Principles of Animal Nutrition: Lipids, Proteins, Energy Metabolism, and Macro-Minerals

Comprehensive vocabulary flashcards covering macro-minerals, bioenergetics, protein digestion and metabolism, and lipid structure, digestion, and absorption from the ANSI 3543 Animal Nutrition course.

Simple Lipids

Esters of fatty acids with glycerol (such as oils) or alcohols (such as waxes).

Complex Lipids

Esters of fatty acids with an alcohol containing additional non-lipid groups, including glycolipids and phospholipids.

Glycolipids

Complex lipids composed of glycerol, two fatty acids, and a carbohydrate/sugar moiety, accounting for greater than $60\%$ of lipids in forage plants.

Derived Lipids

Substances obtained from the hydrolysis of simple or complex lipids, such as fatty acids, glycerol, and other alcohols.

Saturated Fatty Acids

Fatty acids in which every carbon atom along the hydrocarbon chain (excluding the carboxyl carbon) is bonded to two hydrogen atoms, containing no double bonds.

Unsaturated Fatty Acids

Fatty acids containing one or more pairs of carbon atoms joined by double bonds where hydrogen atoms have been removed, occurring as cis or trans isomers.

Branched-Chain Fatty Acids

Fatty acids containing methyl branching points and often odd numbers of carbons, synthesized by microorganisms and present in the tissues of ruminants.

Triglycerides

Esters of glycerol and three fatty acids that serve as the primary storage form of lipid in animal body tissues.

Phospholipids

Amphipathic lipids composed of glycerol, fatty acids, a phosphoric acid group, and a nitrogenous base or alcohol, serving as major structural components of biological membranes.

Sterols

Complex polycyclic lipids characterized by a four-ring steroid nucleus, of which cholesterol is the most abundant in animal tissues.

Essential Fatty Acids (EFA)

Dietary required polyunsaturated fatty acids that animals cannot synthesize in sufficient quantities, including linoleic acid ($C18:2$) and linolenic acid ($C18:3$).

Mixed Micelles

Polymolecular aggregates composed of monoglycerides, free fatty acids, bile salts, and cholesterol that facilitate passive diffusion of lipids across the unstirred water layer into enterocytes.

Chylomicrons

Large lipoprotein particles synthesized inside mucosal cells composed of approximately $80\%$ triglycerides, $11\%$ cholesterol, $7\%$ phospholipids, and a $2\%$ protein coat, which enter the lacteals via reverse pinocytosis.

Lipemia

A marked increase in the concentration of lipids circulating in the blood following the digestion and absorption of a dietary fat load.

Lipoproteins

Macromolecular complexes synthesized in the liver and small intestine that transport hydrophobic lipids through blood plasma, increasing in density as protein proportion increases.

Lipoprotein Lipase (LPL)

An endothelial enzyme activated by insulin that hydrolyzes circulating triglycerides in lipoproteins into free fatty acids for cellular uptake by adipocytes and muscle tissue.

Collagen

A water-insoluble fibrous structural protein high in proline and hydroxyproline that exhibits shrinkage upon heating and increases in tissue concentration as animals age.

Elastin

A rubberlike, water-insoluble structural protein found in combination with collagen in ligaments and artery walls that stretches readily but breaks more easily than collagen at its elastic limit.

Contractile Proteins

Muscle proteins comprising actin, tropomyosin B, and myosin; myosin constitutes the primary component of thick filaments and functions as an ATPase.

Keratins

Indigestible fibrous proteins found in wool, hair, feathers, hooves, horns, claws, and beaks that are resistant to acid, alkali, heat, and digestive enzymes.

Prions

Proteinaceous infectious particles lacking nucleic acids that are composed of an abnormal isoform of the normal cellular prion protein ($PrP$), responsible for diseases like scrapie and chronic wasting disease.

Zymogens

Inactive enzyme precursors, such as pepsinogen and trypsinogen, secreted by gastric or pancreatic cells that require selective proteolytic cleavage to become active digestive proteases.

Deamination

The enzymatic removal of the amino group ($-\text{NH}_2$) from the carbon skeleton of an amino acid, releasing free ammonia ($\text{NH}_3$).

Transamination

The transfer of an amino group from an amino acid to the carbon skeleton of a keto acid, enabling the synthesis of nonessential amino acids.

Urea Cycle

A metabolic pathway occurring predominantly in the liver and enterocytes that converts toxic ammonia and carbon dioxide into urea for urinary excretion in mammals.

Gross Energy (GE)

The total heat produced from the complete oxidation of a feedstuff or nutrient, measured using an oxygen bomb calorimeter.

Digestible Energy (DE)

The proportion of gross intake energy retained after accounting for fecal energy losses, calculated as $\text{Intake Energy (IE)} - \text{Fecal Energy (FE)}$.

Metabolizable Energy (ME)

Energy calculated by subtracting fecal energy (FE), urinary energy (UE), and combustible gas/methane energy from gross intake energy.

Net Energy (NE)

The portion of feed energy fully available to an animal for maintenance and productive functions, calculated as $\text{ME} - \text{Heat Increment (HI)} - \text{Heat of Fermentation (HF)}$.

Basal Metabolism

The minimum energy expenditure required to sustain vital bodily functions, measured in an animal in a postabsorptive state, in complete muscular repose, and within a thermoneutral environment.

Metabolic Weight

Body weight scaled to the exponent $BW^{0.75}$, used to estimate basal heat production and compare metabolic energy expenditure across animals of varying body sizes.

Maintenance Energy

The energy requirement at which neither gain nor loss in body energy reserves occurs, comprising basal metabolic rate (BMR), the thermic effect of food (TEF), and physical activity.

Macro-Minerals

Inorganic elements required in relatively large amounts in the animal diet: calcium (Ca), phosphorus (P), sodium (Na), chlorine (Cl), potassium (K), magnesium (Mg), and sulfur (S).

Parathyroid Hormone (PTH)

A peptide hormone secreted in response to decreased plasma calcium concentrations that elevates blood calcium by stimulating bone resorption, renal reabsorption, and active vitamin D synthesis.

Calcitonin

A hormone secreted by the thyroid gland in response to elevated plasma calcium levels that suppresses bone resorption to lower circulating blood calcium.

Rickets

A skeletal disorder of young, growing animals caused by calcium, phosphorus, or vitamin D deficiency, resulting in soft, deformed, and poorly calcified bones.

Osteomalacia

A metabolic bone disease occurring in adult animals characterized by excessive demineralization and softening of mature skeletal structures due to calcium or phosphorus depletion.

Nutritional Secondary Hyperparathyroidism

A pathology caused by low calcium intake or an excessive dietary phosphorus-to-calcium ratio that drives chronic parathyroid stimulation and bone resorption, manifesting as big head disease in horses.

Milk Fever

A severe acute hypocalcemic state in periparturient dairy cows characterized by tetany, loss of muscle control, recumbency, and convulsions caused by sudden calcium demand for colostrum and milk production.

Pica

An abnormal depraved appetite characterized by the craving and chewing of non-food objects like wood, soil, or bones, frequently caused by chronic phosphorus deficiency.

Lipoproteins

Macromolecular complexes synthesized in the liver and small intestine that transport hydrophobic lipids through blood plasma.

Lipoprotein Density Determinant

The biochemical relationship whereby circulating lipid-protein complexes increase in density as the relative proportion of protein increases and lipid content decreases.

Chylomicrons

Large lipid transport particles synthesized inside intestinal enterocytes consisting of approximately $80\%$ triglycerides, $11\%$ cholesterol, $7\%$ phospholipids, and a $2\%$ protein coat.

Very Low-Density Lipoproteins (VLDL)

Circulating complexes synthesized primarily in the liver to transport endogenous triglycerides to extrahepatic tissues.

Intermediate-Density Lipoproteins (IDL)

Transient vascular particles formed during the conversion of VLDL to LDL as core triglycerides are progressively hydrolyzed.

Low-Density Lipoproteins (LDL)

Cholesterol-rich vascular particles derived from the catabolism of VLDL and IDL that transport cholesterol to peripheral body tissues.

High-Density Lipoproteins (HDL)

Circulating complexes containing the highest proportion of protein and lowest proportion of lipid that mediate reverse cholesterol transport back to the liver.

Apoproteins

Surface protein components (including classes A, B, and E) embedded on lipid transport particles that maintain structural stability and mediate receptor binding.

Lipoprotein Lipase (LPL)

A capillary endothelial enzyme activated by insulin that hydrolyzes circulating triglycerides within lipoproteins into free fatty acids for cellular uptake.

Pancreatic Lipase

A digestive enzyme secreted into the duodenum that hydrolyzes emulsified dietary triglycerides into free fatty acids and monoglycerides.

Zymogens

Inactive enzyme precursors secreted by gastric or pancreatic cells that require selective proteolytic cleavage to become active digestive proteases.

Pepsinogen

The inactive proenzyme secreted by gastric chief cells that undergoes cleavage in the presence of hydrochloric acid ($\text{HCl}$).

Pepsin

The primary active gastric endopeptidase that initiates protein digestion by cleaving intact dietary proteins into smaller polypeptides in an acidic environment.

Enterokinase

A brush border enzyme of the duodenal mucosa that initiates the pancreatic protease cascade by cleaving trypsinogen into its active form.

Trypsinogen

The inactive pancreatic precursor that is cleaved by mucosal enterokinase in the duodenum.

Trypsin

An active pancreatic endopeptidase that cleaves internal peptide bonds and autocatalytically activates chymotrypsinogen and procarboxypeptidase.

Chymotrypsinogen

An inactive pancreatic precursor that undergoes proteolytic activation by trypsin in the small intestine.

Chymotrypsin

An active pancreatic endopeptidase activated by trypsin that hydrolyzes internal peptide bonds of dietary proteins in the duodenum.

Procarboxypeptidase

The inactive pancreatic precursor that is converted into an active exopeptidase via proteolytic cleavage by trypsin.

Carboxypeptidase

A pancreatic exopeptidase that hydrolyzes terminal peptide bonds sequentially from the carboxyl end of polypeptide chains.

Brush Border Peptidases

Microvillar digestive enzymes of the small intestine, including aminopeptidases and di/tripeptidases, that cleave small peptides into absorbable free amino acids.