Digestive Anatomy Flashcards
What is nutrition?
the process by which an animal takes and utilizes food substances
What is a nutrient?
any chemical element or compound in the diet that supports normal life processes
What are the nutrient categories?
- vitamins
- minerals
- water
- protein
- lipids
- carbohydrates
What are the required nutrients?
- water
- protein
- minerals
- vitamins
- energy (composed of lipids and carbs)
What are the 3 functions of a nutrient?
- structural role
- energy source
- regulation
Whats an example of a nutrient performing a structural role?
lipid bilayer, minerals used for bone health
Whats an example of a nutrient performing a energy role?
cells need ATP which they get by breaking down carbs and lipids
Whats an example of a nutrient regulating?
vitamins regulate enzyme activity or function in gene transcription
What is feedstuff?
any material used for feed (individual components)
What is a diet?
mixture of feedstuffs that supplies nutrients to the animal
What is a ration?
daily allowance/amount of feed provided to an animal
What is a meal?
feed thats consumed by an animal on a regular basis
What is feeding behavior?
what material the animal is consuming
Carnivorous Feeding Behavior
adapted to consuming meat based diets/feedstuffs
-simple, short digestive tract
ex: cats
Omnivorous Feeding Behavior
adapted to consuming a combination of plant & meat based food stuffs
-simple, longer digestive tracts
ex: dogs, chickens, pigs
Herbivorous Feeding Behavior
adapted to consuming plant material
-most complex digestive tracts bc of microbial fermentation
ex: cows, horses, sheep, goats, rabbits, rodents
What are the ruminant feeding strategies?
1: Concentrate selectors
2: Bulk and Roughage eaters
3: Intermediate feeders
Concentrate selectors
select the more nutrious, lower fiber parts of plants
-less microbial fermentation so smaller rumens
ex: deer, giraffes
Bulk and roughage eaters
consume large quantities of high fiber material
-large rumens
ex: cows
Intermediate feeders
can adapt to either a concentrate selector or bulk & rougher
Mouth
-prehension
-mastication
-salivation
-formation of bolus
-swallowing
prehension
obtaining food (using lips, tongue, teeth)
mastication
mechanical breakdown of food (teeth)
salivation
-begins the breakdown of starch
-moistens food
-kills microbes
esophagus
transports food bolus to the stomach
stomach
secretion of digestive enzymes enzymes/ HCL to begin chemical digestion
small intestine
-chyme/digesta enters from the stomach
-pancreas secretes digestive enzymes into duodenum
-chemical digestion continues
-absorption of nutrients occur
What does the duodenum secrete?
cholecystokinin
What does Cholecystokinin do?
acts on pancreas to to secrete digestive enzymes and the gallbladder to secrete bile into duodenum
What is the surface of the SI?
epithelial tissue
-epithelial cells/ villi
-microvilli
-brush border
Whats a villi (projection) consist of?
simple columnar epithelial cells are arranged into villi
Where are microvilli (tiny projections) found?
apical surface of the epithelial cell
What are glycoalyx?
mesh like projections on top of microvilli
What makes up the brush border? What happens there?
both the glycoalyx and microvilli
this is where digestion ends and absorption starts
What are the three parts of the large intestine?
- colon
- cecum
- rectum
What happens in the colon?
water absorption
What does the cecum deal with?
microbial fermentation
What happens in the rectum?
formation of feces
(which gets excreted through the anus)
What does the crop do?
stores food and moistens food
What does the proventriculus?
beginning of chemical digestion
What does the gizzard do?
mastication/mechanical digestion
What happens in the pair of ceca?
microbial fermentation
Whats the cloaca do?
common opening for digestive, reproductive, & urinary tracts
Whats the vent?
exterior opening
In a ruminant the esophagus empties into the
reticulo-rumen junction
What happens in the reticulum?
traps foreign material
Whats happens in the rumen?
- microbial fermentation
- produces volatile fatty acids that are absorbed through the rumen wall
What does the omasum do?
filtration by particle size
What happens in the abomasum?
chemical digestion
What are the advantages of a ruminant compared to monogastrics?
-utilization of fibrous foods
-microbes produce protein from ammonia & carbon sources
-microbes produce all B vitamin & vitamin K
What are the disadvantages of a ruminant compared to monogastrics?
-energy loess due to heat & gas production
-loss in protein quality due to synthesis of microbial protein
protein quality in ruminant
high quality is a waste bc the microbes change the structure of the amino acids
Foregut fermenters
-have stomach compartment where microbial fermentation occurs
-do not have stomach compartments
ex: hippo, sloths
Colon fermenters
majority of microbial fermentation occurs in enlarged colon
ex: horses
Cecal fermenters
majority of microbial fermentation occurs in enlarged cecum
ex: guina pigs, rabbits
Cecal fermenters have 2 types of feces
- hard pellets (normal)
- soft pellets: result from contractions of cecum consumed directly from anus
Whats coprophagy?
eating feces
What are the advantages of hindgut compared to ruminator?
-better adapted to high fiber, low quality diets
-rate of passage is not regulated by omasum
-higher rate of passage that allows for higher consumption
What are the disadvantages of a hindgut compared to ruminants?
-nutrients provided from fermentation are less available
-microbes get less nutritious substance for fermentation
Evaluating feeds: What do we need to know in order to efficiently utilize feeds?
-nutrition composition
-digestibility
-dry matter/as fed
-cost
-presence of toxins/ inhibitors
Feedstuff sampling
values of nutrient content are of no practical use if the sample tested is not representative of the feedstuff as it is fed to animals
Sampling hay
use hay probe which bores into bale of hay
-do 10-20 times
Pasture sampling
using 1ft by 1ft square & cut to grazing height
-do 10-20 times
Grain test
use grain probe for 10-20 samples
Feed microscopy
checks for contamination
used for regulatory purposes
Proximate analysis of feeds
standard system of chemical methods of feed analysis
Dry matter
drying feed sample to constant weight
-getting a dry sample allows you to measure amount of water in sample
Nutrient concentrations are
always higher on a DM basis
Crude protein
estimated by measuring nitrogen content of feed multiplied by factor of 6.25
-estimates protein composition through measuring nitrogen
Ether extract
crude fat estimate
-extract fat from sample with ethyl ether
-will extract all facts in sample, including waxes which are not digestible
Ash
measures inorganic portions (minerals)
-quantitive measure only
Crude fiber
not a reliable method and not very accurate
-estimates indigestible portion
NDF
-neutral detergent fiber
-uses a neutral detergent to solubilize cell contents
-leaves hemicellulose, cellulose, and lignin
(not digestable in monogastrics)
ADF
-acid detergent fiber
-uses an acid detergent to solubilize hemicellulose
-leaves cellulose and lignin (true fibrous components)
Nitrogen-free extract
estimates available carbohydrates
-a calculated value
NFE = 100 - (water + CP+ CF+ EE+ ash)
Estimating the energy content of feeds
total digestable nutrients (TDN)
sums all fractions of feed that are digestible
Determination of specific nutrients
proximate analysis gives general indication of nutrient content
-can measure individual amino acids, minerals
Energy content of feed is determined by what?
a bomb calorimeter
-tells us nothing about how energy can be used by an animal
What is digestible energy?
gross energy- fecal energy
-how much energy is digested and absorbed
What is metabolizable energy?
digestible energy - urine energy - gas energy
-how much is available for cells to use for metabolsim
What is net energy?
metabolizable energy - heat increment
-how much is available minus all loses and the expense of use of energy
Net energy options
-production
-maintenance
Assessing digestabilibty options
-total collections in metabolism crate
-using collection bags
-nylon bags (ruminants)
-using fecal marker
-illeal digestibility
*methods yield apparent digestibility not true digestibility
total collections in metabolism crate
feed the animal a known amount of the feedstuff then collect all the feces
-measure the nutrient content of the feedstuff & feces
-calculate % digestibility
using collection bags
feed animal feedstuff & collect feces in bags attached to the animal
-measure nutrient content of feedstuff & feces
-% digestibility (for each individual nutrient)
Nylon bags
put feedstuff in bag and insert bag into rumen
-remove bag over set amount of time
-measure nutrient concentrations of the feedstuff vs what is left in the bag to determine rumen digestibility
using fecal markers
add known concentration of an indigestible marker to the feed
-collect feces when marker appears in the feces
-compare nutrient concentration to fecal marker concentration
Illeal digestibility
feed animal
collect contents of the ileum to determine digestibility
true digestibility
accounts for endogenous losses throughout the digestive tract
-measure apparent digestibility & then use a correction factor that is species specific
Feed manufacturing
-process of converting raw materials into balanced diets
-produced in feed mills
-usually pelleted or meal type feed
Specialty feeds
horse, rabbit, llama, pet foods, calf milk replacers, calf growers rations
Modern feed mills are
computer controlled
Least Cost Rations
-select lowest cost feedstuffs
-feedstuffs that make up the ration will change overtime depending on the costs of feedstuff
Association of American Feed Control Officials
-set standards for quality and safety of animal feed and pet food
-establishes ingredient definitions
-not a regulatory organization
FDA
sets and enforces animal feed regulation
Feed label information required by law
-net weight
-product name, brand name
-guaranteed analysis
-common name of ingredients
-name and mailing of address of manufacturer
-directions for use
-precautionary statements for safe use
-nutritional adequacy statement
-species the food is for
Guaranteed analysis
required to have:
-min % crude protein
-min % crude fat
-max % crude fiber
-max % moisture
*expressed on an as fed basis
labels without maximum % moisture are assumed to be air dried
10% moisture
90% DM
Limitations of information on feed tag
-no info regarding protein quality
-digestible or metabolizable energy value is not known
use of drugs in fed is regulated by the FDA
-degree of regulation based on potential risk to humans from drug residues
-all drugs placed into categories based on risks
feed mixing
much feed manufactured on farms as opposed to commercial feed mills
feed mixing equipment
-raw materials ground
-efficiency of mixing influenced by order of addition of ingredients
how to mix feeds
-first add ingredients that make up majority of diet
-next add liquids slowly
-then add ingredient that make up less than 2.5% of fat
-mix for 15-20 mins
Pelleting
forcing mixed feed ingredients through a pellet pie
Advantages of pelleted feeds
-increases bulk density
-increases feed intake
-prevents sorting
-reduced dust
What’s the biggest concern with pellet quality?
crumbling
Feed is preconditioned with steam before pelleting
activates functional properties in feedstuffs allowing pellet binding
-can add pellet binders to hold pellets together
What has good functional properties?
wheat gluten
What has bad functional properties?
corn, sorghum, rice, oats
True of false: rarely feed whole grains or seeds
true
other processing methods
-grinding in hammermill
-dry or steam rolling
-flaking
-popping
-micronized grains
-tempering
-extrusion
feed efficiency
represents how well an animal can convert feed to product
-the closer the feed efficiency is to 1, the more efficient the animal is at converting feed to product
*product output/ feed input
feed conversion factors
amount of feed: amount of product
feeding trials
feed intake measurements
-have animals in pens
-feed each pen a known amount of feed
-next day, measure feed refusal
-difference b/w what was fed vs refusal is daily FI
Maximum feed intake can only be achieved w/
access to free choice water
(separate and access at all times)
meanwhile Ad libitum is not separate
What feed properties may affect feed intake?
-palatability
-energy
-protein/amino acid concentration
-forage composition
others: temperature, pregnancy, conditioning, body size, smell, fatigue
Palatability
taste, olfaction, texture
Feed preference tests can be performed
-2 different feeds on scales
-give animal access to both feeds at the same time
-animal eats more of what the animal prefers
If feeds are sufficiently palatable, dietary energy concentration will
control voluntary FI
-animals will eat to meet their energy requirements
distension feedback
-stomach distends as it fills with food
-receptors on stomach wall will send signals to satiety centers in brain to stop eating
With a low energy/fibrous diet
the stomach fills quickly
high energy diets
do not provide as much distension feedback as low energy diets
Chemostatic feedback
increases in blood metabolites will signal to satiety centers to stop eating
-glucose, VFA
What is rumen fill/distension feedback affected by:
-NDF
-water content
NDF
higher NDF, the more space it will take up in rumen causing distension feedback
Water content
higher water content of forage, the bulkier the forage will be causing distension on feedback
What is feed intake affected by in monogastrics
essential amino acids
What is feed intake affected by in ruminants
-bypass protein (bypasses microbial fermentation) : increases FI
-nitrogen: select feeds with higher N content
Environmental temperature affects on feed intake
FI increases as temp decreases
Comfort zone of an animal
range of temperatures where metabolism is at a min
When temps go below comfort zone,
feed intake increases as metabolism increases to maintain body temp
Heat increment of feedstuff
extra heat produced due to the metabolism of a nutrient
-protein has the highest
Reproduction FI
-decrease in FI during late gestation
-increase in feed intake during peak lactation
Neophobia
reluctance to accept a new food
aversive conditioning
train to avoid certain foods
how does metabolic rate affect FI
animals w/ increased metabolic rates consume more food per unit of BW
metabolic body size =
(BW) x .75
-can use to compare FI across species
how does smell play a role?
animals may reject a feed without even tasting it
how does fatigue play a role?
animals may become fatigued in seeking, ingesting, chewing, and ruminating feed
