Animal Science test 1 L2-L11

What are the six classes of nutrients?

Water, carbohydrates, protein, fat, minerals, vitamins.

What are the main types of animal feeds?

Forages (pasture, silage), concentrates (grains, meals), supplements (minerals, by-products).

How is digestibility calculated?

(Nutrient intake – faecal output) ÷ intake × 100.

What is Metabolisable Energy (ME)?

Gross Energy minus losses from faeces, urine, methane.

What factors affect feed quality?

Species, maturity, leaf:stem ratio, preservation method.

Typical ME values for pasture and grains?

Pasture ~10–12 MJ ME/kg DM; grains ~13–14 MJ ME/kg DM.

Difference between monogastrics and ruminants?

Monogastrics have one stomach and enzymatic digestion; ruminants have four compartments and rely on microbial fermentation.

Main compartments of a ruminant stomach?

Rumen, reticulum, omasum, abomasum.

Main VFAs produced in rumen and their uses?

Acetate (fat synthesis), propionate (glucose), butyrate (energy).

What is microbial protein?

Microbe-produced protein from NPN and amino acids, digested in the small intestine.

Ideal rumen pH?

6–7.

What happens if rumen pH drops too low?

Acidosis.

Main advantage of ruminant digestion?

Convert low-quality forage to energy via VFAs.

Main carbohydrate digestion difference: ruminant vs monogastric?

Ruminants ferment cellulose/hemicellulose to VFAs; monogastrics digest starch to glucose.

What happens to dietary protein in ruminants?

Degraded to peptides, amino acids, ammonia; excess ammonia → urea; bypass protein escapes rumen.

Examples of imported supplements?

Palm kernel expeller (PKE), molasses, grains.

Examples of supplements grown on farm?

Fodder beet, maize silage, forage crops.

How is stocking rate calculated?

Number of cows ÷ effective hectares.

How are cow feed requirements expressed?

MJ ME/day.

Why were ruminants domesticated?

Ability to turn forage into milk/meat efficiently.

Key domestication traits?

Docility, rapid growth, captive reproduction, flexible diet.

Stages of mammary gland development?

Prenatal, puberty, pregnancy, lactation, involution.

Key hormones for mammary development?

Oestrogen, progesterone, prolactin, growth hormone, IGF-1.

Mammary gland quarters and structure?

4 quarters, each with teat cistern, gland cistern, ducts, alveoli.

Function of alveoli in mammary gland?

Secretory units that produce milk.

What stimulates myoepithelial cells for milk let-down?

Oxytocin.

Main blood vessels to mammary gland?

External pudic arteries/veins, subcutaneous abdominal vein.

What supports udder weight?

Median and lateral suspensory ligaments.

Defences of teat canal?

Keratin plug, sphincter muscle.

Main milk components and sources?

Lactose (from glucose), protein (casein & whey), fat (TAGs from acetate & NEFA).

Where is lactose synthesised?

Golgi apparatus.

Where is milk protein synthesised?

Rough ER → Golgi.

Where is milk fat synthesised?

Endoplasmic reticulum (bypasses Golgi).

Which milk component is most influenced by diet?

Fat.

Why does increasing one milk component reduce another?

Competition for glucose.

Energy uses at cellular level in lactation?

Protein turnover, fat/lactose synthesis, ion pumping.

Animal-level energy needs in lactation?

Maintenance, milk production, pregnancy, body reserves.

What is negative energy balance?

Energy output exceeds intake, common in early lactation.

What is ketosis?

Excess ketone bodies from fat breakdown + low glucose.

Prevention of ketosis?

High-energy feed early lactation, glucose supplements, good body condition pre-calving.

What is milk fever?

Low blood calcium after calving.

Prevention of milk fever?

Magnesium supplement before calving, avoid over-fat cows.

Pasture grown vs eaten for utilisation example?

Utilisation = eaten ÷ grown × 100%.

Main products from sheep industry?

Meat, wool.

Wool quality factors?

Fibre diameter, length, strength, crimp, colour.

Types of wool?

Fine (Merino), medium, strong (crossbred).

NZ sheep farming systems?

Hill country breeding + finishing, intensive finishing.

Ruminant vs monogastric energy source?

Ruminants: VFAs; Monogastrics: glucose.

Energy partitioning order?

Gross Energy → Digestible Energy → Metabolisable Energy → Net Energy.

Function of monogastric stomach?

Mechanical mixing and enzymatic digestion of food with gastric juices.

Where does most digestion occur in monogastrics?

Small intestine (enzymatic digestion and absorption).

Where does microbial fermentation occur in monogastrics?

Caecum and colon (hindgut fermenters).

Examples of hindgut fermenters?

Horses, rabbits.

Why do hindgut fermenters eat faeces?

Recover microbial protein/vitamins via coprophagy.

Difference in foregut (ruminant) anatomy?

Microbial fermentation before small intestine; multi-chambered stomach.

Functions of rumen compartments?

Rumen (fermentation), Reticulum (sorting), Omasum (absorption), Abomasum (acid digestion).

Why do ruminants chew cud?

Reduce particle size, improve microbial breakdown efficiency.

Adaptation of hindgut fermenter GI tract?

Large caecum/colon for fibre fermentation.

Adaptation of high-starch diet GI tract?

Larger small intestine for enzymatic digestion.

Number of mammary gland quarters in cows?

4.

Main suspensory ligaments of udder?

Median and lateral suspensory ligaments.

Function of median suspensory ligament?

Supports udder vector, elastic.

Main blood supply to udder?

External pudic arteries and subcutaneous abdominal vein.

Lymph drainage from udder?

Supermammary lymph nodes.

Function of alveoli in udder?

Produce milk via secretory epithelial cells.

Milk flow path?

Alveoli → ducts → gland cistern → teat cistern → teat canal.

Teat canal defences?

Keratin plug, sphincter muscle.

Hormone triggering milk let-down?

Oxytocin.

Where is oxytocin released from?

Posterior pituitary.

Importance of teat sphincter closure?

Prevents microbial infection by sealing udder post-milking.