Animal Science
Domain 2: Animal Science
This domain tests anatomy and physiology, nutrition, genetics, reproduction, health, and welfare across livestock and companion species. Questions often ask you to interpret production records, select breeding stock, balance rations, or choose management practices that protect animal performance and well-being.
Core rules and concepts
- Ruminants (cattle, sheep, goats) ferment feed in the rumen; monogastrics (swine, poultry, horses) do not. Horses are hindgut fermenters, not ruminants.
- A balanced ration meets energy, protein, mineral, vitamin, and water needs for the animal's stage of production.
- Estrus is the receptive period; gestation length differs by species. Breeding soundness and proper timing affect conception rates.
- Average daily gain (ADG) = total gain ÷ days on feed. Feed conversion ratio (FCR) = feed consumed ÷ gain.
- Animal identification, biosecurity, low-stress handling, and clean water support health and welfare.
Worked example
A steer weighs 800 lb at placement and 1,200 lb after 150 days. Total gain is 400 lb, so ADG = 400 ÷ 150 = 2.67 lb/day. If the steer consumed 1,800 lb of feed during the period, FCR = 1,800 ÷ 400 = 4.5:1. A lower FCR means more efficient gain. The reasoning matters: use gain, not final weight, and keep the feed and gain periods matched.
Traps that cost marks
- Confusing ADG with final weight or with total gain.
- Using the wrong denominator in FCR, such as days instead of pounds of gain.
- Treating horses as ruminants or ignoring differences between ruminant and monogastric digestion.
- Ignoring dry-matter intake when comparing feeds with different moisture levels.