Analgesic therapy of beak-trimmed chickens

Nociception in Chicken Embryos, Part III: Analysis of Movements before and after Application of a Noxious Stimulus

Many potentially noxious interventions are performed on chicken embryos in research and in the poultry industry. It is therefore essential and in the interest of animal welfare to be able to precisely define the point at which a chicken embryo is capable of nociception in ovo. The present part III of a comprehensive study examined the movements of developing chicken embryos with the aim of identifying behavioral responses to a noxious stimulus. For this purpose, a noxious mechanical stimulus and a control stimulus were applied in a randomized order. The recorded movements of the embryos were evaluated using the markerless pose estimation software DeepLabCut and manual observations. After the application of the mechanical stimulus, a significant increase in beak movement was identified in 15- to 18-day-old embryos. In younger embryos, no behavioral changes related to the noxious stimulus were observed. The presented results indicate that noxious mechanical stimuli at the beak base evoke a nocifensive reaction in chicken embryos starting at embryonic day 15.

Treatment of Pain in Birds

This article provides an overview of the current understanding of evidence-based clinical analgesic use in birds. The field of avian analgesia has dramatically expanded during the last 20 years, affording more options for alleviating both acute and chronic pain. These options include opioids, nonsteroidal anti-inflammatory drugs, local anesthetics, and/or other drugs like gabapentin, amantadine, and cannabinoids, acting at different points in the nociceptive system thereby helping to provide greater pain relief while reducing the risk of adverse effects when combined.

Local and Regional Anesthesia in Zoological Companion Animal Practice

Local anesthetics provide analgesia and can be incorporated into multimodal anesthetic protocols. They work by blocking the voltage-dependent sodium ion channels along neurons that mediate nociception. Systemically, these drugs can be cardiotoxic in a dose-dependent manner. Lidocaine and bupivacaine are the most commonly used local anesthetics and their use has been reported in all classes of vertebrates. Despite anecdotal reports to the contrary, zoologic companion animals are unlikely to be more susceptible to the cardiotoxic effects of local anesthetics than domestic small animals. Local anesthetics can be clinically useful for analgesia and anesthesia in zoologic companion animal practice.

Prenatal and Early Postnatal Behavioural Programming in Laying Hens, With Possible Implications for the Development of Injurious Pecking

Injurious pecking (IP) represents a serious concern for the welfare of laying hens (Gallus gallus domesticus). The risk of IP among hens with intact beaks in cage-free housing prompts a need for solutions based on an understanding of underlying mechanisms. In this review, we explore how behavioural programming via prenatal and early postnatal environmental conditions could influence the development of IP in laying hens. The possible roles of early life adversity and mismatch between early life programming and subsequent environmental conditions are considered. We review the role of maternal stress, egg conditions, incubation settings (temperature, light, sound, odour) and chick brooding conditions on behavioural programming that could be linked to IP. Brain and behavioural development can be programmed by prenatal and postnatal environmental conditions, which if suboptimal could lead to a tendency to develop IP later in life, as we illustrate with a Jenga tower that could fall over if not built solidly. If so, steps taken to optimise the environmental conditions of previous generations and incubation conditions, reduce stress around hatching, and guide the early learning of chicks will aid in prevention of IP in commercial laying hen flocks.

Current methods and techniques of beak trimming laying hens, welfare issues and alternative approaches

Beak trimming is used in the egg industry to prevent mortality from cannibalism and minimise injurious pecking, vent pecking, aggressive pecking at the head and all forms of feather pecking, although the practice does not completely reduce the damage. There are alternatives to beak trimming, but they have not been reliable in preventing injurious pecking. However, beak trimming should not be used without providing birds enriched indoor and outdoor environments. Even when birds are beak trimmed, providing enriched facilities is recommended. The two main methods of beak trimming are hot blade (HB) and infrared beak treatment (IRBT). HB trimming removes the beak tips and cauterises the beak stump. The IRBT method uses heat from an infrared lamp to treat the outer beak and the underlying tissue. Initially, the tips of the beak remain intact and then soften and wear as the bird uses its beak. In contrast, the HB method results in an open wound that takes 3 weeks to heal. Two major welfare issues arise from beak trimming. The first is loss of sensory input because of removal of or heat treatment of sensory receptors in the beak. The second issue is the potential for acute and chronic pain from severing or heat treatment of nerves. HB trimming initially results in acute pain but there is limited evidence for beak sensitivity in IRBT birds. The development of neuromas in the beak have been implicated as a cause of chronic pain after HB trimming. When birds are HB trimmed (one-half of upper beak; one-third of lower) in the first 10 days of life, neuromas will develop, but they will resolve, compared with birds trimmed at older ages. However, neuromas will not resolve in 10-day old birds if more than one-half of the beak is HB trimmed. While HB trimming is performed according to accreditation standards by removal of one-half the upper beak and one-third of the lower beak is considered excessive, it prevents beak regrowth and the need to subject birds to re-trimming and a second bout of acute pain from the beak wound. Current levels of IRBT to treat half of the beak using the vendors quality-assurance protocol have been implemented worldwide to ensure that neuroma formation is prevented; however, if severe levels of IRBT are used, acute pain and subsequent neuromas may persist. The main impact of beak trimming is how the bird uses its beak when it eats, drinks and pecks at other birds and the environment. Reduced feed intake after HB trimming indicates pain associated with pecking or difficulty in eating. HB-trimmed birds initially show an increase in listlessness and guarding behaviours and increased inactivity, which indicates pain. IRBT and HB-trimmed birds have fewer aggressive pecks at the head, and there is a reduction in severe feather pecking and better feather scores, which results in a large reduction in mortality. Depending on the severity of IRBT and HB trimming, the advantage of using IRBT is improved welfare.

Cardiovascular tolerance of intravenous bupivacaine in broiler chickens (Gallus gallus domesticus) anesthetized with isoflurane

OBJECTIVE

To determine the median effective dose (ED₅₀) of intravenous (IV) bupivacaine associated with a 50% probability of causing clinically relevant cardiovascular effects [defined as 30% change in heart rate (HR) or mean arterial pressure (MAP)] in chickens anesthetized with isoflurane.

STUDY DESIGN

Randomized up-and-down study.

ANIMALS

A total of 14 Ross-708 broiler chickens (Gallus gallus domesticus) weighing 1.70-2.75 kg.

METHODS

Anesthesia was induced and maintained with isoflurane. Monitoring included the electrocardiogram and invasive arterial pressures. Chickens were administered bupivacaine IV over 2 minutes using a dose based on the response of the previous animal. Dose was decreased when HR and/or MAP in the previous animal increased or decreased ≥30% after bupivacaine administration, or increased when HR or MAP changed <30%. The ED₅₀ was defined as the dose resulting in ≥30% variation in HR or MAP in 50% of the population studied.

RESULTS

The IV ED₅₀ of bupivacaine was 1.94 mg kg^-1 using Dixon's up-and-down method and 1.96 mg kg^-1 by logistic regression.

CONCLUSIONS AND CLINICAL RELEVANCE

These results suggest that 1.33 and 1.96 mg kg^-1 of IV bupivacaine are associated with a respective 1 or 50% probability of a clinically significant change in MAP in isoflurane-anesthetized chickens. Identification of the cardiovascular changes associated with different doses of bupivacaine can be used as the basis for studies of therapeutic applications in the domestic chicken. Further studies are required to determine interspecies variation.

Review of rearing-related factors affecting the welfare of laying hens

Laying hens may face a number of welfare problems including: acute and chronic pain caused by beak trimming; exaggerated fearfulness that may cause stress and suffocation; difficulties in locating resources, resulting potentially in emaciation and dehydration; frustration and boredom, caused by an environment that is barren; feather pecking; cannibalism; foot lesions; and bone fractures. In Europe, a greater proportion of laying hens are housed in non-cage systems compared to the rest of the world. The extent of the different welfare problems may therefore vary between countries as the type of housing system influences the risk of suffering. More generally, many of these welfare problems are influenced by the rearing environment of the pullets. This article therefore focuses on welfare problems in laying hens that can be traced back to rearing. Factors that have been studied in relation to their effects on bird welfare include beak trimming, housing type, furnishing, enrichment, feeding, stocking density, flock size, sound and light levels, concentration of gasses, age at transfer from rearing to production facilities, similarity between rearing and production facilities, competence of staff, and interactions between bird strain and environment. The present review aims to summarize rearing-related risk factors of poor welfare in adult laying hens housed according to European Union legislation. It aims to identify gaps in current knowledge, and suggests strategies for improving bird welfare by improving rearing conditions. Two main conclusions of this work are that attempts should be made to use appropriate genetic material and that beak trimming should be limited where possible. In addition to this, the rearing system should provide constant access to appropriate substrates, perches, and mashed feed, and should be as similar as possible to the housing system used for the adult birds. Finally, young birds (pullets) should be moved to the production facilities before 16 weeks of age. The measures outlined in this review may be useful for improving the welfare of pullets and adult laying hens.

Avian analgesia

Avian analgesia is now recognized as a critical component of avian medicine and surgery. The need to recognize pain and to provide pain relief is the first step, and many anecdotal therapeutic doses have been extrapolated from other companion animals. Several published research investigations, using several species of birds, have begun to provide avian analgesia therapeutic information for clinical application. The challenge is to continue pushing this research forward with appreciation that there are approximately 10,000 known species of birds, perhaps 200 species commonly kept as pets, and that each species has a range of behaviors as varied as their species-specific PKs and PDs to each analgesic drug.

Diclofenac-induced biochemical and histopathological changes in white leghorn birds (Gallus domesticus)

OBJECTIVE

OBJECTIVE

To evaluate diclofenac-induced biochemical and histopathological changes in White Leghorn birds.

MATERIALS AND METHODS

Six-week-old birds were equally divided into three groups of six birds each. Group I served as control and received vehicle orally. The birds of Group II and III were orally administered with a single low (2 mg/kg) and high dose (20 mg/kg) of diclofenac sodium, respectively, and were observed for 7 days. The acute toxicity was assessed by observing the clinical signs and symptoms, mortality, alterations in blood biochemistry, and necropsy findings.

RESULTS

The birds of Group II showed only mild symptoms of diarrhea. In Group III, 50% of birds died in between 24 and 36 h post-treatment showing the symptoms of segregatory behavior, lethargy, terminal anorexia, and severe bloody diarrhea. The birds of Group II and the surviving birds of Group III showed a significantly (P<0.05) increased plasma uric acid, creatinine and plasma glutamic pyruvic transaminase (PGPT), and decreased total protein and albumin at 12 and 24 h post-treatment which returned to the normal levels at 36 h post-treatment. The dead birds of the high-dose group also showed similar pattern of biochemical changes at 12 and 24 h post-treatment and revealed extensive visceral gout with characteristic histopathological lesions in liver, kidney, heart, spleen, and intestine on post-mortem.

CONCLUSION

The results indicate that diclofenac sodium has hepatotoxic, nephrotoxic, and visceral gout inducing potentials in White Leghorn birds, especially at higher dose.

Assessment of the analgesic effects of ketoprofen in ducks anesthetized with isoflurane

OBJECTIVE

To determine whether administration of ketoprofen would have analgesic effects in spontaneously breathing ducks anesthetized with isoflurane.

ANIMALS

13 healthy adult wild-strain Mallard ducks.

PROCEDURE

Each duck was anesthetized twice in a crossover study design with 6 days between randomized treatments. Ducks were given ketoprofen (5 mg/kg, IM) or saline (0.9% NaCl) solution after a constant plane of anesthesia was established. Analgesia was assessed by measuring heart and respiratory rates and duration of application of a noxious stimulus. The noxious stimulus was applied 30, 50, and 70 minutes after drug administration and was maintained until gross purposeful movements were seen or for a maximum of 5 seconds.

RESULTS

At all 3 evaluation times, heart rate increases in response to the noxious stimulus were greater when ducks were given saline solution than when they were given ketoprofen. The increase in respiratory rate in response to the noxious stimulus was greater when ducks were given saline solution than when they were given ketoprofen only 70 minutes after drug administration. When ducks were given ketoprofen, duration of the noxious stimulus was significantly longer 50 and 70 minutes, but not 30 minutes, after drug administration.

CONCLUSIONS AND CLINICAL RELEVANCE

Ketoprofen reduced the increases in heart and respiratory rates associated with application of a noxious stimulus in spontaneously breathing adult Mallard ducks anesthetized with isoflurane delivered at approximately 2.9%, suggesting that ketoprofen had analgesic effects in these ducks. The onset of analgesic effects may be longer than 30 minutes in some ducks.

Assessing Pain in Animals

Assessing the experience of pain in animals is a difficult task, yet one that is important in animal welfare research. Some approaches to pain assessment in animals are reviewed here. General qualities of pain scales and specific parameters suitable for clinical and experimental pain assessments are discussed. It is argued that pain assessment will progress through an integration of objective and subjective observations of behaviour coupled with multiple measures in various other areas. Such multidimensional pain scales allow an adequate characterisation of the complexity of an individual animal's pain experience to be made. This knowledge improves the recognition and treatment of pain and will allow informed moral debate on the acceptability of practices such as castration and tail-docking of lambs.

Avian analgesia

Understanding behavioral indicators of pain and other assessment techniques can help one to recognize pain in birds and prompt us to treat birds with analgesics. An analgesic plan needs to include several modalities to help reduce pain in the avian patient. Analgesic therapy should be directed at treating the disease/injury in the periphery, and the changes that occur in the central nervous system (CNS). Both opioid and nonsteroidal anti-inflammatory drug (NSAID) therapeutics can be selected to provide analgesia for the avian patient.

Determination of the ED50 of isoflurane and evaluation of the isoflurane-sparing effect of butorphanol in cockatoos (Cacatua spp.)

The use of butorphanol as an analgesic in a psittacine species was evaluated by determining its isoflurane-sparing effects. The Effective Dose 50 (ED50) of isoflurane was determined using a bracketing technique based on the purposeful movement elicited by pressure applied to a digit with a hemostat. The ED50 of isoflurane for 11 cockatoos (four greater sulfur crested, three lesser sulfur crested, and four citron crested) was determined to be 1.44 +/- 0.07%. After the administration of 1 mg/kg of butorphanol tartrate intramuscularly (IM), the ED50 was significantly (P < .05) decreased to 1.08 +/- 0.05%. Physiological variables that changed significantly included decreases in heart rate, tidal volume (Vt), inspiratory (Ti) and expiratory times (Te), and an increase in respiratory rate. No complications resulted because of these changes. Based on the results, butorphanol produces an isoflurane-sparing effect in cockatoos and has the potential to be a useful analgesic in psittacines.