Animal and Veterinary Sciences
ASRB NET Animal and Veterinary Sciences covers animal breeding and genetics, animal nutrition, veterinary pathology and veterinary microbiology. The exam expects quantitative breeding, ration evaluation and lesion or microbe interpretation.
Core concepts
- Selection response: R = i h² σ_P = i h σ_A, where i is selection intensity, h² heritability, σ_P phenotypic standard deviation and σ_A additive genetic standard deviation.
- Annual response depends on generation interval: genetic gain per year = R divided by generation interval.
- Nutrition: a ration is balanced for energy as TDN, protein as DCP, minerals and vitamins; intake is limited by gut fill and energy density.
- Pathology: distinguish degeneration, necrosis, apoptosis and inflammation; the location and pattern of lesions narrow the diagnosis.
- Microbiology: Gram stain, colony morphology, haemolysis and biochemical tests are preliminary; confirm with serology or PCR.
Worked example
A herd has phenotypic standard deviation for yearling weight of 10 kg, h² = 0.30 and selection intensity i = 1.4. Expected response R = 1.4 × 0.30 × 10 = 4.2 kg. If the generation interval is 2 years, annual genetic gain is 4.2 divided by 2 = 2.1 kg per year. Reasoning: heritability converts phenotypic superiority into genetic superiority; intensity depends on the proportion selected.
Traps that cost marks
- Using h² as if it were the proportion of a phenotype inherited by an individual offspring.
- Adding fixed and variable costs when calculating feed cost per kg gain.
- Diagnosing bacterial disease from a Gram stain alone.
- Ignoring genotype × environment interaction when comparing breeding values.