Animal and Plant Health and Welfare
Health is a system state
Define health as more than absence of disease: it includes physical, behavioural and production dimensions. Understand the disease triangle (host, pathogen, environment) and the epidemiological triad applied to herds and crops: susceptible population, virulent agent, conducive conditions. Distinguish infectious from non-infectious disorders (nutritional, metabolic, genetic, environmental, toxic). Know endemic versus exotic disease and the role of biosecurity, quarantine, isolation, sanitation and movement controls.
Animal welfare
Candidates must know the five freedoms (from hunger and thirst; from discomfort; from pain, injury and disease; to express normal behaviour; from fear and distress) and the five domains model, which adds mental state. Understand stockmanship, low-stress handling, pain relief, and welfare assessment using animal-based measures (lameness scores, body condition, hygiene, behaviour). Link welfare to productivity and to market access through quality assurance programs.
Plant health
Know integrated pest management (IPM): monitoring, thresholds, biological control, cultural control, resistant varieties, and chemical control as a last resort. Understand integrated disease management, the role of resistance and fungicide resistance, and the principles of quarantine for plant pests. Recognise abiotic symptoms (nutrient deficiency, frost, herbicide damage) that mimic disease.
Traps in questions
- Assuming any pest presence requires spraying; IPM uses economic thresholds.
- Confusing signs (the pest or pathogen itself) with symptoms (plant or animal response).
- Treating welfare as only about food and shelter, omitting behaviour and mental state.
- Recommending antibiotics for viral disease, or ignoring withholding periods for residues.
- Forgetting that biosecurity is most effective at the entry point and through routine practice, not only in emergencies.
Worked example: threshold rule
If control costs $40/ha and the crop value is $500/t with expected 15% loss without control, the loss avoided is 0.15 x yield value. For a 4 t/ha crop, loss avoided = 0.6 t x $500 = $300/ha, which exceeds $40, so control is justified. Rule of thumb: act when the value of loss avoided exceeds the cost of control, and re-monitor after treatment.