Fundamental Nature of Lameness
Definition: An abnormal gait of musculoskeletal, neurological, or integumentary origin.
Economic & Welfare Impact: A perennial issue affecting growth rates, reproduction, and slaughter condemnations; a primary focus of animal well-being audits.
Etiological Categories: Traumatic, infectious, nutritional, or developmental/congenital.
The Diagnostic Framework (The "Four Circle" Approach)
Circle 1 (Premises): Evaluation of facility design, traffic patterns, and biosecurity.
Circle 2 (Barns): Environmental features and specific management practices.
Circle 3 (Rooms/Pens): Group health assessment, behavior, and prevalence estimates.
Circle 4 (Individual Exam): In-depth clinical examination and identifying specific causes (e.g., swollen joints).
Ancillary Tools: Restraint (snaring, sorting panels, lift chutes), sedation/anesthesia, and postmortem necropsy.
Infectious Agents (Common Bacterial Causes)
Streptococcus suis: Common primary cause of arthritis, sepsis, and meningitis; high concern due to zoonotic potential.
Glaesserella parasuis (Glässer’s Disease): Causes acute sepsis, polyserositis, and arthritis; severe in naive populations.
Mycoplasma hyosynoviae: Causes acute hind-limb lameness in pigs 10–26 weeks old; characterized by clear, yellow synovial fluid.
Mycoplasma hyorhinis: Predominant in nursery pigs (3–8 weeks); leads to polyserositis and fibrinous arthritis.
Erysipelothrix rhusiopathiae (Erysipelas): Causes acute sepsis, "diamond skin" lesions, and chronic proliferative arthritis.
Trueperella pyogenes: Ubiquitous opportunist causing abscesses and osteomyelitis.
Lameness by Production Stage
Septic Polyarthritis (Joint Ill): From bacterial entry via the umbilicus, skin abrasions, or poor hygiene during processing (tail docking, castration).
Splayleg (Spraddle Leg): Muscle immaturity at birth; treated with limb hobbling.
Congenital Tremors: Often associated with Atypical porcine pestivirus infection in naive gilts.
Locomotor dysfunction is a major contributor to nursery morbidity and mortality.
Vertebral Deformities: Kyphosis (hump back) linked to nutritional deficiencies.
Rickets: Nutritional deficiency (Vitamin D, Ca, or P) resulting in soft bones, "rachitic rosaries" on ribs, and spontaneous fractures.
Osteochondrosis: Joint lesions in rapidly growing pigs (relevant after 10 weeks of age).
Environment, Nutrition, and Management:
Flooring: Slippery floors lead to trauma; abrasive floors wear claws; gaps in slats cause digit entrapment and loss of accessory digits.
Nutritional Factors (Metabolic Bone Disease): Discrepancies in Vitamin D, Phytase, Calcium, or Phosphorus; Biotin deficiency causes weak, flaky hoof keratin.
Management Stresses: Moving/mixing pigs, overcrowding, and viral coinfections (e.g., PRRSV or Circovirus) that compromise immunity.
Therapeutic & Preventive Strategies:
Antimicrobials: Early parenteral therapy is critical for acute bacterial infections; choice based on sensitivity (e.g., penicillins, tylosin, lincomycin).
Analgesia (Supportive Care): Use of flunixin meglumine, meloxicam, or dexamethasone to relieve pain and fever.
Vaccination: Commercial vaccines (Erysipelas) or autogenous bacterins using farm-specific isolates (S. suis, G. parasuis).
Environmental Control: All-in/all-out flow, improved hygiene, and selecting appropriate flooring.