatment was assessed using a scoring system, and contractility was assessed by the quantification of myofibroblast expression. Statistical analyses allowed comparisons of temporal wound healing and contraction between treatment groups. Results Mulesing wounds healed faster in the first 11 days, but by 19 days wound healing was similar between the mulesing and cetrimide‐intradermal groups. By 32 days, all three treatment groups had similar wound healing scores. There was greater myofibroblast expression in the mulesing group in the first 11 days after treatment, but by 19 days expression was similar in both the mulesing and cetrimide‐intradermal groups. The clip group had significantly less myofibroblast expression from 32 days after treatment. Conclusion Wound healing is initially most rapid after mulesing, but there are similar wound healing scores in the mulesing and cetrimide‐intradermal treatment groups by 19 days. Both mulesing and the cetrimide‐intradermal treatment induce a similar amount of wound bed contraction, with less contraction observed after application of clips.     

Effect of plastic occlusive clips used as an alternative to mulesing on breech conformation, body weight and survival of Merino lambs

Objective To determine the effect of applying plastic clips to the breech and tail of lambs on the perineal and tail bare areas, breech wrinkle, dag (faecal) accumulation, urine stain, body weight and survival of lambs, compared with unclipped, unmulesed lambs and mulesed lambs. Method The study was conducted on five commercial wool‐growing farms in southern Australia. On each study site lambs (2–12‐weeks‐old) were divided into three groups: (1) unclipped, unmulesed control (tail dock only); (2) treated with clips; and (3) treated with the mules operation. Evaluations of effects, including visual scoring, bare area measurements and body weight, were performed before treatment and on or approximately days 30, 60, 90 and 180 after treatment. On each occasion, lambs were recorded as either present or absent to allow estimates of survival. Results The clip treatment increased the size of the perineal and tail bare areas compared with the unclipped, unmulesed control lambs (P < 0.05), although the increases were less than in mulesed lambs (P < 0.05). The clips reduced breech wrinkle, dag and urine stain to levels partway between those recorded in the unclipped, unmulesed controls and the mulesed lambs (P < 0.05). Clipped lambs weighed more than mulesed lambs after treatment (days 30–90 P < 0.001; day 180 P < 0.01) and had higher cumulative percentage survival to 90 days after treatment (P = 0.03). Conclusions The clips successfully modified the breech region of lambs, although the changes were less than with mulesing. The clips did not reduce the body weight of lambs, compared with the unclipped, unmulesed control lambs, and improved 90‐day cumulative percentage survival compared with mulesed lambs.     

Impact of topical anaesthesia on pain alleviation and wound healing in lambs after mulesing

Objective     To investigate the impact of using the topical anaesthetic preparation Tri-Solfen® on pain alleviation and wound healing in lambs undergoing mulesing.
Design   Three separate trials, placebo controlled and/or randomised, were carried out over a 5 month period on three mobs of between 60 and 263 merino lambs undergoing routine mulesing.
Procedure     Wound pain was assessed using 10 and 75 g calibrated Von-Frey monofilaments to determine sensitivity to light touch and pain stimulation over a 4 to 8 h period. Pain-related behaviour was documented by trained, blinded observers using a numerical rating scale. Wound healing rates were determined using scaled digital photography and image analysis software to calculate contraction in wound surface area 2 and 4 weeks after mulesing.
Results     There was rapid (3 min) and prolonged (up to 8 h) wound analgesia as shown by pain response scores (P ≤ 0.01), with absent or significantly diminished primary and secondary hyperalgesia (P ≤ 0.01) and significant reduction in pain-related behaviour (P < 0.001) in treated versus untreated lambs. In addition there was improved wound healing in the treated lambs (P ≤ 0.05).
Conclusion     Tri-Solfen® effects rapid and prolonged wound analgesia, reduction in pain-related behaviour and improved wound healing in lambs undergoing routine mulesing, providing effective alleviation of pain associated with routine mulesing in sheep.     

The effect of a topical anaesthetic formulation, systemic flunixin and carprofen, singly or in combination, on cortisol and behavioural responses of Merino lambs to mulesing

OBJECTIVE: To determine the pain responses of lambs to mulesing, and the effectiveness of potential analgesic treatments. PROCEDURES: Merino lambs (n=64) were allocated at 5 weeks of age to eight treatment groups: 1) sham mules; 2) conventional mules; 3) topical anaesthetic, incorporating lignocaine, bupivicaine, adrenaline and cetrimide, applied immediately after mulesing; 4) flunixin + topical anaesthetic, with flunixin administered 2.5 mg/kg s.c. 90 min before mulesing; 5) carprofen + topical anaesthetic, with carprofen administered 4 mg/kg s.c. 90 min before mulesing; 6) carprofen, administered as above; 7) flunixin, administered as above; and 8) carprofen + flunixin, administered as above. Plasma cortisol was measured at 0, 0.5, 6, 12 and 24 h relative to mulesing. Animal behaviour, including posture, was recorded for 12 h after mulesing. RESULTS: The conventional mules lambs exhibited large increases in plasma cortisol, reduced lying and increased standing with a hunched back compared with sham mules animals. Topical anaesthetic reduced the cortisol peak to mulesing and hunched standing, and increased lying compared with the conventional mules treatment, but generally did not result in values equivalent to sham mules animals. Carprofen, flunixin, and carprofen + flunixin treatments did not reduce the cortisol response to mulesing but substantially ameliorated some changes in behavioural postures. Flunixin + topical anaesthetic reduced the cortisol peak following mulesing and substantially ameliorated most changes in behavioural postures. Carprofen + topical anaesthetic abolished the cortisol peak following mulesing and substantially ameliorated most changes in behavioural postures. All mulesed animals lost weight in the week after mulesing regardless of analgesic administration, but there were no significant differences in growth rate between any of the eight treatments over the 3 weeks after mulesing. CONCLUSIONS: Analgesics can moderate the pain response of lambs to mulesing. The welfare outcome for lambs of mulesing could be improved by use of a combination of local anaesthetic and long acting non-steroidal anti-inflammatory drug.     

Prevalence of breech-strike in mulesed, clipped and unmulesed Merino hoggets in south-eastern Australia

Objective To compare the prevalence of breech flystrike (‘breech‐strike’) on 12–20‐month‐old Merino hoggets that were mulesed, had breech and tail clips applied (‘clipped’) or were left unmulesed but treated strategically with long‐acting insecticide. Design A cohort study on three farms in southern Victoria. Methods Three treatment groups were established at lamb marking on each farm. The unmulesed group was treated with dicyclanil when 12 months old in September or October (‘early‐season treatment’). The prevalence of breech‐strike and key risk factors, including soiling of the breech with faeces (‘dag’) and urine (‘stain’), and breech wrinkle, were compared between the groups. Results Over all the farms, breech‐strike occurred on 1.1% of mulesed sheep and 7.7% of clipped sheep. Clipped sheep had a relative risk of breech‐strike of 18.2‐, 16.8‐ and 3.0‐fold that of mulesed sheep on the three farms. Unmulesed sheep treated with dicyclanil had a similar prevalence of breech‐strike to that of mulesed sheep (overall 0.9%, range 0–2.5%), but had significantly more dag, stain and wrinkle. Conclusion Early‐season treatment of unmulesed sheep prevented most breech‐strikes during the spring and early summer, and offers a short‐ to medium‐term option for the control of breech‐strike in south‐eastern Australia. There were some benefits associated with using clips, namely less dag and stain, and a shorter time spent crutching. However, to control breech‐strike the clipped sheep should be treated the same as unmulesed sheep. Reducing the prevalence and severity of dag will be a major component of strategies to control breech‐strike of Merinos in this region.     

Effectiveness of a non-surgical alternative to the Mules operation in sheep

Objective To measure changes to the perineal bare area, local tissue reaction and healing responses of young sheep, following intradermal administration of cetrimide and polyvinylpyrrolidone (PVP), with and without ethanol, to the breech and tail. Method A needle‐less injector was used to deposit formulations containing 40 g/L cetrimide and 30 g/L PVP (group 2) or 20 g/L cetrimide, 30 g/L PVP and 15 g/L ethanol (group 3), within the dermis of the tail and the region surrounding the perineal bare breech area of groups (N = 8) of Merino weaner sheep. The dimensions of the perineal bare area (length, width and diagonal distances left and right) and tail width were recorded before and at intervals after treatment for 60 days. Observations of swelling and bruising and scab formation at the treatment sites were recorded for up to 35 days after treatment. Rectal temperatures were monitored for up to 35 days after treatment and bodyweight for up to 60 days after treatment. An untreated control group (group 1) was included. Results Comparison of day ‐3 and day 35 measurement data showed that both treated groups had significantly (P < 0.05) wider breech bare areas compared to the untreated controls and that group 2 sheep had significantly (P < 0.05) longer breech bare areas compared to group 3 sheep or to the untreated controls, which were not significantly different. At this time scabs were still firmly in place on many treated sheep. At day 35 there was no increase in tail bare area caused by either treatment. By day 60 there was no significant difference between the treated and control groups in either the breech or tail regions indicating that the changes present at day 35, were not permanent. Mean weight gain in the groups throughout the 60‐day interval was unaffected by treatment. Intradermal treatment was associated with a significant elevation in body temperature. This effect lasted for 3 days and was associated with signs of discomfort and depressed appearance in at least some of the treated sheep. Bruising was mild to severe in all treated sheep within two days of treatment but was not evident in any sheep by day 21. Mild to moderate swelling was also associated with treatment but was not uniform across sheep in the groups. The tail of one sheep was severely swollen for several days. Swelling remained obvious in most treated sheep until day 14 but was not present at day 21. Conclusion Under the conditions of this study intradermal injection of cetrimide had no permanent effect on bare area measurements on the breech or the amount of wool‐bearing skin on the tail. It also caused signs of discomfort and pain that raise welfare concerns.     

Field trials of a formulation containing moxidectin and 6 in 1 vaccines for sheep

Objective: To assess the efficacy and safety of a formulation containing moxidectin and 6 in 1 vaccine in sheep under field conditions.
Design: Efficacy and safety study.
Animals: Two hundred and five crossbred Merino lambs and two hundred and eight Merino ewes were used in the studies.
Procedure: A formulation was made for the simultaneous treatment of sheep with moxidectin and immunisation against clostridial diseases and caseous lymphadenitis. The efficacy against nematodes, vaccine response and safety were assessed.
Results: Effective control of nematodes and responses to antigens were achieved following subcutaneous administration. The formulation was safe to administer; occasional minor tissue reactions were evident, but no other adverse effects of treatment were observed in either pregnant ewes or lambs, using either the recommended dose, or an overdose of the formulation.
Conclusion: Administration of a formulation containing moxidectin, five clostridial antigens and caseous lymphadenitis antigen proved safe and efficacious under field conditions.     

Evaluation of a regional nerve block with an experimental formulation of encapsulated lidocaine in sheep

ObjectiveTo compare the duration of nociceptive and proprioceptive blockade from an experimental encapsulated lidocaine preparation with that of conventional lidocaine.Study designProspective, blinded, randomly assigned, crossover study.AnimalsA total of six adult Dorset ewes, American Society of Anesthesiologists physical status I or II, weighing 60.4 ± 18.0 kg (mean ± standard deviation).MethodsUnder general anesthesia and guided by electrolocation, the common peroneal nerve was blocked unilaterally with encapsulated lidocaine (0.1 mL kg^–1, 200 mg mL^–1) or conventional lidocaine hydrochloride (0.1 mL kg^–1, 20 mg mL^–1). Each sheep was administered both treatments with an interval of 2 weeks between treatments. Nociception and proprioception were scored (scales of 0–3) before anesthesia, at 0.5, 1, 2, 4, 8, 12, 16, 20 and 24 hours after completion of local anesthetic injection, and every 12 hours thereafter for 9 days. Nociceptive and proprioceptive blockade ended the first time each score reached ‘0’; maximum blockade duration was considered and recorded to be the time point immediately prior to this end point. Significance of differences between treatments for duration of blockade was tested with the Wilcoxon rank-sum test. Effects of time and treatment on nociceptive and proprioceptive blockade were evaluated with mixed-effect models. Significance was set at p < 0.05.ResultsCompared with conventional lidocaine, nociceptive blockade lasted 88 hours longer with encapsulated lidocaine (p = 0.008), and proprioceptive blockade lasted 6 hours longer (p = 0.03). Significant effects of time (p < 0.0001), treatment (p = 0.0435) and treatment1time (p < 0.0001) were observed for nociception. Significant effects of time (p < 0.0001) and treatment1time (p = 0.0058) were observed for proprioception.ConclusionEncapsulated lidocaine produced nociceptive blockade with a duration substantially longer than conventional lidocaine.Clinical relevanceSustained-release encapsulated lidocaine alleviates pain and may minimize systemic analgesic use.     

Use of analgesic drugs for pain management in sheep

Awareness of pain and its effects is increasing within the veterinary profession, but pain management in food animals has been neglected. Sheep seldom receive analgesics despite various conditions, husbandry practice and experimental procedures being known to be painful, e.g. footrot, mastitis, vaginal prolapse, castration, vasectomy, penis deviation, and laparoscopy. The evidence supporting use of analgesic drugs in this species is reviewed here. Opioid agonists are of dubious efficacy and are short acting. α?-agonists such as xylazine are good, short-lived analgesics, but induce hypoxaemia. Non-steroidal anti-inflammatory drugs (NSAID) such as ketoprofen provide long-lasting analgesia, but not as marked as that from α?-agonists; they should be more widely used for inflammatory pain. Local anaesthetics reliably block pain signals, but may also induce motor blockade. Balanced analgesia using more than one class of drug, such as an α? agonist (e.g. medetomidine) and N-methyl-D-aspartate antagonist (e.g. ketamine), with the combination selected for the circumstances, probably provides the best analgesia for severe pain. It should be noted that there are no approved analgesic drugs for use in sheep and therefore the use of such drugs in this species has to be off-label. This information may be useful to veterinary practitioners, biomedical researchers, and regulators in animal welfare to develop rational analgesic regimens which ultimately may improve the health and welfare of sheep in both farming and experimental conditions.     

三苯双脒肠溶片在羊体内药物代谢动力学试验

为研究三苯双脒在绵羊体内动态变化的规律,采用方法如下:绵羊1次口服给药60、120、180 mg/kg体重3个剂量组,依据消除速率常数、吸收率常数、达峰时、血药浓度-时间曲线等主要药动学参数,经上海宏能软件有限公司开发的临床药物代谢动力学软件进行数据分析,符合血管外给药一级吸收一室模型,主要药动学参数为:吸收率常数Ka=0.15129h,t1/2Ka=4.74h,消除速率常数Ke=0.082 121h,t1/2Ke=8.46h,t1/2=19.03 h,达峰时tmax=8.0 h,Cmax=6257μg/L,血药浓度-时间曲线下面积AUC=300 51μg/L.h。三苯双脒肠溶片在羊体内吸收快、半衰期长等特点。说明三苯双脒肠溶片在药效试验剂量范围内比较安全。     

A discriminatory study of a pharmacokinetic model for intramuscular gentamicin in sheep

The resulting serum concentrations were measured in six ewes after intramuscular administration of 10 mg/kg of gentamicin. The model providing the best fit for the experimental data was determined both by linear regression analysis between the experimental and theoretical values and by means of the Minimum Akaike Information Criterion Estimation (MAICE) test.Linear regression analysis showed certain differences favouring the monocompartmental model although the advantage was not conclusive. The MAICE test, however, permitted a clear discrimination in favour of the same model. When linear regression analysis is not conclusive, the MAICE test represents a good alternative.     

阿维菌素长效注射液(油悬剂)对绵羊痒螨的疗效试验

为了研究阿维菌素长效注射液(油悬剂)对绵羊痒螨疗效,将60只自然感染痒螨绵羊随机分为3组,每组20只。第1组每千克体重颈部皮下注射1 mg的阿维菌素油悬剂,第2组注射0.2 mg的阿维菌素普通注射液,第3组为不给药对照组。在给药后第7、14、21、28、35、42、49、56、63、70天对所有绵羊进行螨虫检查和计数,每天观察病变。结果表明:给自然感染痒螨的绵羊皮下注射1 mg/kg的阿维菌素长效注射液(油悬剂)可在给药后7 d内将痒螨完全杀灭,在给药后63 d内防止绵羊被痒螨再感染,其持效期远长于阿维菌素普通注射液(约为14 d)。     

Measurement of progesterone in sheep using a commercial ELISA kit for human plasma

Determination of serum or plasma progesterone (P4) concentrations is important to recognize pregnant and non-pregnant ewes, and also to predict the number of carried lambs. The 2 most common methodologies for the detection of plasma P4 are radioimmunoassay (RIA) and enzyme immunoassay (EIA). RIA is very expensive, and not all laboratories are equipped to perform this test; EIA is commercially available for human use, but only a few companies produce species-specific kits, which are expensive. We verified for ovine plasma a less expensive and easily available ELISA kit (DiaMetra) designed to quantify P4 in humans. Pools of ovine and human plasma were used to compare repeatability, accuracy, sensitivity, and stability of P4 measured by the DiaMetra kit. Repeatability data were within 15%, and accuracy values were ~90% for both plasma matrices. Stability data showed a loss of <20% for freeze–thaw and <30% for 30-d storage. All parameters were acceptable under international guidelines for method validation. The human ELISA kit was used successfully to quantify plasma P4 in 26 ewes during pregnancy until delivery. P4 concentrations were also correlated with the number of carried lambs.     

Assessment of the long‐acting ivermectin formulation in sheep: Further insight into potential pharmacokinetic interactions

The aim of the current study was to evaluate the in vivo pharmacokinetic of ivermectin (IVM) after the administration of a long‐acting (LA) formulation to sheep and its impact on potential drug‐drug interactions. The work included the evaluation of the comparative plasma profiles of IVM administered at a single therapeutic dose (200 μg/kg) and as LA formulation at 630 μg/kg. Additionally, IVM was measured in different gastrointestinal tissues at 15 days posttreatment with both IVM formulations. The impact of the long‐lasting and enhanced IVM exposure on the disposition kinetics of abamectin (ABM) was also assessed. Plasma (IVM and ABM) and gastrointestinal (IVM) concentrations were analyzed by HPLC with fluorescent detection. In plasma, the calculated C_max and AUC_0‐t values of the IVM‐LA formulation were 1.47‐ and 3.35‐fold higher compared with IVM 1% formulation, respectively. The T_1/2ab and T_max collected after administration of the LA formulation were 2‐ and 3.5‐fold longer than those observed after administration of IVM 1% formulation, respectively. Significantly higher IVM concentrations were measured in the intestine mucosal tissues and luminal contents with the LA formulation, and in the liver, the increase was 7‐fold higher than conventional formulation. There was no drug interaction between IVM and ABM after the single administration of ABM at 15 days post‐administration of the IVM LA formulation. The characterization of the kinetic behavior of the LA formulation to sheep and its potential influence on drug‐drug interactions is a further contribution to the field.