Animal Nutrition, Digestion, and Mammary Gland Physiology

A comprehensive set of vocabulary flashcards covering key terms and definitions related to animal nutrition, digestive physiology of monogastric and ruminant species, absorption and metabolism of nutrients, and mammary gland development, anatomy, and health.

Nutrition

Provision of nutrients as fuel, raw materials, and essential molecules to support life.

Fuel (Nutritional Need)

Dietary component used to generate ATP for cellular energy.

Raw Materials (Nutritional Need)

Diet‐supplied building blocks required for biosynthesis of tissues and secretions.

Essential Nutrients

Dietary molecules needed to drive or assist chemical reactions that the body cannot synthesize.

ATP (Adenosine Triphosphate)

Immediate energy currency generated by oxidation of nutrients; not a storage molecule.

Basal Metabolism

Minimum energy expenditure required to maintain vital body functions at rest.

Co-factor

Metal ion or molecule that binds enzymes and is essential for their biological activity.

Coenzyme

Organic co-factor (often vitamin derivative) assisting enzyme-catalysed reactions.

Folic Acid (Vitamin B9)

Vitamin coenzyme required for DNA base synthesis.

Cytochrome

Iron-containing protein complex involved in oxidation–reduction reactions.

Digestion

Mechanical and chemical breakdown of food into absorbable molecules.

Absorption

Movement of digested nutrients across gastrointestinal epithelium into blood or lymph.

Monogastric

Animal with a single, simple stomach that cannot digest fibre extensively.

Ruminant

Animal with a multi-compartmented foregut that ferments fibrous diets.

Pre-gastric Fermenter

Species in which microbial fermentation occurs before the true stomach (e.g., cow, sheep).

Post-gastric Fermenter

Species where fermentation occurs in caecum/large intestine (e.g., horse, pig).

Peristalsis

Wavelike muscular contractions that move food through the digestive tract.

Salivary Amylase

Enzyme in saliva that begins starch digestion in some monogastrics.

Pepsin

Active gastric protease formed from pepsinogen in acidic stomach environment.

Pancreatic Amylase

Enzyme that hydrolyses non-fibre polysaccharides in the small intestine.

Disaccharidase

Brush-border enzyme that splits disaccharides into monosaccharides.

Volatile Fatty Acids (VFA)

Acetate, propionate, butyrate produced by microbial fermentation of carbohydrates.

Cholecystokinin (CCK)

Duodenal hormone that stimulates pancreatic enzyme release and gallbladder contraction.

Secretin

Hormone triggering pancreatic bicarbonate secretion to neutralise acid chyme.

Enterogastrone

Duodenal hormone that inhibits stomach motility and acid secretion when fat enters.

Trypsin

Pancreatic protease activated in small intestine; cleaves peptide bonds.

Lipase

Pancreatic enzyme that hydrolyses triglycerides into fatty acids and monoglycerides.

Bile Salts

Detergent molecules from liver/gallbladder that emulsify fats for digestion.

Micelle

Aggregate of bile salts with fatty acids/monoglycerides facilitating fat absorption.

Chylomicron

Lipoprotein particle transporting re-esterified triglycerides via lymph from intestine.

Simple Diffusion

Passive movement of molecules from high to low concentration without carrier.

Facilitated Diffusion

Passive transport via specific membrane proteins down concentration gradient.

Active Transport

Energy-requiring movement of substances against concentration gradient via carriers.

Critical Particle Size

Maximum feed particle dimension (<1–2 mm) allowed to pass from rumen to omasum.

Rumination

Process of regurgitating, rechewing, and reswallowing cud to reduce feed particle size.

Rumen

First and largest ruminant stomach compartment; major site of fermentation.

Reticulum

Honeycomb-lined foregut chamber that forms food bolus and initiates regurgitation.

Omasum

Folded foregut compartment absorbing water and VFAs; filters small particles.

Abomasum

True gastric stomach of ruminants secreting HCl and proteolytic enzymes.

Reticular Groove

Milk bypass channel in suckling ruminants directing milk to abomasum.

Neutral Detergent Fibre (NDF)

Forage fraction containing hemicellulose, cellulose, lignin after neutral detergent treatment.

Acid Detergent Fibre (ADF)

Fraction containing cellulose and lignin remaining after acid detergent extraction.

Kjeldahl Method

Chemical analysis estimating crude protein via total nitrogen × 6.25.

Dumas Method

Combustion technique to measure nitrogen content for protein estimation.

Ether Extract

Proximate analysis fraction representing crude fat.

Crude Fibre

Residue of feed after acid–alkali digestion; estimates indigestible fibre.

Nitrogen-Free Extract (NFE)

Calculated carbohydrate fraction: 1000 − (ash + crude protein + fat + crude fibre).

Pentose Phosphate Pathway

Metabolic route that generates NADPH and ribose sugars from glucose.

Gluconeogenesis

Synthesis of glucose from non-carbohydrate precursors (e.g., propionate in ruminants).

Ketone Body

Water-soluble molecule (e.g., β-hydroxybutyrate) produced from fatty acid metabolism.

Triglyceride

Storage lipid formed by esterification of glycerol with three fatty acids.

Cholesterol

Sterol synthesized from acetyl-CoA; precursor of bile acids and steroid hormones.

Lactation

Period of milk secretion by mammary gland following parturition.

Mammogenesis

Growth and development of mammary gland tissue through life stages.

Parenchyma (Mammary)

Secretory and ductal tissue responsible for milk synthesis and drainage.

Stroma (Mammary)

Supportive tissue of mammary gland including connective tissue, fat, vessels, nerves.

Alveolus (Mammary)

Milk-producing sac lined by epithelial cells and surrounded by myoepithelial cells.

Myoepithelial Cell

Contractile cell surrounding alveolus; squeezes milk into duct upon oxytocin stimulus.

Lobule

Cluster of alveoli drained by a common duct.

Gland Cistern

Mammary cavity receiving milk from ducts before passage to teat cistern.

Teat Cistern

Milk reservoir within teat above streak canal.

Streak Canal

Narrow canal at teat tip acting as barrier against milk leakage and pathogens.

Keratin Plug

Protective material in streak canal providing physical and antibacterial defense.

Milk Ejection Reflex

Oxytocin-mediated contraction of myoepithelial cells triggered by teat stimulation.

Involution (Mammary)

Regression of secretory tissue and cessation of milk synthesis after weaning or drying off.

Dry Period

Non-lactating interval (≈40–60 days in cows) necessary for gland rejuvenation before next lactation.

Somatic Cell Count (SCC)

Number of leukocytes and epithelial cells per mL of milk; indicator of udder health.

Mastitis

Inflammation of mammary tissue due to infection, raising SCC and reducing milk yield.

Streptococcus uberis

Environmental bacterium commonly causing mastitis in New Zealand dairy cows.

Staphylococcus aureus

Contagious mastitis pathogen transmitted cow-to-cow, often via milking equipment.

Lymph

Clear fluid transporting fats, proteins, and antigens; drains interstitial fluid to bloodstream.

Medial Suspensory Ligament

Elastic ligament supporting the udder against abdominal wall; can weaken over time.

Milk Vein (Superficial Epigastric Vein)

Prominent vein draining blood from udder; size not a reliable milking ability indicator.

Genitofemoral Nerve

Primary sensory and autonomic nerve supplying the udder.

Calving Interval

Time between successive calvings; affects mammary development and milk yield.

Allometric Growth (Mammary)

Growth rate of mammary tissue faster than overall body growth (≈4 : 1 at puberty).

Isometric Growth (Mammary)

Mammary growth proportional to body growth (1 : 1) before puberty.

Canalisation

Formation of lumens within primary and secondary sprouts during fetal mammary development.

Fat Pad (Mammary)

Adipose region housing vasculature and influencing postnatal mammary parenchymal growth.