Animal Nutrition: Digestion, Feed Evaluation, Feedstuffs, Processing, and Mycotoxins

Comprehensive practice vocabulary flashcards covering monogastric and ruminant digestive physiology, feedstuff proximate and detergent analysis, energy and protein concentrates, by-products, forage preservation, feed processing methods, and agricultural mycotoxins.

Prehension

The mechanism by which animals grasp and convey feed into their mouths using their lips, teeth, or tongue.

Mastication

The mechanical breakdown of food in the mouth by chewing, which reduces particle size and increases surface area for digestive enzymes.

Deglutition

The act of swallowing, which propels food through the esophagus to the stomach or crop via wave-like peristaltic muscular contractions.

Crop

An expanded pouch of the esophagus in poultry that temporarily stores and softens food before it continues down the digestive tract.

Proventriculus

The glandular stomach of avian species that initiates chemical digestion by secreting hydrochloric acid ($\text{HCl}$) and gastric enzymes.

Gizzard (Ventriculus)

A thick, muscular organ in poultry that physically grinds food into smaller particles, often aided by ingested stones or grit.

Rumen

The largest compartment of the ruminant stomach, functioning as an anaerobic microbial fermentation chamber lined with nutrient-absorbing papillae.

Reticulum

The cranial ruminant stomach compartment characterized by a honeycomb lining that aids in mixing, rumination, and trapping heavy foreign debris.

Omasum

The third ruminant stomach compartment containing numerous broad muscular folds ('manyplies') that absorb water, volatile fatty acids, and minerals.

Abomasum

The glandular 'true stomach' of ruminants, which secretes hydrochloric acid ($\text{HCl}$) and pepsin to digest feed and microbial protein.

Esophageal Groove

A muscular fold in suckling young ruminants that shunts milk directly from the esophagus to the abomasum, bypassing the undeveloped rumen.

Rumination

The coordinated process in ruminants consisting of regurgitation, remastication, reinsalivation, and redeglutition of coarse fibrous digesta.

Eructation

The elimination of microbial fermentation gases ($\text{CO}_2$ and $\text{CH}_4$) from the reticulorumen via silent belching.

Volatile Fatty Acids (VFAs)

The primary energy source for ruminants produced by microbial fermentation of carbohydrates, consisting predominantly of acetate, propionate, and butyrate.

Hardware Disease

Traumatic reticuloperitonitis caused when sharp metallic foreign objects lodged in the reticulum puncture the reticular wall and diaphragm; prevented by placing a cow magnet in the reticulum.

Rumen Acidosis

A metabolic disorder caused by rapid consumption of readily fermentable grains or inadequate fiber, resulting in an accumulation of acids and a drop in rumen $\text{pH}$ below $5.0$ (acute) or between $5.2\text{--}5.6$ (subacute).

Cecum

A blind sac situated at the junction of the small and large intestines that acts as the primary microbial fermentation site in hindgut fermenters such as horses and rabbits.

Gastric Chief Cells

Specialized secretory cells in the peptic and fundic gastric pits that synthesize and release zymogenic proteolytic enzymes such as pepsinogen.

Parietal Cells

Oxyntic cells within the gastric glands that secrete hydrochloric acid ($\text{HCl}$), which lowers stomach $\text{pH}$ and activates pepsinogen to pepsin.

Bile

An alkaline hepatic secretion stored in the gallbladder that emulsifies dietary lipids and forms micelles to facilitate fat absorption in the small intestine.

Cholecystokinin (CCK)

A peptide hormone secreted by the duodenal mucosa in response to fatty acids and peptones that stimulates pancreatic enzyme release and gallbladder contraction.

Rennin

A gastric enzyme found in the abomasum of young ruminants that coagulates milk casein into calcium caseinate to prolong its retention time in the stomach.

Proximate Analysis

A quantitative chemical scheme developed in 1865 that partitions feedstuffs into water, crude protein, ether extract, crude fiber, ash, and nitrogen-free extract.

Crude Protein (CP)

An estimate of total protein based on total nitrogen measured by the Kjeldahl method, calculated as: $\text{CP}\% = \text{N}\% \times 6.25$.

Ether Extract (EE)

A laboratory procedure that measures the crude fat content of a dry feed sample by dissolving lipids in boiling ether.

Crude Fiber (CF)

The organic residue containing cellulose, hemicellulose, and lignin left after boiling an ether-extracted feed sample sequentially in dilute acid and dilute alkali.

Ash

The non-combustible inorganic mineral matter remaining after incinerating a feedstuff sample in a furnace at $600^\circ\text{C}$.

Nitrogen-Free Extract (NFE)

The readily available soluble carbohydrate fraction calculated by difference: $\text{NFE}\% = 100 - (\%\text{Water} + \%\text{CP} + \%\text{EE} + \%\text{CF} + \%\text{Ash})$.

Total Digestible Nutrients (TDN)

An energy index on a carbohydrate-equivalent basis computed as: $\text{TDN} = (\%\text{CP} \times \text{Dig.}) + (\%\text{EE} \times \text{Dig.} \times 2.25) + (\%\text{CF} \times \text{Dig.}) + (\%\text{NFE} \times \text{Dig.})$.

Neutral Detergent Fiber (NDF)

The cell wall fraction consisting of cellulose, hemicellulose, and lignin obtained by boiling in neutral detergent; higher values reduce voluntary dry matter intake.

Acid Detergent Fiber (ADF)

The fibrous residue of cellulose and lignin left after boiling a sample in acid detergent solution; inversely correlated with forage digestibility.

Near Infrared Spectroscopy (NIRS)

A rapid instrumental evaluation technique that measures reflected infrared radiation from ground feed samples, calibrated against wet chemistry to predict nutrient composition.

Zein

The primary endosperm storage prolamin protein found in corn kernels, accounting for roughly half of the total corn protein.

Opaque-2 Corn

A mutant corn cultivar containing reduced zein that yields elevated concentrations of essential lysine and tryptophan, improving protein quality.

Tannins

Polyphenolic compounds found in bird-resistant grain sorghum varieties that bind and precipitate proteins, reducing palatability and digestiblity.

Oat Groats

Dehulled oat kernels that provide a high feeding value comparable or superior to corn ($84\%\,\text{TDN}$, $16\%\,\text{CP}$).

Cassava

A high-yielding tropical root crop rich in readily available carbohydrates ($65\%\,\text{water}$, $1\text{--}2\%\,\text{CP}$) that requires heat processing to eliminate toxic prussic acid.

Soybean Meal (SBM)

The most widely fed plant protein concentrate ($44\text{--}48.5\%\,\text{CP}$), recognized for possessing the highest lysine concentration ($3.0\text{--}3.5\%$) of any plant source.

Trypsin Inhibitor

A heat-labile antinutritional protein present in raw soybeans that blocks proteolytic activity of trypsin; inactivated by proper toasting.

Genistin

A phytoestrogenic compound found naturally in soybeans that possesses growth-promoting properties but can be inactivated by heat.

Gossypol

A yellow polyphenolic pigment found in cottonseed meal that causes cardiac problems and pneumonia-like symptoms in nonruminants, along with olive-green egg yolks.

Canola

An improved cultivar of rapeseed characterized by low levels of erucic acid and glucosinolates, containing approximately $10\%$ omega-3 and $16\%$ omega-6 fatty acids.

Meat Meal

A dry-rendered protein product derived from mammal tissues excluding blood, hair, hoof, horn, hide trimmings, manure, and stomach contents; banned from ruminant rations in the US due to BSE.

Tankage

A rendered animal protein by-product that may contain blood meal, gut, and tendons alongside bone and muscle tissues, used predominantly in swine feeding.

Non-Protein Nitrogen (NPN)

Nitrogen-containing compounds not in polypeptide form (such as urea with $45\%\,\text{N}$ and $281\%\,\text{CP}$ equivalent) that rumen microbes utilize to build microbial protein.

Corn Gluten Meal

A high-protein wet-milling residue ($41\text{--}60\%\,\text{CP}$) that degrades slowly in the rumen and is limited to $\le 15\%$ or $5\,\text{lb/day}$ in dairy cattle diets to maintain palatability.

Corn Gluten Feed

A bulky co-product of wet corn milling containing bran, germ, and gluten ($18\%\,\text{CP}$, $83\%\,\text{TDN}$) that degrades rapidly in the rumen.

Distillers Dried Grains with Solubles (DDGS)

A high-energy, high-protein residue ($25\%\,\text{CP}$, $82\%\,\text{TDN}$) produced by fuel-ethanol grain fermentation; inclusion must be managed to avoid phosphorus and protein excesses.

Heat Increment

The heat generated during the digestion and metabolism of feed; dietary fats have a lower heat increment than carbohydrates, making fat feeding advantageous during heat stress.

Whole Cottonseed

A unique 'triple 20' feed ingredient for ruminants containing approximately $20\%$ crude protein, $20\%$ fat, and $20\%$ crude fiber.

Legumes

Forage plants (such as alfalfa and clovers) that fix atmospheric nitrogen via symbiotic rhizobia in root nodules, producing feeds higher in crude protein and calcium than grasses.

Silage

High-moisture green forage ($50\text{--}70\%\,\text{moisture}$) preserved anaerobically in silos through bacterial fermentation producing lactic and organic acids.

Rollermill

A cold-processing machine that compresses whole grain kernels between smooth or corrugated revolving cylinders to produce cracked, rolled, or flaked feed with minimal dust.

Hammermill

A feed grinding mill that utilizes rotating steel bars (hammers) to shatter feed particles against a screen whose pore size controls the final fineness.

Reconstitution

A cold grain processing method in which water is added to mature dry grain to reach $25\text{--}30\%$ moisture, followed by anaerobic storage in an oxygen-limiting silo for $14\text{--}21\,\text{days}$.

Steam-Flaking

A hot-processing method where grain is exposed to low-pressure steam for $30\text{--}60\,\text{minutes}$ to reach $18\text{--}20\%$ moisture, then rolled into flat flakes to gelatinize starch granules.

Pelleting

A hot-processing method that forces ground, steamed mash through a steel die, preventing animal ingredient sorting and reducing feed waste.

Mycotoxins

Low-molecular-weight secondary toxic metabolites synthesized by filamentous molds in response to environmental stress, which persist long after the mold itself has died.

Deoxynivalenol (DON / Vomitoxin)

A trichothecene mycotoxin produced by Fusarium graminearum that inhibits eukaryotic protein synthesis, leading to feed refusal and emesis in swine at levels as low as $1\text{--}5\,\text{ppm}$.

Zearalenone (ZEA)

An estrogenic mycotoxin produced by Fusarium graminearum that mimics $17\beta\text{-estradiol}$ and binds estrogen receptors, inducing vulvovaginitis, prolapse, and embryonic mortality in swine.

Aflatoxin

A carcinogenic hepatotoxin produced by Aspergillus flavus; consumed aflatoxin $\text{B}_1$ is metabolized by dairy cattle and excreted in milk as aflatoxin $\text{M}_1$ (regulated to $\le 20\,\text{ppb}$ in feed and $\le 0.5\,\text{ppb}$ in fluid milk).

Fumonisin

A mycotoxin produced by Fusarium moniliforme that disrupts sphingolipid synthesis, causing Equine Leukoencephalomalacia (ELEM / 'blind staggers') in horses and Porcine Pulmonary Edema (PPE) in pigs.

Ergotism

A toxic condition caused by ingesting sclerotia of Claviceps purpurea on rye or grains, producing vasoconstriction that leads to sloughing of hooves and ears (gangrenous ergotism) and impaired cooling (summer slump).

Enzymatic Biotransformation

A mycotoxin mitigation strategy that employs specific enzymes (such as deoxynivalenase) to cleave toxic functional groups into non-toxic metabolites directly inside the GI tract.