Royal College of Veterinary Surgeons Membership Exam (RCVS) Farm Animal and Production Medicine Flashcards

24 sample cards from the Farm Animal and Production Medicine deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. Define hypocalcaemia (milk fever) in the dairy cow and the typical blood calcium concentration at which clinical signs appear.

   Milk fever is periparturient hypocalcaemia from sudden lactational calcium demand. Clinical signs (recumbency, S-shaped neck, cold extremities) appear when serum calcium falls below about $1.4$ mmol/L (normal $\sim 2.1$–$2.5$ mmol/L).

2. Explain the DCAD (Dietary Cation-Anion Difference) approach to preventing milk fever and its formula.

   Feeding anionic salts in the close-up dry period induces mild metabolic acidosis, mobilising calcium. DCAD (mEq/kg DM) is approximated by: $$DCAD = (Na^{+} + K^{+}) - (Cl^{-} + S^{2-}).$$ A negative DCAD diet pre-calving reduces milk fever risk.

3. Define ketosis (acetonaemia) in dairy cows and the key ketone body measured for diagnosis.

   Ketosis is negative energy balance in early lactation causing excess ketone production. Diagnosed by blood beta-hydroxybutyrate (BHB): subclinical ketosis at BHB $\geq 1.2$ mmol/L; clinical ketosis at $\geq 3.0$ mmol/L.

4. List the main clostridial diseases prevented by multivalent ruminant clostridial vaccines.

   Blackleg (Clostridium chauvoei), black disease (C. novyi), malignant oedema (C. septicum), tetanus (C. tetani), botulism (C. botulinum), braxy (C. septicum), and pulpy kidney/enterotoxaemia (C. perfringens type D).

5. What causes pulpy kidney disease in sheep, and which animals are typically affected?

   Pulpy kidney (enterotoxaemia) is caused by Clostridium perfringens type D epsilon toxin, triggered by carbohydrate overload. It typically affects the fastest-growing, best-conditioned lambs, often causing sudden death.

6. State the UK legal minimum weaning age for piglets and a key welfare concern with early weaning.

   The EU/UK minimum weaning age is 28 days (21 days permitted only if moved to specialised, all-in/all-out, cleaned/disinfected housing). Early weaning increases post-weaning diarrhoea, stress, and tail-biting risk.

7. Name the three main agents of post-weaning enteric disease in pigs and one key control point.

   Enterotoxigenic E. coli (post-weaning diarrhoea/oedema disease), Lawsonia intracellularis (ileitis), and Brachyspira hyodysenteriae (swine dysentery). Control via gradual diet transition, hygiene, zinc/acid management, and vaccination.

8. What is the most common cause of enzootic pneumonia in pigs, and which pathogen complex does it worsen?

   Enzootic pneumonia is caused by Mycoplasma hyopneumoniae. It predisposes to the Porcine Respiratory Disease Complex (PRDC) involving PRRS virus, swine influenza, Actinobacillus pleuropneumoniae (App) and Pasteurella multocida.

9. Define the welfare and legal status of tail docking in pigs under UK law.

   Routine tail docking is prohibited; it may only be done as a last resort after other measures to reduce tail biting (enrichment, stocking density, environment) have failed and been documented. When done it must occur in the first 7 days of life.

10. Name the principal notifiable viral diseases of pigs in the UK.

    African swine fever (ASF), Classical swine fever (CSF / hog cholera), Foot-and-mouth disease, Aujeszky's disease (pseudorabies), Swine vesicular disease, and Teschen disease (porcine enterovirus encephalomyelitis).

11. Contrast African swine fever (ASF) and Classical swine fever (CSF) by causative agent.

    ASF is caused by a large DNA Asfarvirus (Asfivirus) with no widely available vaccine. CSF is caused by an RNA Pestivirus (family Flaviviridae), related to BVDV. Both cause high-mortality haemorrhagic disease and are notifiable.

12. What is the legal feeding restriction central to preventing notifiable disease introduction in pigs (the 'swill' rule)?

    It is illegal to feed catering waste, kitchen scraps, or meat/meat products to pigs (the swill feeding ban). This prevents introduction of ASF, CSF, and FMD via contaminated food of animal origin.

13. Name two major notifiable poultry diseases and their causative agents.

    Avian influenza (highly pathogenic H5/H7 influenza A viruses) and Newcastle disease (avian paramyxovirus type 1 / Avian orthoavulavirus 1). Both are notifiable to APHA.

14. Explain the difference between vertical and horizontal transmission with a poultry example of each.

    Vertical = pathogen passes from hen to progeny via the egg (e.g. Salmonella Enteritidis, Mycoplasma gallisepticum). Horizontal = spread between birds via direct contact, aerosol, faeces, or fomites (e.g. infectious bronchitis virus, avian influenza).

15. What is the purpose of an 'all-in/all-out' (AIAO) management system in intensive poultry and pig units?

    AIAO populates and depopulates a building as a single cohort, allowing complete cleaning, disinfection, and downtime between batches. This breaks pathogen cycles, prevents carry-over between age groups, and reduces antimicrobial reliance.

16. Describe biosecurity zoning using the concept of a 'line of separation' between clean and dirty areas.

    Bio-exclusion divides a unit by a line of separation: the 'dirty' (outside) area and 'clean' (inside, protected) area. People, equipment and vehicles must change/clean (boots, clothing, disinfection) when crossing, preventing pathogen entry into the protected flock/herd.

17. In population medicine, define incidence and prevalence and the relationship between them.

    Incidence = rate of NEW cases over a time period in an at-risk population. Prevalence = proportion of EXISTING cases at a point in time. At steady state: $$\text{Prevalence} \approx \text{Incidence} \times \text{Disease duration}.$$

18. Define sensitivity and specificity of a diagnostic test using their formulae.

    $$\text{Sensitivity} = \frac{TP}{TP + FN}, \qquad \text{Specificity} = \frac{TN}{TN + FP}.$$ Sensitivity is the proportion of truly diseased correctly identified; specificity is the proportion of truly healthy correctly identified.

19. Define the basic reproduction number $R_0$ and its threshold significance in epidemiology.

    $R_0$ is the average number of secondary cases produced by one infected individual in a fully susceptible population. If $R_0 > 1$ an epidemic can grow; if $R_0 < 1$ infection dies out. Control aims to reduce the effective reproduction number $R$ below 1.

20. What is the herd immunity threshold formula, and what does it represent?

    The critical proportion that must be immune to prevent spread is $$p_c = 1 - \frac{1}{R_0}.$$ Vaccinating above this fraction interrupts sustained transmission within the population.

21. State the central principle of responsible antimicrobial stewardship in farming and which classes are reserved as last resort.

    Use antimicrobials 'as little as possible, as much as necessary' — only when needed, based on diagnosis/sensitivity, avoiding routine prophylaxis. Highest Priority Critically Important Antimicrobials (HP-CIAs — fluoroquinolones, 3rd/4th-gen cephalosporins, colistin) are reserved as last resort to preserve efficacy.

22. What does 'withdrawal period' mean in food-chain safety, and why is it critical?

    The withdrawal period is the minimum time between the last administration of a veterinary medicine and slaughter (or milk/egg use) required for residues to fall below the Maximum Residue Limit (MRL). It protects consumers from harmful drug residues and is a legal requirement.

23. Describe the role of ante-mortem and post-mortem inspection in meat hygiene/food chain safety.

    Ante-mortem inspection (live, before slaughter) screens for disease, welfare and fitness for slaughter, supported by Food Chain Information (FCI). Post-mortem inspection examines carcass and offal (visual, palpation, incision) to detect disease/contamination and judge fitness for human consumption — overseen by the Official Veterinarian (OV).

24. Define stunning in the context of welfare at slaughter and give permitted methods for cattle and poultry.

    Stunning renders the animal immediately unconscious and insensible to pain before bleeding (sticking). Cattle: captive bolt (penetrative/non-penetrative) or electrical. Poultry: electrical waterbath or controlled atmosphere (gas) stunning. Insensibility must outlast the stun-to-stick interval.

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