Animal Nutrition, Digestion, Feeds, and Feed Processing

Comprehensive practice flashcards covering monogastric and ruminant gastrointestinal physiology, proximate and Van Soest feed evaluation, energy and protein concentrate classification, industrial feed processing methods, forages and roughages, and mycotoxicology.

Digestion

All of the chemical and physical changes that food undergoes in the digestive tract to prepare nutrients for absorption into the body.

Prehension

The mechanism by which animals bring food into their mouths, primarily using the lips, teeth, or tongue.

Mastication

The mechanical digestion process of crushing and breaking food into smaller particles using the teeth and jaw movements.

Deglutition

The act of swallowing, which conveys food down the esophagus toward the stomach via coordinated peristalsis.

Parietal (Oxyntic) Cells

Specialized cells located in the fundic and peptic regions of the stomach that secrete hydrochloric acid ($\text{HCl}$).

Chief (Peptic) Cells

Stomach cells in the gastric pits of the fundus that synthesize and secrete proteolytic zymogens such as pepsinogen.

Proventriculus and Gizzard

The avian two-part stomach system: the glandular _______________ produces digestive acids and enzymes, while the muscular _________ grinds digesta using ingested grit.

Cholecystokinin (CCK)

A peptide hormone produced by the duodenal mucosa and brain that triggers gallbladder and pancreatic contractions, stimulates pancreatic enzyme synthesis, inhibits gastric acid secretion, and can induce satiety.

Secretin

A duodenal mucosal hormone released upon acidification or presence of peptones that stimulates bicarbonate and fluid output from the pancreas and bile system.

Indole and Skatole

Volatile end-product metabolites produced by the bacterial deamination and decarboxylation of tryptophan in the large intestine, responsible for fecal odor.

Enterokinase

An intestinal enzyme that cleaves the inactive pancreatic zymogen trypsinogen into active trypsin, which subsequently activates other peptidase precursors.

Reticulum

The cranial compartment of the ruminant forestomach characterized by an interior honeycomb lining; it traps foreign objects and works with the rumen to facilitate digesta mixing and regurgitation.

Omasum

The third ruminant compartment characterized by multiple muscular leaves ('many plies') that acts as a sieve to prevent large particles from passing, absorbs water, and takes up volatile fatty acids.

Abomasum

The 'true stomach' of ruminants, which is fully glandular and secretes hydrochloric acid and pepsin to digest microbial biomass and bypass nutrients.

Esophageal (Reticular) Groove

A muscular fold in young pre-ruminants that closes during suckling to bypass the rumen and reticulum, directing milk straight into the abomasum.

Rumination

The cyclical process of re-chewing cud in ruminants, comprising the '$4\text{ R's}$': regurgitation, remastication, reinsalivation, and redeglutition.

Volatile Fatty Acids (VFAs)

Short-chain fatty acids (primarily acetate for fat synthesis, propionate for gluconeogenesis, and butyrate for rumen wall energy) produced by microbial fermentation that serve as the main energy source for ruminants.

Reticulum Magnet

A permanent magnetic cylinder administered orally via a balling gun into the reticulum of cattle to capture ingested ferrous debris and prevent traumatic reticuloperitonitis ('hardware disease').

Eructation

The expulsion of microbial fermentation gases (chiefly $\text{CO}_2$ and $\text{CH}_4$) from the rumen via silent esophagus-trachea contractions at rates up to $600\,\text{L/day}$.

Frothy Bloat (Primary Bloat)

A severe digestive disorder in ruminants caused by gas becoming entrapped within a stable viscous foam after consuming lush legumes like alfalfa, blocking eructation at the cardia.

Acute Rumen Acidosis

A life-threatening clinical state occurring when excessive consumption of rapidly fermentable carbohydrates causes lactic acid accumulation, plunging rumen $\text{pH}$ below $5.0$.

Subacute Ruminal Acidosis (SARA)

A chronic metabolic condition characterized by intermittent bouts where rumen $\text{pH}$ drops to between $5.2$ and $5.6$ due to accumulated volatile fatty acids, causing erratic intake and depressed milk fat.

Proximate Analysis

A traditional feed analysis system developed in 1865 that partitions a sample into water, crude protein, ether extract, crude fiber, ash, and nitrogen-free extract.

Crude Protein (CP)

An estimate of total protein and non-protein nitrogen in feedstuff calculated analytically by multiplying total Kjeldahl nitrogen by the factor $6.25$.

Ether Extract (EE)

The crude fat component of a feed determined by refluxing a dried sample with petroleum ether to extract lipids, true fats, fatty acids, and waxes.

Crude Fiber (CF)

The residue remaining after consecutive boiling in dilute acid and dilute alkali, representing the less-digestible fibrous carbohydrates (primarily cellulose and lignin).

Ash

The inorganic mineral residue obtained by incinerating feed samples in a muffle furnace at $600^\circ\text{C}$.

Nitrogen-Free Extract (NFE)

The readily digestible, non-fibrous carbohydrate fraction of feed calculated by the difference: $\text{NFE} = 100 - (\%\text{Water} + \%\text{CP} + \%\text{EE} + \%\text{CF} + \%\text{Ash})$.

Total Digestible Nutrients (TDN)

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

Neutral Detergent Fiber (NDF)

The insoluble residue remaining after neutral detergent extraction consisting of cell wall components (cellulose, hemicellulose, lignin, and silica) that inversely predicts voluntary feed intake.

Acid Detergent Fiber (ADF)

The fibrous fraction remaining after boiling in acid detergent solution consisting primarily of cellulose and lignin that inversely correlates with forage digestibility.

Non-Fiber Carbohydrate (NFC)

Highly digestible cellular carbohydrates (starches and sugars) calculated from Van Soest fiber fractions as: $\text{NFC} = 100 - (\%\text{NDF} + \%\text{CP} + \%\text{CFat} + \%\text{Ash})$.

Near Infrared Reflectance Spectroscopy (NIR)

A rapid, non-destructive analytical method that quantifies feed chemical constituents by measuring the reflection of near-infrared radiation calibrated against wet-chemistry data.

Energy Concentrates

Feeds containing high concentrations of digestible energy with less than $20\%\,\text{CP}$ and less than $18\%\,\text{CF}$, such as cereal grains.

Zein

The primary endosperm storage protein in corn kernels that comprises roughly half of corn protein and is characteristically deficient in lysine and tryptophan.

Opaque-2 Corn

A genetically modified or selectively bred mutant corn cultivar with reduced zein content that provides significantly elevated concentrations of lysine and tryptophan.

Tannins

Polyphenolic compounds found in 'bird-resistant' sorghum varieties that precipitate proteins, impart an astringent taste, and depress palatability and digestive efficiency.

Triticale

A synthetic hybrid cereal grain created by crossing wheat with rye to blend cold and drought hardiness with improved protein quality.

Cassava

A high-yielding tropical root crop rich in digestible non-fiber carbohydrates whose fresh state contains toxic cyanogenic glycosides (prussic acid) requiring heat treatment before feeding.

Phytic Acid (Phytin)

An organic storage compound in plant seeds that binds approximately half of plant phosphorus, rendering it largely unavailable to monogastric animals lacking endogenous phytase.

Soybean Meal (SBM)

The predominant plant protein supplement in animal nutrition, containing $44\%$ to $48.5\%\,\text{CP}$ with an exceptional concentration of lysine ($3.0-3.5\%$).

Trypsin Inhibitor

A heat-labile antinutritional factor present in raw soybeans that binds and inactivates digestive proteases, causing reduced protein digestibility and pancreatic hypertrophy.

Gossypol

A toxic polyphenolic yellow pigment in cottonseed that causes cardiac damage, pneumonia-like symptoms, and green yolk discoloration in eggs; its toxic free form can be neutralized $1:1$ with ferrous sulfate.

Canola

A genetically improved cultivar of rapeseed bred specifically to possess low levels of erucic acid and goitrogenic glucosinolates.

Meat Meal

The dry-rendered mammalian tissue product free from blood, hair, horn, hide, manure, and stomach contents; when its phosphorus level exceeds $4.4\%$, it is classified as meat and bone meal.

Non-Protein Nitrogen (NPN)

Nitrogenous compounds that are not true proteins (such as urea, ammonium salts, and biuret) which rumen microbes utilize as ammonia precursors to synthesize microbial protein.

Arthrospira platensis

A cultivated freshwater blue-green microalgae with roughly $50\%\,\text{CP}$ capable of yielding approximately ten times as much protein per unit land area as soybeans.

Corn Gluten Meal

A high-protein ($41-60\%\,\text{CP}$) dried residue obtained from wet corn milling after removal of starch and germ, known for its slow rumen degradation rate.

Corn Gluten Feed

A bulky wet-milling co-product containing approximately $18\%\,\text{CP}$ and $8\%\,\text{CF}$ that undergoes relatively rapid fermentation in the rumen.

Hominy Feed

A palatable, energy-dense co-product of dry corn milling consisting of the corn bran, germ, and part of the starchy endosperm containing approximately $10\%\,\text{CP}$.

Wheat Middlings

A milling by-product consisting of fine particles of wheat bran, germ, and endosperm containing roughly $16.5\%\,\text{CP}$ and providing $91\%$ of the energy value of corn.

Distillers Dried Grains with Solubles (DDGS)

The primary nutrient-dense by-product of dry-grind corn ethanol fuel production, rich in crude protein, fiber, and phosphorus.

Heat Increment of Fat

The lower metabolic heat production associated with dietary fat digestion and metabolism compared to carbohydrates, making supplemental fats especially beneficial in hot weather.

Whole Cottonseed

A distinct 'triple-$20$' feedstuff providing roughly $20\%\,\text{CP}$, $20\%\,\text{fat}$, and $20\%\,\text{CF}$, supplying concentrated energy and effective forage fiber for ruminants.

Rollermill

A cold feed-processing device that flattens and cracks grain kernels between pairs of smooth or corrugated revolving cylinders, producing minimal fines and dust.

Hammermill

A feed mill that shatters whole grain kernels and coarse roughages using rotating steel hammers until the particles pass through a calibrated sizing screen.

Reconstitution

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

Steam-Flaked Grains

A hot-processing method where grains are steamed for $40-80\,\text{minutes}$ to reach $18-20\%$ moisture and then passed through tight rollers to generate thin flakes that optimize starch gelatinization.

Esophagogastric Ulcers

Erosions and ulcerations in the pars esophagea of swine stomachs caused by excessively fine particle grinding ($0.16\,\text{cm}$ screens) and high fluid dynamics.

Continuous Flow Mixers

Automated feed mixers that simultaneously proportion, convey, and blend ingredients continuously, common in commercial swine and poultry facilities that handle non-bulky diets.

Mycotoxins

Low-molecular-weight, toxic secondary fungal metabolites synthesized by filamentous molds in response to environmental or plant stress.

DON

A trichothecene mycotoxin produced by Fusarium graminearum that inhibits eukaryotic protein synthesis, causing acute feed refusal and emesis in swine.

Zearalenone (ZEA)

An estrogenic mycotoxin produced by Fusarium graminearum that mimics $17\beta\text{-estradiol}$ and binds estrogen receptors, triggering vulvovaginitis and prolapse in prepubertal gilts.

Aflatoxin B1 (AFB1)

A potent hepatotoxic and carcinogenic metabolite produced by Aspergillus flavus and Aspergillus parasiticus that binds host DNA after cytochrome P450 hepatic bioactivation.

Aflatoxin M1 (AFM1)

The hydroxylated metabolite of aflatoxin B1 excreted into bovine milk, legally restricted by the FDA to a maximum threshold of $0.5\,\text{ppb}$.

Fumonisin

A mycotoxin synthesized by Fusarium moniliforme that disrupts sphingolipid biosynthesis via ceramide synthase inhibition, targeting the central nervous system and vascular endothelium.

Equine Leukoencephalomalacia (ELEM)

A fatal neurotoxic syndrome in horses ('blind staggers') caused by fumonisin ingestion, resulting in liquefactive necrosis of cerebral white matter.

Porcine Pulmonary Edema (PPE)

An acute respiratory condition in pigs characterized by severe transudation of fluid into the lungs, caused by fumonisin toxicity.

Sclerotia (Ergot Bodies)

Dark, compact fungal resting structures formed by Claviceps purpurea that replace kernel ovaries in flowering cereals such as rye.

Gangrenous Ergotism ('Fescue Foot' Syndrome)

A clinical condition induced by ergot alkaloids or tall fescue endophytes causing severe peripheral vasoconstriction, leading to dry gangrene and sloughing of hooves, ears, and tails.

Hydrated Sodium Calcium Aluminosilicate (HSCAS)

An inorganic clay-based feed additive that selectively adsorbs planar polar mycotoxins like aflatoxin B1 via interlayer cationic interactions.

Forage / Roughage

Bulky vegetative feedstuffs containing $20\%$ or more crude fiber on a $90\%\,\text{DM}$ basis ($18\%\,\text{CF}$ on a $100\%\,\text{DM}$ basis).

Big Bluestem

A palatable, perennial warm-season tall prairie grass native to the Great Plains and Midwest that provides high-yielding summer grazing and hay.

Sweet Clover Disease

A fatal hemorrhagic disorder occurring when naturally occurring plant coumarin in sweet clover is converted by molds into dicoumarol, an anticoagulant that disrupts blood clotting.

Birdsfoot Trefoil

A perennial forage legume with a high tannin profile that prevents ruminal frothing and bloat, tolerating less fertile and acidic soils.

Silage

A preserved moist forage produced through controlled anaerobic lactic acid fermentation at $50-70\%$ moisture after thorough packing to exclude oxygen.