Animal Nutrition

Nutrient classes, digestion, feed additives, lipid metabolism, mineral nutrition, vitamins, energy, nutrient calculations, and carbohydrates (ANSC 223, Lectures 1–11)

Exam 1Lectures 1–3 (top half) · Classes of Nutrients, Non-ruminant Digestion, Ruminant Animals

Classes of Nutrients

Definitions

Nutrition: series of processes by which an organism takes in and assimilates food for growth, tissue maintenance, and production (milk, eggs, wool)
Nutrient: any chemical element or compound in the diet that supports growth, reproduction, work, lactation, or maintenance of life processes
Essential nutrient: removing it from the diet causes an abnormality; adding it back eliminates the abnormality (e.g. Ca deficiency → milk fever; Ca/P/Vitamin D deficiency → rickets)
Feed = food for farm animals; Diet = mixture of feedstuffs supplying nutrients; Ration = supply of feed at a feeding or daily

Six Main Classes of Nutrients

Water

Carbohydrates

Lipids (fats)

Proteins (amino acids)

Vitamins

Minerals

Water

Animals need ~2× as much water as dry feed intake; can survive much longer without food than without water
Makes up ~60% of body; muscle tissue ~75% water, fat tissue ~15% water
Sources: drinking water, water in food, metabolic water (from C₆H₁₂O₆ → H₂O + CO₂ + ATP)
Water loss: urine (~60%), feces, skin and lungs (15–60%)
Intake increased by: lactation (dairy cow needs ~0.9 kg water per kg milk), dietary salt, heat stress

Carbohydrates

Primary source of energy; made of repeating CH₂O units; derived from plants (except lactose)
Structural carbs: cellulose, hemicellulose (high fiber, not digestible by monogastrics without hindgut fermenters or rumen)
Non-structural carbs: sugars, starch (corn = 85% carbohydrate)

Lipids

Soluble in organic solvents; provide 2.25× more energy than carbs/proteins (9.4 kcal/g vs ~4 kcal/g)
Fats: long-chain, saturated, solid at room temp (e.g. tallow)
Oils: long-chain, unsaturated, liquid at room temp (e.g. soy oil)
Functions: energy, solvent for fat-soluble vitamins (A, D, E, K), source of essential fatty acids, palatability

Protein

Most expensive nutrient added to diets. Contains C, O, H, and N (nitrogen). Source of essential amino acids. Molecular makeup involves chains of amino acids linked by peptide bonds.

Vitamins

Fat-Soluble (A, D, E, K)

Can be stored in the animal. Fortification/enrichment needed (e.g. milk fortified with Vitamin D).

Water-Soluble (8 B vitamins + Vitamin C)

Cannot be stored — must be provided daily. B vitamins synthesized by rumen microbes in ruminants.

Fortification = adding nutrients not already present. Enrichment = replenishing nutrients lost during processing.

Minerals

Macrominerals (large amounts in body)

Calcium, Sodium, Chloride, Potassium, Magnesium, Sulfur

Microminerals / Trace Minerals

Selenium, Copper, Iron, Zinc, Cobalt

Minerals must be fed in proper balance — over or underfeeding causes serious problems. Cannot be decomposed or synthesized by the body.

Forages vs Concentrates

Component	Forage (Roughage)	Concentrate (Grain)
Energy	Low	High
Protein	Low	Low–moderate
Fiber	High (stimulates rumination)	Low
Ca & K	High	Low
Fed to	Cattle, horses, sheep, exotics	Poultry, pigs, dogs, cats, fish

Feed Efficiency

Ability of an animal to convert a unit of feed into a unit of body mass. Major determinant of cost.

Animal	Gain (kg/d)	Feed (kg/d)	Feed:Gain	Gain:Feed
Chicken	0.9	1.1	1.2	0.82
Young pig	0.3	0.5	1.7	0.60
Finishing pig	1.0	2.4	2.4	0.42
Beef steer	1.6	10	6.3	0.16

Factors affecting efficiency: diet quality, age (mature animals less efficient), composition of gain (fat vs lean), endocrine status, environment, genetics.

Non-ruminant Digestion

GI Tract Types

Simple Stomach

Dogs, cats, pigs, humans. One stomach compartment.

Hindgut Fermenter

Horses, rabbits, guinea pigs, rhinoceros, elephant. Large cecum for fiber fermentation.

Avian

Chickens, turkeys. Crop → proventriculus → gizzard → short small intestine → ceca → cloaca.

Three forces acting on food in the GIT: mechanical (chewing, peristalsis), chemical (HCl, bile), enzymatic (amylase, lipase, proteases).

Stomach — Three Regions

Cardiac region: mucus secretion
Fundic region: HCl (acidifies), zymogens (pepsinogen, prorennin), mucus
Pyloric region: mucus, gastrin (hormone controlling gastric juice flow)
Zymogens are inactive enzyme precursors activated by hydrolysis (e.g. pepsinogen → pepsin)
Rennin: complex of enzymes in stomach of young pre-ruminants; curdles milk by coagulating casein into curds → retains milk longer for digestion
Lingual lipase: secreted by tongue glands; initiates fat digestion in neonates

Small Intestine

Three sections: Duodenum (digestion), Jejunum (digestion + absorption), Ileum (mostly absorption)
Villi increase surface area for absorption. Malnutrition causes villus atrophy.
Secretin (triggered by low pH) and Cholecystokinin (CCK) (triggered by lipid + peptides) secreted by duodenum

Source	Enzymes / Secretions	Substrate
Pancreas	Trypsin/Chymotrypsin/Carboxypeptidase (as zymogens), Pancreatic amylase, Pancreatic lipase + colipase	Protein, Starch, Lipid
Small intestine	Enteropeptidase (activates trypsinogen), Maltase, Sucrase, Lactase, Peptidases	Trypsinogen, Maltose, Sucrose, Lactose, Peptides
Liver/Gallbladder	Bile (bile salts)	Lipid emulsification → ↑ surface area for lipase

Absorption Mechanisms

Simple Diffusion

High → low concentration. No energy needed.

Active Transport

Against concentration gradient. Requires ATP. Important for glucose and some amino acids.

Protein-Mediated Transport

Facilitated diffusion via carrier proteins.

Hindgut Fermenters (Horses)

Large cecum (blind pouch) + large colon provide microbial fermentation of fiber
Produces short-chain VFAs (Volatile Fatty Acids), water-soluble vitamins, and protein
Only VFAs and water-soluble vitamins are absorbed from the cecum/colon
VFAs can provide over 70% of horse's energy requirement

Avian GI Tract

Crop: food storage and moistening
Proventriculus: glandular stomach (HCl + enzymes)
Gizzard: muscular stomach; mechanical breakdown using grit (sand and small stones). No sphincter separating it from duodenum.
Ceca (2): microbial fermentation, water absorption
Cloaca: common chamber for GI tract, urinary tract, and egg laying
Phytate-phosphorus (main plant P storage form) requires phytase enzyme for release

Ruminant Digestion

Exam 1 — Animals, 4-Compartment Stomach, Rumen Microbes

Ruminant Animals

True ruminants (Bovidae, Cervidae, Giraffidae): cattle, sheep, goats, bison, moose, reindeer, giraffe, wildebeest, antelope. Pseudo-ruminants (Tylopoda): camels, llamas.

Key characteristic: consume large amounts of fibrous material quickly, then rest and ruminate (chew cud). Microbial fermentation in a multi-chambered foregut makes otherwise indigestible plant cellulose available — animals cannot make cellulase, but rumen microbes can.

4-Compartment Stomach

Reticulum (Honeycomb)

Origin of contractions, rumination (regurgitation), and eructation. Traps foreign objects. No enzymes secreted.

Rumen

Large fermentation vat (~100L). Papillae for absorption. pH 6–7 maintained by saliva. Contains 500,000 billion bacteria, 50 billion protozoa. Gas produced must be released via eructation — failure causes bloat (diaphragm compression → asphyxia).

Omasum

Filters digesta flow from rumen. Laminae reduce particle size. VFAs and water absorbed. No enzymes secreted.

Abomasum (True Stomach)

Only glandular compartment. Secretes HCl, pepsin, and mucus. Lysozyme in mucus breaks down bacterial cell walls. Displaced abomasum occurs when diet is too low in forage.

Rumen Microbes & Fermentation

Strictly anaerobic environment. >60 bacterial species and 20 protozoal species are normal inhabitants.
Three niches: sugar fermenters (~3% of typical diets), fiber digesters (cellulose/hemicellulose), starch fermenters (grain diets)
Protozoa: prey on bacteria, engulf starch granules, important in N recycling
Heat of fermentation: rumen is warm; up to 10% of total energy lost as heat. Asset in cold stress, liability in heat stress.
Methane: 5–10% of ingested energy lost as CH₄. Highest with forage, lowest with grain diets. Cattle in US contribute ~20% of all atmospheric CH₄.

Exam 2Lectures 3 (bottom half)–5 · VFA Production, Feed Additives, Lipids

Ruminant Digestion (continued)

Exam 2 — VFA Production, Protein Digestion, Acidosis, Neonate Ruminants

VFA Production & Use

Fiber (forage) diet → high acetate

Acetate (C2): lipogenesis, energy. Propionate (C3): small proportion. Butyrate (C4): energy.

Starch (grain) diet → high propionate

Acetate (C2): reduced. Propionate (C3): 70–90% goes to liver → gluconeogenesis. Butyrate (C4): energy.

VFAs absorbed through rumen papillae → portal vein → liver. Propionate is primary gluconeogenic substrate in ruminants.

Protein Digestion in Rumen

Bacteria break down soluble protein to peptides and ammonia (enzymes on bacterial surface)
Bacteria synthesize microbial protein from the peptides and ammonia
Microbial protein digested in the abomasum (true stomach)
Excess ammonia → liver → urea → recycled in saliva or excreted in urine

Acidosis

Caused by: accidental grain overload, too-rapid diet change to high grain
Lactic acid accumulates (10× more acidic than VFAs) → rapid pH drop
Sub-acute ruminal acidosis (SARA): pH 5.0–5.5; Acute: pH ≤ 4.5
Below pH 6: cellulolytic and methanogenic bacteria decrease, amylolytic bacteria increase, Lactobacillus spp. increase
Prevention: ≥10% roughage in finishing rations, gradual diet transitions, buffers (NaHCO₃), ionophores

Neonate Ruminants

Born with non-functional rumen. Cleaned by mother. Rumen nearly functional at ~60 days. Suckling causes esophageal (reticular) groove to close → milk bypasses rumen directly to omasum. Diet drives rumen development: grain promotes papillae growth more than hay alone.

Feed & Food Additives

Definitions

Non-nutritive additives: any compound added to the diet for reasons other than nutrient supply
Drugs: substances intended for treatment, prevention, or diagnosis of disease — require FDA approval
GRAS (Generally Recognized As Safe): substances with published safety/utility information; efficacy must still be proven for each new product

Non-regulated Additives

Flavors / palatants

Buffers (NaHCO₃)

Organic acids (formic, propionic, citric)

Probiotics

Prebiotics

Yeast (S. cerevisiae)

Enzymes (phytase, xylanase)

Antioxidants

Regulated Additives

Antibiotics

Ionophores (ruminants)

Anthelmintics (dewormers)

Hormones

Beta-agonists (ractopamine)

Coccidiostats (poultry/cattle)

Antibiotics

Bacteriostatic (prevent growth) or bactericidal (kill bacteria)
Used as growth promotants: control sub-clinical disease, nutrient-sparing effect, metabolic effect (more ATP available)
Problem: antibiotic resistance and potential transfer to human pathogens
FDA Guidance 209/213: strict withdrawal times before market (monitored by APHIS)
Common: Oxytetracycline, Chlortetracycline, Tylosin (Tylan), Carbadox (swine)

Ionophores (Ruminants)

Allow ions to move through cell membranes of gram-positive bacteria → selectively inhibit acetate-producing and lactic acid-producing bacteria
↑ propionate, ↓ acetate in rumen → improved feed efficiency
Also reduce bloat, acidosis, coccidiosis risk, and methane production
Used in ~95% of feedlot cattle diets (fed at 10–13 g/ton)
Monensin (Rumensin): 80% market share. ↑ feed efficiency 5–10%, ↑ weight gain 2–7%
Lasalocid (Bovatec): 15% market share
Warning: Horses DO absorb ionophores — very toxic, no treatment available

Beta-Agonists (Ractopamine)

β-adrenergic agonist — shifts energy partitioning from fat to lean muscle tissue
Not an antibiotic, not a hormone. No withdrawal period.
Paylean (pigs): last 28 days before market, 4.5–9 g/ton. ↑ carcass wt 10.6 lbs, ↑ feed efficiency 7–15%, ↑ daily gains 6–20%
Optaflexx (cattle): 200–400 mg/head/day for 28–42 days. ↑ carcass wt 15–20 lbs, ↑ feed efficiency 10–15%

Buffers, Probiotics & Enzymes

Buffers: NaHCO₃ at 0.75% DM most common for dairy cattle and feedlot cattle during diet adjustment. MgO also used. Prevent rumen acidosis on high-grain diets.
Organic acids: Citric acid most common for young pigs and chicks. Lowers stomach pH → improved protein digestion, reduced pathogen incidence.
Phytase: most common added enzyme. From Aspergillus or E. coli. Releases phytate-bound phosphorus from plant feeds; ↑ P absorption 5–7%, ↓ P excretion 50–75%. Primarily for non-ruminants.
Probiotics (direct-fed microbials): live Lactobacillus, Streptococcus, Bacillus, yeast cultures. Most effective in stressed, newly weaned, or relocated animals.
Prebiotics: non-digestible ingredients (food for good bacteria); promote lactic-acid bacteria, suppress E. coli. Primarily in pet foods.
Yeast (S. cerevisiae): source of B vitamins and mannan-oligosaccharides. In dairy cattle: higher rumen pH, ↑ cellulolytic bacteria, ↑ fiber digestion, ↑ microbial protein synthesis.

Bloat

Frothy (pasture) bloat: caused by soluble proteins and saponins from legumes (clover, alfalfa) → insufficient saliva → slime production → foam traps gas. Sudden death risk. Prevention: poloxalene (Bloat Guard) = non-ionic surfactant that consolidates gas bubbles → eructation. Mineral oil also used.

Lipids

Classification of Lipids

Simple Lipids (glycerol-based)

Triacylglycerols (TAGs): 3 fatty acids ester-bonded to glycerol. >90% of dietary lipids.

Sterols: cholesterol (zoosterol), phytosterols (plants). Precursor of steroid hormones, bile acids, Vitamin D.

Compound Lipids

Phospholipids (Lecithin): major cell membrane component; amphiphilic → emulsification; body store of choline (deficiency → fatty liver).

Glycolipids: CHO + lipid; major lipids in forage leaves.

Lipoproteins: transport lipids in blood (chylomicrons, VLDL, LDL, HDL).

Non-glycerol Lipids

Waxes (surface lipids), sphingomyelins, cerebrosides, terpenes, prostaglandins.

Fatty Acids by Carbon Chain Length

Named by convention: C[length]:[double bonds], ω-[methyl-end position]. Melting point ↑ with chain length; ↓ with unsaturation (double bonds).

Formula	Name	Class	Source / Origin	Biological Role	Animal Notes
Short-Chain (C2–C6) — Volatile Fatty Acids (VFAs), water-soluble, absorbed directly into portal blood
C2:0	Acetic acid (acetate)	Sat VFA	Rumen fermentation of fiber (forage diet); vinegar	Energy (enters TCA as acetyl-CoA); substrate for lipogenesis and milk fat synthesis	60–70% of rumen VFAs on forage; ↓ on grain diets; ionophores reduce acetate production
C3:0	Propionic acid (propionate)	Sat VFA	Rumen starch fermentation (grain diet); silage	Primary gluconeogenic substrate in ruminants; enters TCA as succinyl-CoA	70–90% goes to liver on grain diet; ↑ with ionophores; critical for blood glucose maintenance in dairy cows
C4:0	Butyric acid (butyrate)	Sat VFA	Rumen fermentation; butter (3–4% of milk fat)	Energy for rumen epithelial cells and colonocytes; drives rumen papillae development	~15% of VFAs; ↑ grain diet; critical for neonatal rumen development (grain feeding initiates papillae growth)
Medium-Chain (C8–C14) — MCTs; absorbed via portal vein, bypass lymph and chylomicron packaging
C12:0	Lauric acid	Sat MCT	Coconut oil (45–55% of fat); palm kernel; some milk fat	Potent antimicrobial (gram-positive bacteria); disrupt viral lipid envelopes	Raises LDL and HDL; monolaurin antiviral; added to nursery pig diets
Long-Chain Saturated (C16–C18:0) — Solid at room temp; main storage fats in animals; absorbed via lymph as chylomicrons
C16:0	Palmitic acid	Sat	Palm oil; beef/pork tallow; de novo lipogenesis end product	Structural FA in membranes and stored fat; primary product of fatty acid synthase (FAS)	↑ LDL in excess; most abundant saturated FA in animal body
C18:0	Stearic acid	Sat	Beef tallow, cocoa butter; end product of rumen biohydrogenation	Desaturated to oleic (C18:1) by Δ9-desaturase in tissues	Uniquely does NOT raise LDL; high in ruminant fat post-biohydrogenation
Long-Chain Unsaturated (C18:1–C22:6) — Liquid at room temp; one or more double bonds
C18:1, ω-9	Oleic acid	MUFA	Olive/canola oil; lard; tallow	↓ LDL without ↓ HDL; structural membrane FA	Dominant FA in poultry and pork fat
C18:2, ω-6	Linoleic acid Essential	PUFA ω-6	Soybean, sunflower, corn oil	Skin integrity, RBC membranes, fertility; precursor to arachidonic acid (C20:4)	EFA deficiency → scaly dermatitis, poor coat; dogs/cats ≥1% DM required
C18:3, ω-3	α-Linolenic acid (ALA) Essential	PUFA ω-3	Flaxseed oil (55%), chia, green leaves	Eye and CNS structural lipid; precursor to EPA and DHA	Flaxseed feeding to hens → ω-3 enriched eggs
Very Long-Chain PUFA (C20–C22) — EFA derivatives; precursors to eicosanoids
C20:4, ω-6	Arachidonic acid (AA) Semi-essential	PUFA ω-6	Animal tissues, egg yolk	Primary eicosanoid precursor: prostaglandins, thromboxanes, leukotrienes	Cats essential: low Δ-6 desaturase → require dietary AA (≥0.02% DM)
C20:5, ω-3	EPA	PUFA ω-3	Fish oil; algae	Competes with AA for COX/LOX → less inflammatory eicosanoids; ↓ TG	Anti-inflammatory; improves fertility in mares and dairy cows
C22:6, ω-3	DHA	PUFA ω-3	Fish oil; algae; brain (40% of brain PUFA)	Neural membrane fluidity; retinal photoreceptor function; fetal brain development	Essential for neonatal brain/vision; omega-3 enriched eggs via algae meal

Eicosanoids from PUFA

From Arachidonic Acid (ω-6) — Pro-inflammatory series

PGE2, PGF2α: inflammation, fever, uterine contraction
TXA2: platelet aggregation, vasoconstriction
LTB4: neutrophil chemotaxis, bronchoconstriction

From EPA (ω-3) — Anti-inflammatory / weaker series

PGE3, PGF3α: weaker pro-inflammatory effect
TXA3: weak platelet aggregation
LTB5: weak chemotaxis

ω-3 and ω-6 compete for the same COX and LOX enzymes. Higher dietary ω-3:ω-6 ratio shifts production toward less inflammatory eicosanoids.

Lipid Digestion & Absorption

Gastric/lingual lipase begins lipid digestion in stomach (primary in neonates)
In duodenum: bile salts emulsify dietary lipids (↑ surface area)
Pancreatic lipase + colipase hydrolyze TAGs → monoacylglycerol + 2 free fatty acids
Products form micelles → absorbed across intestinal epithelium
Re-esterified into TAGs → packaged into chylomicrons → absorbed into lymph via lacteals → enter bloodstream
Lipoprotein lipase removes fatty acids from chylomicrons at capillaries → deposited in adipose or muscle

Short- and medium-chain FAs (C2–C12) bypass chylomicron packaging and are absorbed directly into the portal vein → liver.

Ruminant Lipid Considerations

Biohydrogenation: rumen microbes convert dietary unsaturated FAs → saturated FAs (adds H atoms). End product: mostly C18:0 (stearic). Produces trans FAs as intermediates.
Fatty liver disease: common in high-producing dairy cows post-partum. High free fatty acids from adipose overwhelm liver oxidation → hepatocytes fill with TAG → reduced liver function.
Ruminants have more bile acids than monogastrics, compensating for the more saturated FA profile entering the small intestine.

Exam 3Lectures 6–7 · MacroMinerals, Microminerals

MacroMinerals

Overview

7 macrominerals: Ca, P, K, Na, Cl, Mg, S — needed in large amounts (>100 mg/day), measured in % of diet
Body mineral composition: Ca = 46%, P = 29%, K/Na/S/Cl/Mg = 25% combined, trace minerals <0.3%
General functions: skeletal structure (hydroxyapatite), osmotic pressure regulation, acid-base balance, enzyme activation/cofactors
Mineral excretion routes: urine (soluble minerals), feces (insoluble/unabsorbed), milk (dairy animals), sweat

CaCalciumMost abundant mineral in body (46%)

Sources

Limestone (calcite)
Dicalcium phosphate (dical)
Fish meal, meat and bone meal
Forages (alfalfa, legumes)

Functions

99% stored in bone as hydroxyapatite [3Ca₃(PO₄)₂·Ca(OH)₂]
Blood clotting (cofactor)
Muscle contraction
Nerve impulse transmission
Regulation: calcitonin (↓ blood Ca), PTH (↑ blood Ca), Vitamin D (↑ absorption)

Deficiency

Rickets: young animals; soft, malformed bones
Osteomalacia: adults; softening of bones
Osteoporosis: reduced bone density
Milk fever (dairy cows): hypocalcemia at calving — Ca secreted in colostrum → low blood Ca → muscle paralysis, recumbency, death if untreated

PPhosphorus2nd most abundant mineral (29%)

Sources

Animal products (high bioavailability)
Dicalcium phosphate (dical)
Monocalcium phosphate (monocal)
Phytate P: main plant storage form — low bioavailability in nonruminants; phytase enzyme (Aspergillus/E. coli) cleaves it → releases P

Functions

Hydroxyapatite (bone mineralization)
Acid-base balance (HPO₄²⁻ buffer)
Phospholipids (cell membranes)
DNA, RNA, ATP energy metabolism

Deficiency / Excess

Pica (depraved appetite): chewing bones, wood, etc.
Especially a concern in tropical/subtropical soils deficient in P
Excess P: eutrophication — algae overgrowth depletes dissolved O₂ in waterways (e.g., Mississippi River drainage basin)

KPotassium3rd most abundant; 98% intracellular

Sources

Grains: 0.3–0.8%
Animal products: 0.3–2.0%
Vegetable proteins: 1.0–2.5%
Plants generally high; alfalfa >2.0%
Excess K from alfalfa can be a problem for dairy cows (worsens milk fever risk)

Functions

Na⁺/K⁺ ATPase pump (3 Na out, 2 K in per cycle)
Carbonic anhydrase (acid-base, CO₂ excretion)
Salivary amylase cofactor
Osmotic balance
Nerve impulse transmission
DCAD = ([Na⁺]+[K⁺]) − ([Cl⁻]+[S²⁻]); Na,K positive; S,Cl negative
Low DCAD pre-partum → ↓ urine pH, ↑ blood Ca, ↓ milk fever incidence

Deficiency / Excess

Deficiency: extremely rare; degeneration of vital organs, nervous disorders, diarrhea
Excess K with spring grasses: impairs Mg absorption → grass tetany (weakness, tetany)
Corn silage and cereal grains are low in K

Na / ClSodium & ChlorineTable salt (NaCl)

Sodium (Na)

Sources

Plants: poor source (0.01–0.06%)
Animal products: good source (0.1–0.8%), esp. marine (fishmeal)
Supplement: salt 0.3–0.5% of diet, or free-choice salt blocks (plain, iodized, trace mineral)

Functions

Osmotic balance (primary extracellular cation)
Na⁺/K⁺ pump: drives absorption of carbohydrates and amino acids
Transmission of nerve impulses
Nutritional wisdom: Na is the main nutrient for which animals detect deficiency and seek it out

Deficiency

Causes: lactation (Na⁺/Cl⁻ secreted in milk), rapidly growing animals on cereal-based diets, tropical conditions (sweat loss)
Symptoms: pica/salt craving, licking wood/soil/sweat, loss of appetite, decreased growth, reduced milk production, weight loss
↓ osmotic pressure → dehydration → weakness; poor growth due to reduced carb/AA absorption

Chlorine (Cl)

Functions

Regulation of osmotic pressure
HCl in gastric juice → protein digestion
Pancreatic juice, bile, intestinal secretions
Required for amylase activity

Deficiency

Deficiency only on purified diets
1978: Neo-Mull-Soy/Milk-Free infant soy formulas deficient in Cl (manufacturer forgot NaCl) → 1979: recalled by CDC
Leads to metabolic alkalosis (abnormal ↑ bicarbonate)
Reduced growth, depraved appetite, emaciation

SSulfurMost reactive macromineral

Forms in the Body

Almost all S in body is in methionine + cysteine (protein-bound) and taurine (free)
Inorganic sulfates present in small quantities
Also found in: sulfides, thiamin (B1), biotin (B7)
No RDA for sulfur in humans
Glycosaminoglycans: chondroitin sulfate (cartilage, bone, tendons, blood vessel walls); heparin sulfate (plasma membrane, immune response)

Ruminant Considerations

Ruminal microbes incorporate sulfate into S-containing amino acids
S required for optimal microbial growth and thiamin & biotin synthesis
Target N:S ratio = 10:1 in ruminants
Optimum dietary S: 0.16–0.24%
Rumen bypass methionine: methionine is the most-limiting amino acid for milk protein synthesis in dairy cows

Deficiency / Toxicity

Deficiency (ruminants): reduced appetite/weight gain, anorexia, decreased wool growth (sheep), dullness, weakness, decreased milk production
Toxicity (ruminants): high S → ruminal H₂S gas (eructated & inhaled) → polioencephalomalacia (thiamin deficiency, softening of cerebrocortical grey matter); head pressing, muscle tremors, teeth grinding, rapid death

MgMagnesium60–70% in bone

Sources

Higher in forages than grains
Cool season grasses > legumes
Lower with nitrogen fertilizers (vigorous growth dilutes Mg)
Supplements: MgO (insoluble, ~50% Mg), MgCO₃, MgCl₂ (soluble), MgSO₄ (soluble)

Functions

Structural component of bone (60–70% of body Mg; bone ash 0.5–0.7% Mg)
Required for all phosphate-transferring systems (ATP → ADP)
Enzyme activation: complexed with ATP/ADP/AMP in carbohydrate and lipid metabolism; binds mRNA to ribosomes
Activator of all reactions requiring thiamin pyrophosphate (TPP) → essential for glucose metabolism
Vasodilation (reduced blood pressure)

Deficiency — Grass Tetany

Hypomagnesemia = grass tetany / grass staggers
Mainly cattle grazing cool season grasses with high K, high N, low Na → impairs Mg absorption
Also: sudden feed changes, stress, transport
Symptoms: nervousness, hyperirritability, tremors, convulsions, facial twitching, staggering gait
Treatment: i.v. Ca + Mg solution; MgO dusted on feed/pasture; Mg lick blocks; MgSO₄ or MgCl₂ in hay/silage

Microminerals (Trace Minerals)

Overview

11 microminerals: Mn, Fe, Zn, Cu, Se, I, Cr, F, Co, Mo, B — needed in small amounts (<100 mg/day), measured in ppm (mg/kg)
Despite small amounts needed, deficiencies can be devastating (e.g., white muscle disease from Se deficiency)
Many function as metalloenzyme components or enzyme activators

FeIronHemoglobin 65%, Myoglobin 10%

Distribution

Functional (80%): hemoglobin 65%, myoglobin 10%, metalloenzymes 4%, transferrin (transport) 1%
Storage (20%): ferritin 15%, hemosiderin 5%

Sources

Green leafy vegetables
Legumes
Animal origin products

Deficiency

Baby pig anemia: most common — piglets born with limited Fe stores, sow's milk low in Fe → treated with iron dextran injection
Serum Fe <20 µg/dL = anemia
Signs: thumps, pale skin/mucous membranes, poor growth

CuCopperBody content: 1.5–2.0 ppm

Sources & Metabolism

CuSO₄, TBCC (tribasic Cu chloride), Cu-Lys (organic)
Bioavailability: nonruminants 5–30%, ruminants 1–80%
Transport: ceruloplasmin (90% of plasma Cu)
Homeostasis: metallothionein regulates Cu absorption

Functions

O₂-carrying proteins (ceruloplasmin)
Cytochrome C oxidase (electron transport chain)
Melanin formation (tyrosinase)
Connective tissue cross-linking (lysyl oxidase)

Deficiency / Diseases

Poor growth, anemia, depigmentation, nervous lesions
Menkes disease (humans): ATP7A gene mutation → Cu absorption defect → neurodegeneration
Wilson's disease (humans): ATP7B gene mutation → Cu accumulates in liver/brain

MoMolybdenumPurine catabolism enzyme

Functions

Xanthine oxidase: purine catabolism → hypoxanthine → xanthine → uric acid
Aldehyde oxidase: oxidizes aldehydes

Deficiency

Deficiency not reported under practical conditions
High Mo can antagonize Cu absorption (ruminants)

SeSeleniumFDA regulated: max 0.3 ppm added, 2.0 ppm tolerable

Sources

Soil-dependent (selenium distribution varies widely)
Selenomethionine (organic, plants)
Se-yeast / OH-selenomethionine
Injectable Bo-Se (selenium + Vitamin E)

Functions

Glutathione peroxidase: antioxidant enzyme protecting cells from oxidative damage
Thyroid hormone activation (5'-deiodinase)
Eicosanoid biosynthesis

Deficiency / Toxicity

Deficiency (<0.1 ppm): white muscle disease, mulberry heart disease, stiff lamb disease, suppressed immunity, impaired reproduction
Chronic toxicity: hair loss, appetite loss, damaged hooves, stiffness of joints
Acute toxicosis: staggering, labored breathing, pulmonary edema, prostration, ataxia, death; caused by overgrazing high-Se pastures or supplementation errors

FFluorineDental health; narrow therapeutic window

Sources & Body Distribution

Plants have limited ability to absorb F from soil
Forages: 2–20 ppm F; cereals: 1–3 ppm
Humans: primarily drinking water
Animals: bone meal, meat and bone meal
Body: 0.02–0.05% of apatite in bones and teeth; soft tissues rarely >2–4 ppm
F causes apatite crystals to be larger, harder, more resistant to acid
Hydroxyapatite + 2NaF → fluoroapatite (more acid-resistant) + 2NaOH

Functions (Dental)

1942: correlation discovered between F in water and ↓ dental caries prevalence
F in toothpaste/water: inhibits bacterial enolase (penultimate step of glycolysis) → disrupts bacterial acid production
Fluoroapatite resists demineralization by bacterial acids
0.7–1 ppm in drinking water reduces dental caries

Toxicity

1 ppm — reduces dental caries (beneficial)
2 ppm — mottled enamel (dental fluorosis)
8 ppm — osteosclerosis (↑ bone density, abnormal hardening)
110 ppm — reduced growth
>5 ppm — serious toxicosis in livestock
>1.5 ppm in humans — linked to birth defects, miscarriage, stillbirths
Chronic fluorosis: skin lesions, dental fluorosis, gingivitis; from F-contaminated forages near industrial plants (phosphate ore, aluminum, steel smelters)

IIodineHeaviest essential element; thyroid 70–80%

Distribution & Sources

Thyroid gland: 70–80% of body I
Muscle 10–20%, hide 4%, skeleton 3%, other organs 5–10%
Iodine is the heaviest element required by animals for physiological function
Sources: iodized salt (granular), iodized salt blocks

Functions

Component of thyroid hormones: T₃ (triiodothyronine) and T₄ (thyroxine)
I accounts for ~60% of molecular weight of T₃/T₄
Thyroid hormones regulate metabolism, growth, thermoregulation
5'-deiodinase converts T₄ → T₃ (more active form)
Regulation: I deficiency → ↓T₃/T₄ → hypothalamus releases TRH → pituitary releases TSH → thyroid enlarges

Deficiency

Goiter: enlarged thyroid gland from TSH overstimulation; 90% of human goiter cases
Animals born hairless with swollen thyroid gland
Prevalent in inland and mountain areas far from marine-derived I
Salt iodization has nearly eliminated deficiency in humans

MnManganeseMetalloenzyme activator; bone development

Functions

Enzyme activation as Mn²⁺ (metalloenzymes)
Phosphate transferases: gluconeogenesis, lipogenesis (FA synthesis)
Decarboxylases
Glycosyltransferases: synthesis of mucopolysaccharides and glycoproteins (cartilage, bone matrix)

Deficiency

May be promoted by high dietary Ca and P (compete for absorption)
Lack of Mn decreases bone phosphatase activity
Reduced growth
Perosis (slipped tendon) in young chickens: related to impaired cartilage formation
Chondrodysplasia in pregnant cattle: fetal abnormal bone development

CoCobaltVitamin B₁₂ component (cobalamin)

Functions

Constituent of vitamin B₁₂ (cobalamin)
Ruminants more sensitive to B₁₂ deficiency (B₁₂ required for gluconeogenesis from propionate)
Deficiency symptoms are those of vitamin B₁₂ deficiency, not cobalt per se

Sources

Most feedstuffs do NOT contain adequate Co levels
Estimated ruminant requirement: 0.20 ppm
Co-sulfate, Co-carbonate supplements
Soil deficiency primarily in Florida and east coast states; sandy soils also lack Cu and Fe
Co needed for optimal fiber digestion in rumen

Toxicity

Wide safety margin between toxicity and requirement
Toxicity unlikely under practical conditions due to low absorption rate
Poorly retained in body; excess Co is excreted

ZnZincSkin/hair/wool; keratinization; bone 30%

Distribution & Functions

Mainly in skin, hair, and wool (involved in keratinization)
Bone: 30% of total body Zn
Component of metalloenzymes:
Carbonic anhydrase (most Zn in RBCs)
Pancreatic carboxypeptidase A/B (protein digestion)
Lactate dehydrogenase (carbohydrate metabolism)
Zn critical for keratin formation → hoof health

Homeostasis

Controlled by rate of absorption; regulated by intestinal mucosa
Low Zn → CRIP (Cys-rich intestinal protein) enhances absorption
High Zn → metallothionein inhibits absorption (CRIP and metallothionein compete for Zn)
Factors decreasing Zn retention: dietary phytate, high Ca/Fe/Cu/Mo, excretion in pancreatic juice and feces

Deficiency

Decreased growth and appetite
Zn deficiency aggravated by high dietary Ca
Skin lesions: reddening, eruptions, scabs → parakeratosis
Reduced feathering (poultry)
Reduced immune function (abnormal thymus, T-cell dysfunction)
Majority of hoof problems in cattle related to Zn deficiency

Potentially Toxic Minerals

Classified as toxic because in biological systems, these minerals are always associated with negative effects. No known beneficial function at any concentration.

Aluminum

Arsenic

Cadmium

Lead

Exam 4Lectures 8–9 · Vitamins, Energy

Vitamins

Overview

Essential organic compounds required in minute concentrations; composed of C, H, O, and sometimes N, S, Co
Not synthesized in adequate amounts by body → must be supplied in the diet
Neither energy substrates nor structural components; act primarily as enzyme catalysts (coenzymes)
Fat-soluble: A, D, E, K — stored in body (increases toxicity risk)
Water-soluble: B-vitamins and C — not stored; kidney excretes excess (lower toxicity risk)
Most discovered 1913–1941; naming convention: alphabetical order of discovery

Fat-Soluble Vitamins

Vitamin ARetinol · Vision · Epithelial integrity

Forms & Sources

Retinol (preformed, animal products), retinal, retinoic acid
Provitamins: β-carotene (plant) → 2 retinol; α/γ-carotene → 1 retinol
Richest: liver, fish liver oils, egg yolk, yellow/orange plants
Stored in liver (90%) and fat; large body reserves
1 IU = 0.3 μg retinol = 0.6 μg β-carotene

7 Functions

Visual cycle (retinal + opsin → rhodopsin)
Epithelial cell differentiation (mucosal integrity)
Bone development & remodeling
Reproduction (sperm production, fetal development)
Immune function
Growth
Antioxidant (β-carotene)

Deficiency

Night blindness → xerophthalmia (dry eye) → total blindness
Epithelial keratinization → reduced disease resistance
Skin lesions, respiratory infections
Reproductive failure, birth defects
Slow growth
Cats: spondylosis (excessive bone formation around vertebrae)

Toxicity

Hypervitaminosis A: excessive supplementation over time
Bone demineralization, joint pain, fractures
Skin lesions, anorexia, hair loss
Especially toxic for cats fed all-liver diets
β-carotene non-toxic (excess → yellow skin, not converted)

Vitamin DCalciferols · Ca/P metabolism · Most toxic fat-soluble vitamin

Forms & Metabolism

D2 (ergocalciferol): plant origin, UV irradiation of ergosterol
D3 (cholecalciferol): animal origin, UV (290–315 nm) on skin → 7-dehydrocholesterol
D2/D3 → liver (25-OH-D3) → kidney (1,25-(OH)₂D3 = calcitriol, active form)
Calcitriol is the active hormone; regulated by PTH and blood Ca/P levels
Birds prefer D3 (D2 not equivalent); ruminants prefer D2

Functions

Increases Ca/P absorption from intestine
Mobilizes Ca/P from bone (with PTH)
Promotes Ca/P reabsorption by kidney
Critical for bone/teeth mineralization
Immune function, muscle function

Deficiency & Toxicity

Rickets (young): soft/deformed bones, bent legs, beaded ribs
Osteomalacia (adult): progressive demineralization
Milk fever (hypocalcemia) in dairy cows peripartum
Most toxic fat-soluble vitamin
Hypercalcemia → soft tissue calcification (organs, blood vessels)
Calcinosis: calcification of aorta and other soft tissues

Vitamin ETocopherols · Antioxidant · Least toxic fat-soluble vitamin

Forms & Sources

α, β, γ, δ-tocopherols and tocotrienols; α-tocopherol most active
1 IU = 1 mg dl-α-tocopherol acetate
Best sources: vegetable oils, wheat germ, green leafy vegetables
Stored in adipose, muscle, liver; no single storage organ
Works synergistically with selenium

Antioxidant Function

Breaks free radical chain reactions (radical → stable product)
Protects polyunsaturated fatty acids (PUFAs) in membranes
Protects red blood cells from hemolysis
Immune function enhancement
High dietary PUFA → higher vitamin E requirement

Deficiency Syndromes

White muscle disease (cattle/sheep): nutritional myopathy, bilateral symmetrical degeneration of skeletal/cardiac muscle
Mulberry heart disease (pigs): sudden death, heart lesions resembling mulberry
Stiff lamb disease (sheep): similar to white muscle disease
Pansteatitis (cats): yellow fat disease, from high unsaturated fish diet; depression, anorexia, hyperesthesia; treat with vit E 10–25 IU 2×/day for 5–7 days
Toxicity: least toxic fat-soluble; 1,000–2,000 IU/kg no adverse effects

Vitamin KKoagulation · Blood clotting · Least body storage of fat-soluble

Forms & Sources

K1 (phylloquinone): natural, green leafy vegetables
K2 (menaquinone): natural, enteric bacteria; K2 far more bioavailable than K1
K3 (menadione): synthetic, most potent/water soluble; 1 IU = 1 μg menadione
Supplemental forms: MSB, MSBC, MNB, MPB complexes
Sources: green leafy veg, eggs, liver, fish meal; enteric bacteria synthesis
Least body storage of fat-soluble vitamins

Function: Blood Coagulation

Required for synthesis of clotting Factors: II (prothrombin), VII (proconvertin), IX (Christmas factor), X (Stuart-Prower)
Name from Danish/German "Koagulationsvitamin"
Biological assay: clotting time in young chicks
Requirement affected by: bioavailability, dietary fat, antibiotics (kill K2-synthesizing bacteria), microbial synthesis (hindgut/rumen), coprophagy

Antagonists & Toxicity

Dicoumarol: in spoiled sweet clover hay; fatal hemorrhaging in cattle ("sweet clover disease")
Warfarin: synthetic dicoumarol, used as rat poison; both prevent prothrombin synthesis by liver
Toxicity: well-tolerated; pigs tolerate 110 mg/kg; young chickens 300 mg/kg

Water-Soluble Vitamins: B-Vitamins

Not stored; kidney excretes excess. Most function as coenzymes in metabolic reactions. Generally, deficiency symptoms include poor growth, diarrhea, dermatitis, and hair loss.

Thiamin (B1)TPP coenzyme · Pyruvate → Acetyl-CoA · Beriberi

Functions & Sources

Coenzyme: thiamin pyrophosphate (TPP)
Decarboxylation of α-keto acids: pyruvate → acetyl-CoA (pyruvate dehydrogenase)
α-ketoglutarate → succinyl-CoA + CO₂ (TCA cycle)
Tryptophan → niacin/NAD conversion (60 mg Trp → 1 mg niacin); cats cannot do this → higher niacin requirement
TCA, glycolysis, gluconeogenesis, amino acid metabolism, fatty acid synthesis
Sources: yeast, pork, cereal grains (whole > refined); US flour fortified with thiamin mononitrate
Unstable to UV and Maillard reactions

Deficiency

Beriberi (humans, polished rice): dry (wasting, paralysis) or wet (capillary weakening, edema)
Polyneuritis in poultry: anorexia, cardiac enlargement, muscular weakness
↑pyruvate → ↑lactic acid → muscular weakness; ↓acetyl-CoA → ↓lipogenesis
Impaired nerve function: Na⁺-K⁺ ATPase requires ATP; thiamin deficiency → ↓ATP → nerve dysfunction
Polioencephalomalacia (polio/stargazing) in ruminants: rumen environment destroys thiamin or inhibits production via thiaminase activity

Anti-thiamin & Requirements

Anti-thiamin factors: raw fish (thiaminase); bracken fern (horses); thiaminase breaks methylene bridge → greatly increased requirement
Requirement influenced by: digestible carbohydrate intake, thiaminase intake

Riboflavin (B2)FMN & FAD · Electron transport · Curled toe paralysis

Functions

Component of flavoproteins; coenzymes FMN and FAD
Oxidation-reduction reactions; electron transport chain
Conversion of retinal → retinoic acid; tryptophan → niacin
Imparts yellow color to vitamin premixes; turns urine fluorescent yellow

Sources

Synthesized by plants, yeasts, fungi, most bacteria
Cereal grains poor; occurs in all biological materials
Good sources: yeast, liver, milk, green leafy vegetables

Deficiency

Most common dietary deficiency but rarely see symptoms
General: poor growth, diarrhea, eye abnormalities, hair loss, dermatitis
Curled toe paralysis in young chickens (peripheral nerve degeneration)

Niacin (Nicotinic Acid)NAD & NADP · Pellagra · 4 D's

Functions & Sources

Active form: nicotinamide; component of NAD and NADP
Oxidation-reduction reactions; carbohydrate, lipid, amino acid metabolism
60 mg tryptophan → 1 mg niacin (12 steps, very slow)
Cats cannot convert Trp → niacin → much higher dietary niacin requirement
Animal proteins (beef, eggs, milk) = "niacin equivalents"
Corn: low niacin/Trp AND contains niacinogen (binds niacin, reduces availability)
Cereal grains contain nyacitin (80–90% available after hydrolysis)

Deficiency

Pellagra — "disease of 4 D's": Diarrhea, Dermatitis, Dementia, Death
Necklace lesions on skin; classic in corn-based diets
"Black tongue" in dogs
Poor growth, diarrhea

High-Dose / Lipid Effects

Pharmacologic doses (1,000–2,000 mg) can reverse atherosclerosis
Reduces cholesterol, TAG, VLDL, LDL
Toxicity at 1.5–6.0 g/day: skin flushing, maculopathy, acute toxic reactions

Pantothenic AcidCoA synthesis · Fatty acid metabolism · Goose-stepping in pigs

Functions

From Greek "pantothen" = "from everywhere"; quite stable
Required for synthesis of CoA (coenzyme A)
Major role in fatty acid and carbohydrate metabolism
Addition and loss of 2-carbon units (acyl group transfer)
Synthesis and oxidation of fatty acids; TCA cycle
Component of fatty acid synthase (as acyl-carrier protein)
Required for synthesis of fatty acids, cholesterol, acetylcholine

Sources

Found in most foods/feeds (name reflects widespread occurrence)
Best sources: liver (especially chicken and pork), heart, egg yolk, yeast, molasses
Also: whole grains, wheat bran, peanuts

Deficiency

Chickens most susceptible
General: poor growth, secondary diarrhea, dermatitis, hair loss
Goose-stepping gait in pigs (spastic hindlimb movement)
Nervous system disorders

Vitamin B6 (Pyridoxine)PLP coenzyme · Amino acid metabolism · Neurotransmitters

Forms & Sources

3 forms: pyridoxine, pyridoxamine, pyridoxal
Metabolically active form: pyridoxal phosphate (PLP)
Plant: pyridoxine (stable); animal: pyridoxal/pyridoxamine (less stable)
Commercial: pyridoxine HCl (very stable)
Found in virtually all foods: yeast, liver, milk, legumes, cereal grains, vegetables

Functions

>140 pyridoxal phosphate-dependent activities
Glycogen → glucose via glycogen phosphorylase (PLP)
>½ of PLP in body stored in muscle (glycogen phosphorylase)
Macronutrient metabolism: decarboxylation, transamination, racemization; amino acid catabolism, gluconeogenesis, sphingolipid synthesis
Synthesis of neurotransmitters (serotonin, epinephrine, norepinephrine), histamine, hemoglobin

Deficiency

Poor growth rate, scaling dermatitis, hyperirritability
Muscular weakness and anemia
Infertility, fetal malformations
Insulin insufficiency (reduced pancreatic synthesis)

BiotinCarboxylase enzymes · Avidin interaction · Cracked foot pads

Functions

Found as biocytin (amide complex of biotin and lysine)
Essential component of carboxylase enzymes
Carboxylation and decarboxylation reactions (most in mitochondria)
TCA cycle/gluconeogenesis: pyruvate carboxylase, propionyl-CoA carboxylase
Lipid metabolism: acetyl-CoA carboxylase
Deamination reactions

Sources & Avidin

Few foods are good sources; wide variability in bioavailability
Good sources: egg yolk, yeast, milk, kidney, liver, soybean meal
Avidin in raw egg white: strongest non-covalent bond in nature; binds biotin (ELISA assay)
Avidin-biotin complex cannot be hydrolyzed; cooking (100°C) breaks bond
Biotin in egg yolk (not bound to avidin)

Deficiency

General: poor growth, dermatitis and hair loss
Impaired lipid and energy metabolism
Cracked pads on feet (classic sign)

Folic Acid (Folate)1-carbon metabolism · DNA synthesis · Neural tube defects

Functions

From Greek "folium" (leaf); forms: DHF (dihydrofolate), THF (tetrahydrofolate)
Carrier of methyl groups (1-carbon metabolism)
Added to/removed from amino acids (His, Ser, Met), purines, polyamines
THF: essential coenzyme for thymidylic acid synthesis (thymine → DNA)
Purine synthesis (adenine and guanine)
Initiation of translation (formylmethionine)

Sources

Green leafy materials, cereal grains, extracted oilseed meals, animal protein meals
Richest: liver (beef and chicken), brewer's yeast
Mandatory US fortification since 1996

Deficiency

Reduced DNA and RNA biosynthesis → reduced cell division
Critical for women of child-bearing age (must supplement BEFORE pregnancy)
Neural tube defects: spina bifida, anencephaly, encephalocele
Anemia (impaired erythropoiesis), leucopenia
Poor growth, reduced feed intake, dermatitis/hair loss

Vitamin B12 (Cobalamin)Microbial synthesis only · Intrinsic factor · Pernicious anemia

Sources & Absorption

Deep red color; vitamers: methylcobalamin and adenosylcobalamin
Not synthesized by plants or animals; only by microorganisms (bacteria, yeasts, algae)
Cobalt required for synthesis
Sources: meat and bone meal, fish meal, whey; all B12 from microbial origin
Intrinsic factor (IF): glycoprotein secreted by gastric parietal cells; required for active transport of IF-B12 from ileum
Only essential function of stomach; diffusion ~1% without IF
Ruminants: dietary cobalt → microbial B12 synthesis (adequate)
Non-ruminants: no cobalt requirement; synthesis not adequate (except horse via hindgut)

Functions

Synthesis of labile methyl groups; B12 coenzyme for methionine synthase
Pernicious anemia: no mature RBC; caused by lack of B12 (or lack of IF)
Glucose synthesis (critical in ruminants): propionic acid → methylmalonyl-CoA (biotin) → succinyl-CoA (B12) → glucose (gluconeogenesis)
ONLY water-soluble vitamin with significant body storage

Deficiency

Ruminants: induced by low cobalt in diet
Weight loss, wasting, listlessness; mild anemia; decreased growth and feed intake
Nervous system disorders
Limited methyl group availability → increased fat deposition in liver, heart, kidneys
Critical for vegetarian/vegan diets (no animal products)
Malabsorption in dogs: inherited disorder in Border Collies, Beagles, Giant Schnauzers; oral administration not effective

Vitamin C (Ascorbic Acid)

Vitamin CCollagen synthesis · Antioxidant · Scurvy · Poultry heat stress

Dietary Requirement

Only primates (incl. humans) and guinea pigs require dietary source
Also: certain animals from India (red-vented bulbul bird, fruit bat)
These species lack L-gulonolactone oxidase (glucose → ascorbic acid pathway)
Very soluble in water; easily destroyed by oxidation, heat, air, minerals, oxidative enzymes
Stored only to limited extent; needs regular dietary provision
Essentially non-toxic; megadoses can cause kidney stones in men

Functions

Formation of collagen (catalyst): requires hydroxyproline from proline (prolyl hydroxylase); connective tissues: bone, teeth, cartilage, tendons, ligaments, skin, blood vessels
Water-soluble antioxidant
Increases absorption of nonheme iron by reducing Fe³⁺ → Fe²⁺

Deficiency: Scurvy

Fragile capillaries and hemorrhage
Swollen, bleeding, ulcerated gums
Loose teeth, skin lesions, weak bones
Anemia (2 ways): related to activation of folic acid; reduced iron absorption

Sources & Livestock Use

Citrus fruits, bell peppers (bell pepper >> strawberry > orange)
Synthetic forms relatively inexpensive
Pharmacologic dosing does NOT reduce incidence/severity of common cold
Poultry heat stress: synthetic capacity decreases in hot temps; supplementation 200–600 mg/kg improves growth, egg production, feed efficiency, egg weight, shell quality, livability

Quasi-Vitamins

Other compounds proposed as vitamins; some (like choline) fit only for certain species.

CholinePhospholipids · Fatty liver · Critical for poultry

Background & Forms

Discovered 1864, synthesized 1866; essential nutrient for humans since 1998
Quaternary saturated amine
Fed as choline chloride (animal nutrition) or choline bitartrate (human nutrition)
Natural source: phosphatidylcholine (lecithin), enriched in soy-based ingredients

Functions & Metabolism

Component of phospholipids
Structural integrity, membrane fluidity, signaling roles in cell membranes
Methionine → choline (phosphatidylcholine) in liver
Dietary requirement influenced by methionine intake
Chickens lack this methylation enzyme → much higher dietary requirement for preformed choline

Deficiency

Rare in most species; widely distributed in foods/feeds
Typically supplemented in rapidly growing agricultural animals (pigs, especially poultry)
Young birds (chicks <13 weeks) fed low-choline diets; animals fed Met-deficient diets
Symptoms: slow growth, fatty infiltration of liver, lack of coordination, low conception rates

TaurineCat essential · Retinal degeneration · Dilated cardiomyopathy

Background

Often misnamed amino acid; technically β-amino sulfonic acid
NOT incorporated into proteins

Functions & Sources

Visual acuity, neurodevelopment, Ca regulation, antioxidant, bile acid conjugation
Seafood, meat; major constituent of bile

Cats: Taurine Requirement

Cats are unable to synthesize taurine
Deficiency leads to: Central Retinal Degeneration (CRD) → blindness
Feline dilated cardiomyopathy (heart failure)
Required in all feline foods by AAFCO

Other Quasi-Vitamins

CarnitineInositolPyrroloquinoline quinoneOrotic AcidUbiquinonep-Aminobenzoic acidLipoic acidAllyl sulfur compoundsFlavonoids and polyphenolsGlucosinolatesPhytoestrogens

Take-Home Messages

Vitamins are essential nutrients required in minute concentrations; all composed of organic elements
Fat-soluble vitamins can be stored (A, D, E, K) → increases risk of toxicity; Vitamin D is most toxic
Water-soluble vitamins cannot be stored (B-vitamins, C) → kidney excretes excess; lower toxicity risk
Most B-vitamins function as coenzymes (TPP, FMN/FAD, NAD/NADP, CoA, PLP, biotin, THF, B12-coenzyme)
Key species-specific deficiencies: Cats (taurine, niacin from Trp); Ruminants (polioencephalomalacia from thiaminase, B12 from low cobalt)

Energy

Definitions & Basic Concepts

Energy = capacity to do work; measured in calories or joules
Energy is not a nutrient itself; it is derived from nutrients (carbohydrates, fats, proteins)
Ultimate currency: ATP (adenosine triphosphate)
1 calorie = heat needed to raise 1 g of water 1°C; 1 kcal = 4.185 kJ
Heat of combustion: energy released when a substance is completely oxidized (burned)

Calorimetry

Direct Calorimetry (Bomb Calorimeter)

Sample burned in O₂ atmosphere; heat measured by water temperature rise
Measures Gross Energy (GE) directly
Expensive and time-consuming; used for research

Gross Energy Values (bomb calorimeter)

Nutrient	kcal/g	kJ/g
Carbohydrates	4.1	17.2
Protein	5.7	23.9
Fats	9.4	39.3

Physiological Fuel Values (Atwater Factors)

Adjusted for digestibility and metabolic losses; used for human nutrition labeling.

4 kcal/g

Carbohydrates

Digestibility ~97%

9 kcal/g

Fat

Digestibility ~95%

4 kcal/g

Protein

Digestibility ~92%; N lost as urea

Energy Partitioning

Energy flows from gross intake through losses at each step. Each subtraction gives a more "available" form.

Gross Energy: Total energy in feed (bomb calorimeter)

− FE

Fecal Energy: Energy lost in feces (undigested feed)

Digestible Energy: GE − Fecal Energy

− UE/GasE

Urinary + Gaseous Energy: Energy lost in urine (UE) and methane/gas fermentation (GasE, especially in ruminants)

Metabolizable Energy: DE − Urinary Energy − Gaseous Energy

− HI

Heat Increment: Heat produced from digestion, absorption, metabolism (unavoidable)

Net Energy: ME − Heat Increment; energy actually available for animal use

NEm / NEp

NE for Maintenance / Production: NEm: energy for basic body maintenance; NEp: energy for growth, milk, wool, eggs

Dairy Cow Example (Mcal)

GE 78.8→DE 63.8→ME 52.3→NE 33.2

Basal Metabolic Rate & Metabolic Body Weight

Basal Metabolic Rate (BMR)

Energy expenditure at rest, fasting, thermoneutral conditions
~70% of daily energy expenditure
Organ contributions:
Liver: 27%
Brain: 19%
Skeletal muscle: 18%
Kidneys: 10%
Heart: 7%

Metabolic Body Weight (MBW)

MBW = BW⁰·⁷⁵
Accounts for surface area and metabolic scaling across species
Homeotherms: 70 kcal × MBW (kcal/day)
Poikilotherms: 18 kcal × MBW (kcal/day)
Example: 70 kg human → MBW = 70⁰·⁷⁵ ≈ 24.3 → ~1,700 kcal/day

Thermoneutral Zone (TNZ)

Temperature range within which the animal can maintain body temperature without extra energy expenditure for thermoregulation
Below TNZ (cold): extra energy needed for thermogenesis (shivering, non-shivering); less energy for production
Above TNZ (heat): evaporative cooling (panting, sweating); feed intake often drops
Optimal production occurs within the TNZ

Exam 1

Exam 2

Exam 3

Exam 4

Exam 5

Exam 5Lectures 10–11 · Nutrient Calculations, Carbohydrates

Nutrient Calculations

Systems of Measurement

English System

Pound (lb), ounce (oz), ton
Foot (ft), inch (in)
Gallon, quart, pint
1 short ton = 2,000 lbs

Metric System

Kilogram (kg), gram (g), milligram (mg)
Meter (m), millimeter (mm)
Liter (L), milliliter (mL)
1 metric tonne = 1,000 kg

Universal

Percent (%) — parts per hundred
Used in both English and metric systems
Relative proportion — dimensionless

Key English ↔ Metric Conversions

English	↔	Metric
1 pound (lb)	=	454 g = 0.454 kg
2.2 lbs	=	1 kg
1 short ton (2,000 lbs)	=	907 kg
1 metric tonne (1,000 kg)	=	2,200 lbs ≈ 1.1 short tons

Relative vs. Absolute Concentration

Relative (proportional)

Percent (%) — parts per hundred
Parts per million (ppm = mg/kg)
Parts per billion (ppb = μg/kg)
Example: "12% crude protein"

Absolute (mass per mass or volume)

g/kg, mg/kg, μg/g
Example: "0.3 mg Se per kg DM"
Specifies actual mass — not dependent on total

Dry Matter (DM) Concepts

As-Is Basis

Feed as you would find it — includes water
What the animal actually consumes
Nutrient values are "diluted" by moisture
Example: fresh pasture grass (75–80% moisture)

Dry Matter (DM) Basis

Nutrient content expressed as if all moisture were removed
Standard reference for comparing feeds
100% DM is the reference — not a real feed!
Example: hay (88–92% DM)

Conversion Formulas

% DM = 100% − % Moisture

e.g. 78% moisture → 22% DM

DM basis = as-is ÷ DM fraction

e.g. 5% CP (as-is) ÷ 0.20 = 25% CP (DM)

As-is = DM basis × DM fraction

e.g. 25% CP (DM) × 0.20 = 5% CP (as-is)

DM intake = As-is intake × DM fraction

e.g. 10 kg feed × 0.90 DM = 9 kg DM

Practice: The Lassie Problem

A 2-lb can of dog food contains 78% moisture (22% DM) and 7% crude protein (CP) on an as-is basis. A dog requires 200 g CP per kg DM consumed. How many cans per day does the dog need if it consumes 2 cans?

Step 1 — Convert 2 lbs to grams:

2 lb × 454 g/lb = 908 g as-is per can

Step 2 — Find DM in one can:

908 g × 0.22 = ~200 g DM per can

Step 3 — Convert CP to DM basis:

7% CP (as-is) ÷ 0.22 = 31.8% CP on DM basis

Step 4 — CP per can (absolute):

200 g DM × 0.318 = ~63.6 g CP per can

Key insight: Always clarify whether values are on as-is or DM basis before doing calculations!

Carbohydrates

Introduction

General formula: [C(H₂O)]n — carbon combined with water
Make up 60–90% of dry matter in plants — the dominant energy source in most animal diets
Primary energy source for simple-stomached animals; ruminants convert structural CHO to VFAs via fermentation
Virtually absent from animal tissues (except lactose in milk, glycogen in liver/muscle)

Classification by Chain Length

Monosaccharides

Single sugar unit. Cannot be hydrolyzed further. Examples: glucose, fructose, galactose, ribose.

Disaccharides

Two monosaccharide units. Examples: sucrose (glu+fru), lactose (glu+gal), maltose (glu+glu).

Oligosaccharides

3–10 units. Examples: raffinose, stachyose (found in legumes; cause flatulence).

Polysaccharides

>10 units. Examples: starch, glycogen (storage), cellulose, hemicellulose (structural).

Key Monosaccharides

Sugar	Formula	Type	Notes
Glucose	C₆H₁₂O₆	Aldohexose	Most common energy substrate; found in starch, cellulose, glycogen
Fructose	C₆H₁₂O₆	Ketohexose	Found in fruits, honey; sweeter than glucose
Galactose	C₆H₁₂O₆	Aldohexose (C-4 epimer of glucose)	Component of lactose (milk sugar)
Mannose	C₆H₁₂O₆	Aldohexose	Found in plant polysaccharides
Ribose	C₅H₁₀O₅	Aldopentose	Backbone of RNA; found in nucleotides
Xylose	C₅H₁₀O₅	Aldopentose	Major component of hemicellulose in plant cell walls
Arabinose	C₅H₁₀O₅	Aldopentose	Plant cell walls; arabinoxylan in cereal grains

Plant Carbohydrate Classification (CHO Fractions)

CHO-H (Highly fermentable)

Plant cell contents — rapidly digested

Simple sugars (sucrose, glucose, fructose)
Starch (α-1,4 and α-1,6 linked glucose)
Pectin, organic acids
Absorbed in small intestine or rapidly fermented

CHO-FR (Fermentable fiber)

Plant cell wall — fermented by gut microbes

Hemicellulose (xylans, arabinoxylans)
Fermented in hindgut / rumen → VFAs
Not absorbed directly; energy via VFA

CHO-FS (Structural/slow fiber)

Plant cell wall — slowly fermented or indigestible

Cellulose (β-1,4 linked glucose)
Digestible only by microbial cellulase
Monogastrics cannot digest; ruminants partially can

Carbohydrate Digestion & Absorption (Small Intestine)

Polysaccharides → disaccharides (via amylase, brush border enzymes) → monosaccharides → absorbed across enterocytes

Glucose & Galactose

Absorbed via SGLT1 (sodium-glucose cotransporter) — active transport driven by Na⁺ gradient

Fructose

Absorbed via GLUT5 — facilitated diffusion (no energy required, follows concentration gradient)

Exit into blood

All monosaccharides exit the enterocyte basolaterally via GLUT2 into the portal circulation

Small Intestinal Structure

Villi increase absorptive surface area
Microvilli (brush border) on enterocytes — further amplify surface area
Brush border enzymes: maltase, sucrase, lactase
Average length: ~6 m in humans

Energy Value

4 kcal/g (Atwater physiological fuel value)
Bomb calorimeter (GE): ~4.1 kcal/g
Lower energy density than fat (9 kcal/g)
CHO is the preferred energy source for most tissues (esp. brain, RBCs)