Effects of free-range and confined housing on joint health in a herd of fattening pigs

The epidemiology of osteochondrosis in an insured Swedish dog population

Osteochondrosis (OC) is a focal disturbance of endochondral ossification due to a failure of blood supply to the epiphyseal growth cartilage. In dogs, OC most commonly affects the shoulder joint, followed by the elbow, tarsal, and stifle joints. The condition is associated with clinical signs such as lameness and pain and the prognosis varies depending on the affected joint. Most epidemiologic studies of OC in dogs were performed over 20 years ago, and updated estimates of disease incidence are lacking. Therefore, the objectives of this study were to provide population-based estimates of the incidence rate, cause-specific mortality rate, and age at diagnosis of appendicular OC (AOC, including OC of the shoulder, elbow, stifle, and tarsal joints) and stifle and tarsal OC separately, using data from Agria Djurförsäkring in Sweden (2011-2016). Further, the study aimed to evaluate the risk of OC in subgroups divided by breed and sex and describe previous, concurrent, and subsequent diagnoses of the affected joint in dogs with stifle or tarsal joint OC. The study population included just over 600,000 dogs, of which 685 were affected by AOC. Stifle joint OC (n = 113) was more common than tarsal joint OC (n = 80). The incidence rate of AOC was 3.77 (95% confidence interval (CI): 3.49-4.07) cases per 10,000 dog-years at risk, while the incidence rate of stifle and joint tarsal OC was 0.64 (95% CI: 0.53-0.77) and 0.43 (95% CI: 0.34-0.54) cases per 10,000 dog-years at risk, respectively. All breeds at increased risk of AOC were large or giant, and male dogs had an increased risk of AOC compared to female dogs (RR 1.76, 95% CI: 1.50-2.07, p < 0.001). The median age at first diagnosis during the study period was 0.74 (0.32-11.5) years for AOC, 2.62 (0.45-8.82) years for stifle joint OC, and 0.73 (0.35-7.35) years for tarsal joint OC. Of the dogs with stifle or tarsal joint OC, 30.2% and 15.0% had a previous diagnosis of stifle/tarsal joint pain or other unspecific clinical signs, respectively, and 13.8% of the dogs with stifle joint OC suffered subsequent cruciate ligament rupture. Osteochondrosis was the most common reason for euthanasia in the affected dogs. In total, 77 dogs were euthanised due to AOC during the study period.

Finding Predictors of Leg Defects in Pigs Using CNV-GWAS

One of the most important areas of modern genome research is the search for meaningful relationships between genetic variants and phenotypes. In the livestock field, there has been research demonstrating the influence of copy number variants (CNVs) on phenotypic variation. Despite the wide range in the number and size of detected CNVs, a significant proportion differ between breeds and their functional effects are underestimated in the pig industry. In this work, we focused on the problem of leg defects in pigs (lumps/growths in the area of the hock joint on the hind legs) and focused on searching for molecular genetic predictors associated with this trait for the selection of breeding stock. The study was conducted on Large White pigs using three CNV calling tools (PennCNV, QuantiSNP and R-GADA) and the CNVRanger association analysis tool (CNV-GWAS). As a result, the analysis identified three candidate CNVRs associated with the formation of limb defects. Subsequent functional analysis suggested that all identified CNVs may act as potential predictors of the hock joint phenotype of pigs. It should be noted that the results obtained indicate that all significant regions are localized in genes (CTH, SRSF11, MAN1A1 and LPIN1) responsible for the metabolism of amino acids, fatty acids, glycerolipids and glycerophospholipids, thereby related to the immune response, liver functions, content intramuscular fat and animal fatness. These results are consistent with previously published studies, according to which a predisposition to the formation of leg defects can be realized through genetic variants associated with the functions of the liver, kidneys and hematological characteristics.

Ante-mortem and Post-mortem Inspection and Relationship between Findings in a North Albanian Pig Slaughterhouse

In June 2014, Albania was granted EU candidate status, thus starting a process of compliance with the membership criteria. In this context, a modern meat inspection approach in line with the European legislation was applied to a pig slaughterhouse in northern Albania in order to investigate the ante-mortem (AM) and post-mortem (PM) conditions and the relationship between these findings. For this purpose, 3930 pigs divided into 35 batches were evaluated over a 3-month period. The most frequent AM conditions recorded were tail lesions and dyspnea (9.1%), followed by skin (8.9%) and ear lesions (8.5%), while in the PM inspections, pleuritis was the most frequently observed condition (10.2%), followed by pneumonia (8.5%), liver alterations (5.7%), milk spot liver (3.8%), and pericarditis (3.3%). With the exception of liver alterations, the other PM lesions mentioned were positively associated with lesions on the ears (OR = 1.036; p < 0.001) and skin (OR = 1.026; p = 0.011) and dyspnea (OR = 1.021; p = 0.005), confirming the link between these variables and the health and welfare conditions of pigs on farms. Overall, the evidence that emerged from this Albanian slaughterhouse can be considered in line with other European contexts, especially in light of the considerable variability in the data present in the literature.

A method for labelling lesions for machine learning and some new observations on osteochondrosis in computed tomographic scans of four pig joints

Background

Osteochondrosis is a major cause of leg weakness in pigs. Selection against osteochondrosis is currently based on manual scoring of computed tomographic (CT) scans for the presence of osteochondrosis manifesta lesions. It would be advantageous if osteochondrosis could be diagnosed automatically, through artificial intelligence methods using machine learning. The aim of this study was to describe a method for labelling articular osteochondrosis lesions in CT scans of four pig joints to guide development of future machine learning algorithms, and to report new observations made during the labelling process. The shoulder, elbow, stifle and hock joints were evaluated in CT scans of 201 pigs.

Results

Six thousand two hundred fifty osteochondrosis manifesta and cyst-like lesions were labelled in 201 pigs representing a total volume of 211,721.83 mm³. The per-joint prevalence of osteochondrosis ranged from 64.7% in the hock to 100% in the stifle joint. The lowest number of lesions was found in the hock joint at 208 lesions, and the highest number of lesions was found in the stifle joint at 4306 lesions. The mean volume per lesion ranged from 26.21 mm³ in the shoulder to 42.06 mm³ in the elbow joint. Pigs with the highest number of lesions had small lesions, whereas pigs with few lesions frequently had large lesions, that have the potential to become clinically significant. In the stifle joint, lesion number had a moderate negative correlation with mean lesion volume at r = − 0.54, p < 0.001.

Conclusions

The described labelling method is an important step towards developing a machine learning algorithm that will enable automated diagnosis of osteochondrosis manifesta and cyst-like lesions. Both lesion number and volume should be considered during breeding selection. The apparent inverse relationship between lesion number and volume warrants further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03426-x.

Gross, histopathologic, microbiologic, and radiologic characterization of lesions associated with clinical lameness in a cohort of group-housed sows euthanized for lameness

Lameness in sows is reported as the most frequent cause of early culling from commercial farms and results in reduced productivity, economic losses, and a negative impact on animal welfare. Osteochondrosis was reported as the leading cause of lameness in North American sows and, although more recent European studies report infectious arthritis as the leading cause, lameness in US production facilities using group housing for gestating sows has not yet been evaluated. This study's aim was to characterize lesions associated with lameness in the appendicular musculoskeletal system of 26 sows euthanized for lameness using pathologic, radiologic, and microbiologic analyses. Of 178 total lesions, infectious lesions were most common (54%), predominated in distal limb segments (ie, at or distal to carpi and tarsi) and more often correlated with the clinically lame limb, whereas osteochondrosis and degenerative osteoarthritis predominated in proximal limb segments (ie, at or proximal to cubital and stifle joints) and rarely correlated with the clinically lame limb. The location and characteristics of infectious lesions, including mixed bacterial growth isolated from 22/22 orthopedic sites representing 19 sows with Trueperella pyogenes isolated in 16/22 (73%) of samples, suggest an etiologic component involving trauma. Radiography had a 70.6% sensitivity and 93.9% specificity for detecting infectious lesions affecting tarsocrural, antebrachiocarpal, and digital (ie, claw) regions combined. The frequency, type, and location of infectious lesions identified in this cohort of sows euthanized for lameness differ from previous reports, indicating the need for further investigation of the etiopathogenesis, earlier detection methods, and prevention.

How Housing Conditions Determine the Welfare of Pigs

Humans who care for pigs prefer an environment that not only allows the pigs to express their natural behaviors but also limits the development of aggression and stereotypes. Most of the behavioral and health problems encountered by pigs in barren, conventional conditions are solved by alternative housing systems. However, it is not known whether these systems are advantageous in terms of the performance of pigs. In this work, we review the effects of housing systems on pigs' behaviors and performance, which are among the major indicators of the welfare of these animals. Research results point out that outdoor systems are more ideal for sows and fatteners than buildings. Nonetheless, outdoor housing is associated with two major effects in both groups: increased activity due to environmental exploration and higher space allowance, and increased incidence of injuries compared to indoor systems. Sows are more active when housed in groups, but they experience an increased frequency of injuries. According to the literature, group-housed sows give birth to healthy piglets with good daily weight gains. The difference in the fattening and slaughter performance of pigs raised indoors vs. outdoors remains unclear, and the results reported so far are inconsistent. Outdoor systems seem to be associated with a higher incidence of osteochondrosis and lesions of elbow and hock joints, whereas indoor systems cause a greater degree of body soiling in pigs. Based on the reviewed literature, it may be concluded that outdoor housing helps to solve behavioral issues in pigs but leads to other problems in pig production.

Comparison of 12 Different Animal Welfare Labeling Schemes in the Pig Sector

Simple Summary

Welfare requirements from an animal point of view are the same regardless of the country. However, differing requirements of animal welfare schemes make it hard for consumers to make informed choices. Therefore, an open and coherent labeling scheme that provides information on farm animal welfare will be beneficial from the consumer perspective. We reviewed 12 pig welfare schemes. We aimed to identify consistencies and differences in welfare requirements between these schemes. The studied welfare requirements were heterogeneous in the potential each scheme had to advance pig welfare. Certain requirements barely exceeded the minimum standards for the protection of pigs in European Union (EU) legislation, but the more demanding tiers of multitier schemes had the potential to enhance animal welfare. The most ambitious tiers could improve animal welfare substantially and, in terms of resources available to the animal, they often were convergent with organic animal farming standards. Because of variation of welfare requirements between the labels, it was challenging to compare existing labeling schemes. Adopting a harmonized labeling terminology and standard, increased use of animal-based measures, and open communication will make labeling more reliable and transparent, which will contribute to the availability of standardized animal-friendly products and will be equitable from an animal welfare perspective.

Abstract

Animal welfare labeling schemes have been developed to respond to consumers’ expectations regarding farm animal welfare. They are designed to certify that labeled products comply with certain animal welfare standards. In this study, 12 pig welfare labeling schemes were reviewed, and their criteria related to pig welfare were compared. Information regarding farrowing criteria, space allowance, outdoor access, mutilations, and provision of enrichments and bedding material were gathered from the labels’ internet pages and documentation. The results indicated a substantial variation between the labels in terms of the level of animal welfare they ensure. While certain schemes barely exceeded the minimum standards for the protection of pigs in the European Union, more demanding tiers of the multitier schemes had the potential to improve animal welfare substantially. The most ambitious tiers of multistage schemes were often comparable to organic standards providing outdoor facilities and additional space. The heterogeneity of the labels’ standards complicates the comparison of labels.

Health and welfare in organic livestock production systems—a systematic mapping of current knowledge

This review aimed to systematically map and summarize the status of animal health and welfare in organic production. The prevalence of diseases and behavioural effects in organic dairy cow, beef cattle, sheep, pig, laying hen and broiler chicken were discussed in the context of the organic values and current knowledge on animal health and welfare. In total 166 peer-reviewed scientific publications between 2008 and 2020 were included. No strong evidence for neither inferior nor distinctly higher animal welfare in organic compared with conventional production could be supported. The welfare status of organic livestock is in general good in relation to the OIE definition of animal health and welfare. However, organic systems are still facing several challenges related to animal health and the arising of goal conflicts due to management and practical implications. Greater possibilities to perform species-specific behaviours in organic production systems, however, indicate that the organic standards offer a good framework for high animal welfare management. For organic dairy farmers, the main health problems are similar to those of non-organic farms; especially mastitis and lameness need improvement. Parasites, together with mastitis and lamb mortality, are important welfare issues in organic sheep production. Piglet mortality, leg problems, parasite load and increasing respiratory problems are of major relevance in organic pig production. For organic laying hens, major health challenges relate to feather pecking and cannibalism, parasites and possibilities to express species-specific behaviours. For organic broilers, dermatitis of footpads, hocks and breast are reported as main health issues.

Biomechanical loading of the porcine femorotibial joint during maximal movements: An exploratory, ex vivo study

Thus far, there is a lack of scientific investigation regarding the hypothesis that biomechanical factors contribute to the cross-species pathogenesis of osteochondrosis (OC). Therefore, the aim of this pilot study was to investigate whether high (peak) pressures occur in the porcine femorotibial (FT) joint. In this experimental, ex vivo study, the right hind limbs of seven weaned piglets were subjected to maximal joint excursions, as a priori radiologically estimated. Subsequently, the intra-articular pressures were measured using sensors placed in both the medial and the lateral compartments of the FT joint. The overall highest individual peak pressure was found in the lateral FT joint during maximal extension (2611 kPa; group mean ± standard deviation (SD) 982.3 ± 988.2 kPa). In the medial FT joint, the highest individual peak pressure was found during maximal adduction (1481 kPa; group mean ± SD 664.9 ± 393.2 kPa). Moreover, nearly 30% of the ex vivo peak pressures were above published thresholds for cartilage catabolism (>500 kPa/0.5 MPa), but not for interfering with cell viability (>5 MPa). In conclusion, this ex vivo study on FT joint pressures in weaned piglets showed that FT joint movements at maximal excursions are related to concomitant internal peak joint pressures. More studies should be performed to evaluate the possible biomechanical relation of these observations with osteochondrosis, which would allow the design of preventive measures in the pig industry, to avoid extreme limb movements and concomitant joint peak pressures in vivo.

Effects of supplementing organic microminerals and methionine with or without limiting growth during the rearing phase of replacement gilts on lameness, growth, and body composition

Previous research suggested that lameness in growing pigs could be reduced using feeding strategies, such as limiting growth rate and supplementing trace minerals (TM) and (or) methionine (Met). The present study evaluates effects of 1) TM and Met and 2) limiting total lysine (Lys) during the rearing phase (90 d) of gilts (as a means to limit growth rate) on lameness, performance, and sow claw health and productivity (to first parity). Gilts (n = 240; 58.0 ± 11.1 kg body weight [BW]) were blocked, distributed into pens of 10 gilts, and pens were allocated to a 2 × 2 factorial arrangement. Factors were: 1) control or TM plus Met, which provided additional 10, 20, and 50 mg/kg of chelated copper, manganese, and zinc, respectively (0.1%, Aplomotec Plus, Tecnología & Vitaminas, S.L.; Alforja, Spain), and a 1.01 Met:Lys ratio and 2) standard Lys was formulated to meet growth requirements or low Lys to 19% below growth requirements. Feeding was provided through two phases, first between 119 and 163 d of age (phase I) and the second between 163 and 209 d of age (phase II). Diets had 2.43 and 2.31 Mcal net energy/kg for phases I and II, respectively, and were offered ad libitum. Low Lys did not affect feed intake but rather reduced average daily gain (ADG) by 6.35% and the final BW by 3.80% compared with standard Lys (P < 0.001). Low Lys reduced ADG (P < 0.001) and gain:feed (P = 0.012) during phase I but not during phase II. Lameness prevalence was 7.92% during rearing and increased with time (P < 0.001). Final BW (151 kg) and ADG (989 g) were similar (P > 0.05) whether gilts displayed lameness or not. Lameness was low in severity and not affected by dietary factors. However, TM- plus Met-fed gilts were 19.2 kg heavier (P = 0.016) than were control at lameness detection. On the sow farm, there was no evidence for differences in lameness or claw lesions among previous dietary treatments. In conclusion, lameness prevalence during the rearing phase was similar, independent of TM plus Met supplement, low Lys, or the interaction. Insufficient reduction of ADG and low severity in lameness may have limited the potential of dietary treatments. Moreover, a greater deficiency of Lys would be needed to achieve the degree of growth reduction previously reported to lessen lameness through feed restriction.

Cartilage canals in the distal intermediate ridge of the tibia of fetuses and foals are surrounded by different types of collagen

Some epiphyseal growth cartilage canals are surrounded by a ring of hypereosinophilic matrix consisting of collagen type I. Absence of the collagen type I ring may predispose canal vessels to failure and osteochondrosis, which can lead to fragments in joints (osteochondrosis dissecans). It is not known whether the ring develops in response to programming or biomechanical force. The distribution that may reveal the function of the ring has only been described in the distal femur of a limited number of foals. It is also not known which cells are responsible for producing the collagen ring. The aims of the current study were to examine fetuses and foals to infer whether the ring forms in response to biomechanical force or programming, to describe distribution and to investigate which cell type produces the ring. The material consisted of 46 fetuses and foals from 293 days of gestation to 142 days old, of both sexes and different breeds, divided into three groups, designated the naïve group up to and including the day of birth, the adapting group from 2 days up to and including 14 days old, and the loaded group from 15 days and older. The distal tibia was sawn into parasagittal slabs and the cranial half of the central slab from the intermediate ridge was examined by light microscopy and immunohistochemical staining for collagen type I. Presence, completeness and location of the collagen ring was compared, as was the quantity of perivascular mesenchymal cells. An eosinophilic ring present on HE-stained sections was seen in every single fetus and foal examined, which corresponded to collagen type I in immunostained sections. A higher proportion of cartilage canals were surrounded by an eosinophilic ring in the naïve and adapting groups at 73 and 76%, respectively, compared with the loaded group at 51%. When considering only patent canals, the proportion of canals with an eosinophilic ring was higher in the adapting and loaded than the naïve group of foals. The ring was present around 90 and 81% of patent canals in the deep and middle layers, respectively, compared with 58% in the superficial layer, and the ring was more often complete around deep compared with superficial canals. The ring was absent or partial around chondrifying canals. When an eosinophilic ring was present around patent canals, it was more common for the canal to contain one or more layers of perivascular mesenchymal cells rather than few to no layers. It was also more common for the collagen ring to be more complete around canals that contained many as opposed to few mesenchymal cells. In conclusion, the proportion of cartilage canals that had an eosinophilic ring was similar in all three groups of fetuses and foals, indicating that the presence of the collagen ring was mostly programmed, although some adaptation was evident. The ring was more often present around deep, compared with superficial canals, indicating a role in preparation for ossification. The collagen ring appeared to be produced by perivascular mesenchymal cells.

Lesions found at routine meat inspection on finishing pigs are associated with production system

Pigs raised under free-range conditions are expected to experience a higher level of animal welfare than conventionally raised pigs. However, free-range conditions may challenge prevention and treatment of diseases. In order to identify disease problems associated with raising conditions, this study compared slaughter lesions in pigs from conventional indoor, conventional free-range and organic free-range production systems. The study used data from 1,096,756 pigs slaughtered at one Danish abattoir from 1 January 2013 to 31 December 2015. Associations between production system and lesions at slaughter were tested in statistical models taking year, season and herd of origin into account. Both conventional free-range and organic free-range production systems were associated with increased population averaged odd ratios (OR_PA) for several lesions compared with conventional indoor systems. Pigs raised in conventional free-range and organic free-range production systems had higher odds for white liver-spots (OR_PA, 5-7), tail lesions (OR_PA, 3-4), arthritis (OR_PA, 3), skin lesions (OR_PA, 3), bone fractures (OR_PA, 2), septicaemia (OR_PA, 1.1-1.5) and abscesses (OR_PA, 1.1-1.3) at slaughter. Pairwise comparisons of the two free-range production systems did not reveal statistically significant differences (P>0.05). In all three production systems, airway infection was the most prevalent disease complex. In contrast to previous studies, this study did not find any association between airway infection and type of production (P>0.05). Three lesions (leg swellings (OR_PA, 0.4-0.5), hernia (OR_PA, 0.7-0.8) and hoof abscess (OR_PA, 0.7-0.9)) had lower ORs in conventional free-range and organic free-range production compared with conventional indoor production. There was a marked herd effect (intraclass correlation coefficients 21-35%) on the occurrence of white liver-spots, tail lesions, skin lesions and airway infections. These results suggest possibilities for herd-level management interventions of the problems studied.

EMA and EFSA Joint Scientific Opinion on measures to reduce the need to use antimicrobial agents in animal husbandry in the European Union, and the resulting impacts on food safety (RONAFA)

EFSA and EMA have jointly reviewed measures taken in the EU to reduce the need for and use of antimicrobials in food-producing animals, and the resultant impacts on antimicrobial resistance (AMR). Reduction strategies have been implemented successfully in some Member States. Such strategies include national reduction targets, benchmarking of antimicrobial use, controls on prescribing and restrictions on use of specific critically important antimicrobials, together with improvements to animal husbandry and disease prevention and control measures. Due to the multiplicity of factors contributing to AMR, the impact of any single measure is difficult to quantify, although there is evidence of an association between reduction in antimicrobial use and reduced AMR. To minimise antimicrobial use, a multifaceted integrated approach should be implemented, adapted to local circumstances. Recommended options (non-prioritised) include: development of national strategies; harmonised systems for monitoring antimicrobial use and AMR development; establishing national targets for antimicrobial use reduction; use of on-farm health plans; increasing the responsibility of veterinarians for antimicrobial prescribing; training, education and raising public awareness; increasing the availability of rapid and reliable diagnostics; improving husbandry and management procedures for disease prevention and control; rethinking livestock production systems to reduce inherent disease risk. A limited number of studies provide robust evidence of alternatives to antimicrobials that positively influence health parameters. Possible alternatives include probiotics and prebiotics, competitive exclusion, bacteriophages, immunomodulators, organic acids and teat sealants. Development of a legislative framework that permits the use of specific products as alternatives should be considered. Further research to evaluate the potential of alternative farming systems on reducing AMR is also recommended. Animals suffering from bacterial infections should only be treated with antimicrobials based on veterinary diagnosis and prescription. Options should be reviewed to phase out most preventive use of antimicrobials and to reduce and refine metaphylaxis by applying recognised alternative measures.

The benefits and limitations of animal models for translational research in cartilage repair

Much research is currently ongoing into new therapies for cartilage defect repair with new biomaterials frequently appearing which purport to have significant regenerative capacity. These biomaterials may be classified as medical devices, and as such must undergo rigorous testing before they are implanted in humans. A large part of this testing involves in vitro trials and biomechanical testing. However, in order to bridge the gap between the lab and the clinic, in vivo preclinical trials are required, and usually demanded by regulatory approval bodies. This review examines the in vivo models in current use for cartilage defect repair testing and the relevance of each in the context of generated results and applicability to bringing the device to clinical practice. Some of the preclinical models currently used include murine, leporine, ovine, caprine, porcine, canine, and equine models. Each of these has advantages and disadvantages in terms of animal husbandry, cartilage thickness, joint biomechanics and ethical and licencing issues. This review will examine the strengths and weaknesses of the various animal models currently in use in preclinical studies of cartilage repair.

Osteochondrosis, but not lameness, is more frequent among free-range pigs than confined herd-mates

BACKGROUND

Organic pig production is expanding and amongst the objectives of organic farming are enhancing animal health and welfare. However, some studies have reported a higher prevalence of lameness and joint condemnation at slaughter in free-range/organic pigs than in conventionally raised pigs. Organic slaughter pigs have free-range housing in which indoor and outdoor access is compulsory, while in conventional farming the pigs are commonly confined to indoor pens. The present study evaluated the effects of free-range and confined housing on lameness prevalence in a herd of 106 finisher pigs, and whether osteochondrosis and Erysipelothrix rhusiopathiae associated arthritis influences these effects. We also evaluated the association between clinical lameness during the rearing period and joint condemnations at slaughter.

RESULTS

Seventy free-range and 36 confined housed fattener pigs were scored for their gait twice during the rearing period and 848 joints were evaluated post mortem. Osteochondrosis was more frequent among free-range than confined pigs (P < 0.05), and when present it was also more severe (P < 0.001). Pigs with more numerous and more severe osteochondral lesions had their gait affected more than did pigs with fewer such lesions (P < 0.05). Hence it was a paradox that we did not detect more lameness among the free-range pigs than the confined pigs. E. rhusiopathiae associated arthritis was not diagnosed. The association between gait remarks/clinical lameness and joint condemnations at slaughter was not significant.

CONCLUSIONS

The results indicate that free-range housing may have both positive and negative effects on locomotory traits. Free-range pigs may be less clinically affected by osteochondrosis than are confined pigs. One explanation for this effect may be strengthening of joint supportive tissue and pain relief promoted by exercise. Visual gait scoring missed serious joint lesions that probably were harmful to the pigs, and should therefore not be used as a sole indicator of joint/leg health in welfare inspection of pigs. The association between gait scores and joint condemnation appeared to be poor. This study was limited to one herd, and so more and larger studies on the effects of free-range housing on lameness severity and osteochondrosis development in pigs are recommended.

An Update on the Pathogenesis of Osteochondrosis

Osteochondrosis is defined as a focal disturbance in endochondral ossification. The cartilage superficial to an osteochondrosis lesion can fracture, giving rise to fragments in joints known as osteochondrosis dissecans (OCD). In pigs and horses, it has been confirmed that the disturbance in ossification is the result of failure of the blood supply to epiphyseal growth cartilage and associated ischemic chondronecrosis. The earliest lesion following vascular failure is an area of ischemic chondronecrosis at an intermediate depth of the growth cartilage (osteochondrosis latens) that is detectable ex vivo, indirectly using contrast-enhanced micro- and conventional computed tomography (CT) or directly using adiabatic T1ρ magnetic resonance imaging. More chronic lesions of ischemic chondronecrosis within the ossification front (osteochondrosis manifesta) are detectable by the same techniques and have also been followed longitudinally in pigs using plain CT. The results confirm that lesions sometimes undergo spontaneous resolution, and in combination, CT and histology observations indicate that this occurs by filling of radiolucent defects with bone from separate centers of endochondral ossification that form superficial to lesions and by phagocytosis and intramembranous ossification of granulation tissue that forms deep to lesions. Research is currently aimed at discovering the cause of the vascular failure in osteochondrosis, and studies of spontaneous lesions suggest that failure is associated with the process of incorporating blood vessels into the advancing ossification front during growth. Experimental studies also show that bacteremia can lead to vascular occlusion. Future challenges are to differentiate between causes of vascular failure and to discover the nature of the heritable predisposition for osteochondrosis.