Thermal nociception as a measure of non-steroidal anti-inflammatory drug effectiveness in broiler chickens with articular pain

Biomechanics of landing in injured and uninjured chickens and the role of meloxicam

Birds use their legs and wings when transitioning from aerial to ground locomotion during landing. To improve our understanding of the effects of footpad dermatitis (FPD) and keel bone fracture (KBF) upon landing biomechanics in laying hens, we measured ground-reaction forces generated by hens (n = 37) as they landed on force plates (Bertec Corporation, Columbus, OH) from a 30 cm drop or 170 cm jump in a single-blinded placebo-controlled trial using a cross-over design where birds received an anti-inflammatory (meloxicam, 5 mg/kg body mass) or placebo treatment beforehand. We used generalized linear mixed models to test for effects of health status, treatment and their interaction on landing velocity (m/s), maximum resultant force (N), and impulse (force integrated with respect to time [N s]). Birds with FPD and KBF tended to show divergent alterations to their landing biomechanics when landing from a 30 cm drop, with a higher landing velocity and maximum force in KBF compared to FPD birds, potentially indicative of efforts to either reduce the use of their wings or impacts on inflamed footpads. In contrast, at 170 cm jumps fewer differences between birds of different health statuses were observed likely due to laying hens being poor flyers already at their maximum power output. Our results indicate that orthopedic injuries, apart from being welfare issues on their own, may have subtle influences on bird mobility through altered landing biomechanics that should be considered.

Bone Metabolite Profile Differs between Normal and Femur Head Necrosis (FHN/BCO)-Affected Broilers: Implications for Dysregulated Metabolic Cascades in FHN Pathophysiology

Femur head necrosis (FHN), also known as bacterial chondronecrosis with osteomyelitis (BCO), has remained an animal welfare and production concern for modern broilers regardless of efforts to select against it in primary breeder flocks. Characterized by the bacterial infection of weak bone, FHN has been found in birds without clinical lameness and remains only detectable via necropsy. This presents an opportunity to utilize untargeted metabolomics to elucidate potential non-invasive biomarkers and key causative pathways involved in FHN pathology. The current study used ultra-performance liquid chromatography coupled with high-resolution mass spectrometry (UPLC-HRMS) and identified a total of 152 metabolites. Mean intensity differences at p < 0.05 were found in 44 metabolites, with 3 significantly down-regulated and 41 up-regulated in FHN-affected bone. Multivariate analysis and a partial least squares discriminant analysis (PLS-DA) scores plot showed the distinct clustering of metabolite profiles from FHN-affected vs. normal bone. Biologically related molecular networks were predicted using an ingenuity pathway analysis (IPA) knowledge base. Using a fold-change cut off of -1.5 and 1.5, top canonical pathways, networks, diseases, molecular functions, and upstream regulators were generated using the 44 differentially abundant metabolites. The results showed the metabolites NAD+, NADP+, and NADH to be downregulated, while 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR) and histamine were significantly increased in FHN. Ascorbate recycling and purine nucleotides degradation were the top canonical pathways, indicating the potential dysregulation of redox homeostasis and osteogenesis. Lipid metabolism and cellular growth and proliferation were some of the top molecular functions predicted based on the metabolite profile in FHN-affected bone. Network analysis showed significant overlap across metabolites and predicted upstream and downstream complexes, including AMP-activated protein kinase (AMPK), insulin, collagen type IV, mitochondrial complex, c-Jun N-terminal kinase (Jnk), extracellular signal-regulated kinase (ERK), and 3β-hydroxysteroid dehydrogenase (3β HSD). The qPCR analysis of relevant factors showed a significant decrease in AMPKα2 mRNA expression in FHN-affected bone, supporting the predicted downregulation found in the IPA network analysis. Taken as a whole, these results demonstrate a shift in energy production, bone homeostasis, and bone cell differentiation that is distinct in FHN-affected bone, with implications for how metabolites drive the pathology of FHN.

Pharmacokinetics of meloxicam in laying hens after single intravenous, oral, and intramuscular administration

The objective of this study was to determine the pharmacokinetics of meloxicam after a single intravenous (IV), intramuscular (IM), and oral (PO) dose at 1 mg/kg body weight in Jing Hong laying hens. Blood samples were collected at predetermined time points. Plasma meloxicam concentrations were determined using a validated high-performance liquid chromatography (HPLC) assay method and then subjected to a non-compartmental analysis. After IV administration, meloxicam had a mean (±SD) volume of distribution at steady-state (Vd_ss ) of 206.50 ± 25.23 ml/kg, a terminal half-life (t_1/2λ ) of 5.45 ± 0.53 h, and a total body clearance (Cl) of 26.48 ± 4.13 ml/h/kg. After PO and IM administration, meloxicam was absorbed relatively rapidly: the peak concentrations (C_max s) of 3.04 ± 0.56 and 8.94 ± 2.31 μg/ml were observed at 3.08 and 0.80 h, respectively. After PO and IM administration, the absolute bioavailability (F) was determined as 70.13% and 125.50%, respectively. Assuming that hens shared the same analgesic threshold of meloxicam (0.5 μg/ml) with humans, the plasma concentrations after three different routes (PO, IM, and IV) of administration were above this value for 16.7, 19.2, and 14.9 h, respectively.

Are changes in behavior of fast-growing broilers with slight gait impairment (GS0-2) related to pain?

Impaired walking ability in terms of slight or definite defects is more common in broiler production than lameness that obviously hinders movement, but it has received limited scientific attention. This study aimed to compare behavior of conventional broilers with impaired walking ability (assessed as gait score (GS) 2) with those walking normally (GS0) and those with only a slight gait defect (GS1). Behavior in the home environment was registered, and an analgesic intervention to quantify changes in time budgets indicating pain relief was applied. The study included 192 Ross 308 broilers. On day 27 of age, the birds were distributed as evenly as possible into birds of GS0 and GS2 of each sex based on obtained gait score. Following this, each experimental bird was housed with 3 companion birds. On days 30 and 32 of age, the behavior in the home pens was recorded. All experimental birds were injected with the NSAID carprofen on one of the 2 d and saline on the other. The statistical analyses used the GS scored on the day of recording as explanatory factor. Compared to GS0 birds, GS2 birds tended to be more inactive (mean (CI): 4,193 (3,971–4416) vs. 4,005 (3,753–4,257) s; P = 0.074), spent more time sitting while feeding (306 (266–353) vs. 213 (180–251) s; P = 0.026), were less likely to perch (probability: 0.78 (0.69–0.85) vs. 0.91 (0.85–0.95); P = 0.012), and spent less time performing comfort behavior (749 (689–814) s vs. 875 (792–967) s; P = 0.043). Compared to GS1 birds, GS2 birds spent more time inactive (GS1: 4,022 (3,818–4225) s; P = 0.027), less time foraging (289 (253–329) vs. 347 (309–388) s; P = 0.047), and were less likely to perch (GS1: 0.90 (0.86–0.93); P = 0.001). For some of these behavioral variables, administration of carprofen led to behavioral changes across the GSs, which may suggest that the behavioral expression of the broilers was limited by pain. These findings are of relevance to animal welfare, but the underlying causes are still not fully clarified.

Endowing polyetheretherketone with anti-inflammatory ability and improved osteogenic ability

Both osteogenesis and anti-inflammatory bioactive materials play a vital role in the regeneration of skeletal defects. Bone inflammation is hard to cure and can lead to malformation or amputation. The purpose of this study is to use anti-inflammatory drugs to endow polyetheretherketone (PEEK) with the dual ability to achieve anti-inflammatory effects while maintaining favorable biocompatibility. In this experiment, the porous PEEK was immersed in an aspirin (ASP) solution after sulfonation, and the obtained porous PEEK had significantly improved the anti-inflammatory abilities. Additionally, grafting the bone forming peptide (BFP) onto the porous PEEK can distinctly enchance the osteogenesis capability. The effects of the BFP polypeptide on the proliferation of MC3T3-E1 cells and ALP activity, and the effects of aspirin on inflammation were systematically investigated. The modified material showed favorable biocompatibility and osteogenic ability. The results suggest that the combination of the BFP polypeptide with aspirin may lead to a synergetic effect on the stimulation of osteogenesis and on the reduction of inflammation.

Bacillus subtilis-based probiotic promotes bone growth by inhibition of inflammation in broilers subjected to cyclic heating episodes

Heat stress as an environmental stressor causes abnormal bone remodeling and microarchitectural deterioration. The objective of this study was to investigate the effects of a Bacillus subtilis–based probiotic on bone mass of broilers subjected to cycling high ambient temperature. One hundred and twenty 1-day-old Ross 708 male broiler chicks were randomly assigned to 2 dietary treatments (12 pens per treatment): control diet and the control diet plus 250-ppm probiotic consisting of 3 strains of Bacillus subtilis. Room temperature was gradually decreased from 35°C on day 1 by 0.5°C/d until day 15, when ambient temperature was increased from 28°C to 32°C for 10 h (07:00 h–17:00 h) daily until day 44. Samples of blood, leg bones (tibia and femur), and brains (raphe nuclei and hypothalamus) were collected at day 43, while latency to lie test was conducted at day 44. Compared with controls, probiotic supplementation increased bone mineral content, weight, size, weight to length index, and reduced robusticity index in the tibia and femur (P < 0.05) of broilers subjected to heat stress. Serum concentrations of c-terminal telopeptide of type I collagen (CTX) were reduced (P = 0.02) by the probiotic supplementation, while ionized calcium, phosphate, and osteocalcin were not affected (P > 0.05). Moreover, tumor necrosis factor-α (TNF-α) in probiotic fed broilers was decreased (P = 0.003) without changes of plasma interleukin (IL)-6, IL-10, interferon-γ, and corticosterone concentrations. There were no treatment effects on the concentrations of peripheral serotonin and central serotonin and catecholamines (norepinephrine, epinephrine, and dopamine) as well as their metabolites. These results may indicate that dietary supplementation of Bacillus subtilis–based probiotic increases bone growth in broilers under a cyclic heating episode probably via inhibition of bone resorption, resulting from downregulation of the circulating TNF-α and CTX. Dietary probiotic supplementation may be a management strategy for increasing skeletal health of broilers under hot weather.

Analgesic Efficacy of Tramadol Compared With Meloxicam in Ducks (Cairina moschata domestica) Evaluated by Ground-Reactive Forces

The purpose of this study was to determine the efficacy of tramadol and meloxicam in an induced, temporary arthritis model in ducks as assessed by ground-reactive forces measured by a pressure-sensitive walkway (PSW) system. Twelve ducks (Cairina moschata domestica) were randomly separated into 3 equal groups of 4 birds each: water control, tramadol treatment, and meloxicam treatment. Baseline measurements were collected by having all ducks walk along a 3-m-long PSW in a custom-built corral before anesthesia and induction of arthritis. Arthritis was induced in all groups through injection, under anesthesia, of a 3% monosodium urate (MSU) solution into the intertarsal joint. One hour after MSU injection, birds were orally gavage fed 1 mL of tap water (control), tramadol (30 mg/kg), or meloxicam (1 mg/kg). After treatments, all ducks were reevaluated on the PSW at 1, 2, 3, 4, 8, and 24 hours post-MSU injection. The difference in maximum force was significantly greater in the control group than in both the tramadol- (P = .006) and meloxicam-treated (P = .03) individuals. Post hoc comparisons revealed differences between control and treated birds occurred only at the 3- and 4-hour time points after administration. No differences were found in the absolute difference in maximum force between tramadol- and meloxicam-treated birds at any time point (P > .05). Results of this study support the hypothesis that tramadol (30 mg/kg PO) and meloxicam (1 mg/kg PO) improve certain objective variables in an induced arthritis model in ducks. Our findings also support studies in other avian species that determined that both tramadol and meloxicam are effective analgesic drugs in some birds.

Effects of noxious stimuli on the electroencephalogram of anaesthetised chickens (Gallus gallus domesticus)

The reliable assessment and management of avian pain is important in the context of animal welfare. Overtly expressed signs of pain vary substantially between and within species, strains and individuals, limiting the use of behaviour in pain studies. Similarly, physiological indices of pain can also vary and may be confounded by influence from non-painful stimuli. In mammals, changes in the frequency spectrum of the electroencephalogram (EEG) recorded under light anaesthesia (the minimal anaesthesia model; MAM) have been shown to reliably indicate cerebral responses to noxious stimuli in a range of species. The aim of the current study was to determine whether the MAM can be applied to the study of nociception in birds. Ten chickens were lightly anaesthetised with halothane and their EEG recorded using surface electrodes during the application of supramaximal mechanical, thermal and electrical noxious stimuli. Spectral analysis revealed no EEG responses to any of these stimuli. Given that birds possess the neural apparatus to detect and process pain, and that the applied noxious stimuli elicit behavioural signs of pain in conscious chickens, this lack of response probably relates to methodological limitations. Anatomical differences between the avian and mammalian brains, along with a paucity of knowledge regarding specific sites of pain processing in the avian brain, could mean that EEG recorded from the head surface is insensitive to changes in neural activity in the pain processing regions of the avian brain. Future investigations should examine alternative electrode placement sites, based on avian homologues of the mammalian brain regions involved in pain processing.

Thermal nociceptive threshold testing detects altered sensory processing in broiler chickens with spontaneous lameness

Lameness is common in commercially reared broiler chickens but relationships between lameness and pain (and thus bird welfare) have proved complex, partly because lameness is often partially confounded with factors such as bodyweight, sex and pathology. Thermal nociceptive threshold (TNT) testing explores the neural processing of noxious stimuli, and so can contribute to our understanding of pain. Using an acute model of experimentally induced articular pain, we recently demonstrated that TNT was reduced in lame broiler chickens, and was subsequently attenuated by administration of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs). This study extended these findings to a large sample of commercial broilers. It examined factors affecting thermal threshold (Part 1) and the effect of an NSAID drug (meloxicam, 5 mg/kg) and of an opioid (butorphanol; 4 mg/kg) (Part 2). Spontaneously lame and matched non-lame birds (n=167) from commercial farms were exposed to ramped thermal stimulations via a probe attached to the lateral aspect of the tarsometatarsus. Baseline skin temperature and temperature at which a behavioural avoidance response occurred (threshold) were recorded. In Part 1 bird characteristics influencing threshold were modelled; In Part 2 the effect of subcutaneous administration of meloxicam or butorphanol was investigated. Unexpectedly, after accounting for other influences, lameness increased threshold significantly (Part 1). In Part 2, meloxicam affected threshold differentially: it increased further in lame birds and decreased in non-lame birds. No effect of butorphanol was detected. Baseline skin temperature was also consistently a significant predictor of threshold. Overall, lameness significantly influenced threshold after other bird characteristics were taken into account. This, and a differential effect of meloxicam on lame birds, suggests that nociceptive processing may be altered in lame birds, though mechanisms for this require further investigation.

The effects of two non-steroidal anti-inflammatory drugs on the mobility of laying hens with keel bone fractures

OBJECTIVE

Investigate the effects of administration of meloxicam and carprofen on the mobility of hens with and without keel fractures.

STUDY DESIGN

Within each of two experiments a 'blinded' randomised cross over design whereby birds received either the test drug (carprofen or meloxicam) or saline.

ANIMALS

Two groups of Lohman Brown hens with and without keel bone fractures.

METHODS

The first group (n = 63) was treated with carprofen 25 mg kg(-1) and saline subcutaneously, twice. The second group (n = 40) was treated with meloxicam (5 mg kg(-1) ) and saline subcutaneously. The latency of birds to fly down from perches 50, 100 and 150 cm above the ground was measured after each treatment. Data from experiment 1 and 2 were analysed separately; the effects of drug treatment compared with saline on landing time for birds with and without keel bone fractures were evaluated using MLwiN.

RESULTS

In both experiments latency to fly down from perches was longer in hens with keel fractures and there was a significant interaction between perch height and fracture status. For carprofen, at the 50 cm, 100 cm and 150 cm perch heights, birds with fractures took (mean ± SD) 2.5 ± 2.9, 6.8 ± 9.7 and 11.5 ± 13.2 seconds respectively to fly down compared with 1.3 ± 0.5, 2.3 ± 1.2 and 4.2 ± 3.1 seconds for birds without fractures. For meloxicam, at the 50 cm, 100 cm and 150 cm perch heights, birds with fractures took 2.9 ± 2.5, 49.8 ± 85.4 and 100.3 ± 123.6 seconds respectively compared with 0.7 ± 0.5, 2.5 ± 7.1 and 3.0 ± 4.6 seconds to fly down for birds without fractures. There was no significant effect of carprofen or meloxicam treatment.

CONCLUSION AND CLINICAL RELEVANCE

These data provide further confirmation that keel fractures reduce the willingness of birds to move from perches.