Non-purulent arthritis in Danish slaughter pigs. I. A study of field cases

Programmed cell death-1-modified pig developed using electroporation-mediated gene editing for in vitro fertilized zygotes

Programmed cell death-1 (PD-1) is an immunoinhibitory receptor required to suppress inappropriate immune responses such as autoimmunity. Immune checkpoint antibodies that augment the PD-1 pathway lead to immune-related adverse events (irAEs), organ non-specific side effects due to autoimmune activation in humans. In this study, we generated a PD-1 mutant pig using electroporation-mediated introduction of the CRISPR/Cas9 system into porcine zygotes to evaluate the PD-1 gene deficiency phenotype. We optimized the efficient guide RNAs (gRNAs) targeting PD-1 in zygotes and transferred electroporated embryos with the optimized gRNAs and Cas9 into recipient gilts. One recipient gilt became pregnant and gave birth to two piglets. Sequencing analysis revealed that both piglets were biallelic mutants. At 18 mo of age, one pig showed non-purulent arthritis of the left elbow/knee joint and oligozoospermia, presumably related to PD-1 modification. Although this study has a limitation because of the small number of cases, our phenotypic analysis of PD-1 modification in pigs will provide significant insight into human medicine and PD-1-deficient pigs can be beneficial models for studying human irAEs.

An object-oriented Bayesian network modeling the causes of leg disorders in finisher herds

The implementation of an effective control strategy against disease in a finisher herd requires knowledge regarding the disease level in the herd. A Bayesian network was constructed that can estimate risk indexes for three cause-categories of leg disorders in a finisher herd. The cause-categories of leg disorders were divided into infectious causes (arthritis caused by infectious pathogens), physical causes (e.g. fracture and claw lesions), and inherited causes (osteochondrosis). Information about the herd (e.g. the herd size, floor type and number of suppliers) and information about individual pigs (e.g. results from diagnostic tests) were used to estimate the most likely cause of leg disorders at herd level. As information to the model originated from two different levels, we used an object-oriented structure in order to ease the specification of the Bayesian network. Hence, a Herd class and a Pig class comprised the basic components of the object-oriented structure. The causal structure of the model was based on evidence from published literature. The conditional probabilities used in the model were elicited from experts within the field and from the published literature. To illustrate the behaviour of the model, we investigated the value of different levels of evidence in two fictitious herds with different herd characteristics related to the risk of leg disorders (e.g. purchase policy, production type and the stocking density in pens). The model enabled us to demonstrate the value of performing systematic collection of additional information (i.e. clinical, pathological and bacteriological examination) when identifying causes of leg disorders at herd level.

Mycoplasma hyosynoviae arthritis in grower-finisher pigs

The aetiology of acute lameness in pigs 3-5 months of age in nine Danish herds with high incidences of lameness was investigated. Eighty-seven acutely lame pigs, that exhibited lameness of varying degree in the hind legs, were selected. Non-lame pigs were matched on pen, sex and weight. The lame pigs had soft fluctuating joint swellings (odds ratio (OR), 7.21; 95% confidence interval (CI), 3.41-15.47). No indication of suppurative arthritis was observed. Joint infection with Mycoplasma hyosynoviae was found by culture in 20% (17 of 86) of the lame pigs and in 8% (seven of 83) of the non-lame pigs. Lameness and joint infection with M. hyosynoviae were significantly associated. Other ordinary bacteria were not found in any case. Macroscopic osteochondrotic lesions were observed at slaughter in 47% (37 of 78) of the previously lame pigs and in 35% (55 of 158) of an enlarged group without history of lameness. The cubital joints were most frequently affected and a history of hind leg lameness was not statistically associated with osteochondrotic lesions at slaughter (OR, 1.69; 95% CI, (1.94-3.05), or joint infection with M. hyosynoviae at slaughter (OR, 0.88; 95% CI, 0.31-2.40). Arthritis due to M. hyosynoviae infection was the primary cause of acute and severe lameness in grower-finisher pigs. Moreover, M. byosynoviae was isolated from joints of several pigs without signs of lameness. This suggests that M. hyosynoriae may be present in joints without provoking clinical illness. The mean daily incidence of treatments due to lameness in the herds was 5.4 per 1,000 pigs. Joint disease implied 30-90 min extra labour for surveillance and treatment every day per 1,000 pigs, and 5% of the affected individuals were euthanized due to lameness. The average daily weight gains in the selected pigs until slaughter seemed unaffected by the lameness.

The effects of health classification and housing and management of feeder pigs on performance and meat inspection findings of all-in-all-out swine-finishing herds

The effects of health classification and of housing and management on performance and meat inspection findings were studied in 166 all-in-all-out finishing herds in Finland in 1995 and 1998. Producers could buy either health-classified (certified free of certain diseases) or standard-class pigs for their farms. Herds that had attained a certain level of housing and management were eligible to join the LSO 2000 management system for finishing herds. In 1995, none of the study herds were LSO 2000 units. In 1998, 76 of them had become LSO 2000 units, while 90 had remained as non-LSO 2000 units. Continuous outcome variables (daily gain and time in the finishing unit) were analysed with a mixed-model procedure with repeated measurements from the same farms. Discrete variables were analysed either with Poisson regression (mortality, whole- and partial-carcass condemnations, organ condemnations, arthritis, abscesses) or logistic regression (liver condemnations, pneumonia, pleuritis). The models were adjusted for the year, size of the herd and the average slaughter weight of the batch. The benefits obtained by the health classification of the feeder pigs included a substantial increase in daily gain (37g, about 5%) and decrease in time in the finishing unit (4 days, about 4%), decrease in mortality (odds ratio, OR 0.68), a substantial decrease in pneumonia (OR 0.37) and pleuritis (OR 0.60), and a substantial decrease in liver (OR 0.45) and organ (OR 0.72) condemnations. Classification of the pigs did not have an effect on the prevalence of whole-carcass condemnations, arthritis or abscesses. The health-classified pigs had, unexpectedly, more partial-carcass condemnations (OR 1.15) than the standard-class pigs. The obtained benefits of the LSO 2000 units were an increase in daily gain (14g, about 2%), decrease in time in the finishing unit (2 days, about 2%), a decrease in mortality (OR 0.69) and a decrease in whole-carcass (OR 0.69) and partial-carcass (OR 0.81) condemnations. The LSO 2000 units did not have any advantage over the non-LSO 2000 units in their prevalence of liver or organ condemnations, arthritis, abscesses, pneumonia or pleuritis.

Meat safety consequences of implementing visual postmortem meat inspection procedures in Danish slaughter pigs

The consequences of a change from a traditional meat inspection procedure, including manual handling, palpation and incision, to an entirely visual postmortem meat inspection procedure in Danish slaughter pigs were assessed by a comparative study of the two methods in 183,383 slaughter pigs. Out of 58 lesion codes (selected with a prevalence > or = 5.5 x 10(-5)), 26 (45 per cent) were assessed either as merely aesthetic or as the healed stage of an earlier lesion and nine (15 per cent) as active, but local processes, occurring only in non-edible tissue. Five lesion codes (9 per cent) were assessed as active, non-abscessal processes occurring in edible tissue, caused by swine-specific pathogens and 10 (17 per cent) were abscessal or pyaemic lesions occurring in edible tissue. Seven lesion codes (12 per cent) may be associated with consumer health hazards (two frequently and five rarely), and one with occupational health hazards. It was estimated that per 1000 carcases, an additional 2.5 with abscessal or pyaemic lesions (in edible tissue) containing Staphylococcus aureus, 4 x 10(-4) containing ochratoxin, 0.2 with arthritis due to Erysipelothrix rhusiopathiae, 0.1 with caseous lymphadenitis, 0.7 faecally contaminated with Salmonella species, and 3.4 faecally contaminated with Yersinia enterocolitica would remain undetected as a result of changing from the traditional to the visual inspection procedure. Two valuable reasons for implementing a visual control system are the potential for decreased cross-contamination (no handling, cutting and incision) and reduced inspection costs. The resources released as a result may be reallocated to hygiene and surveillance programmes.