the preparation of food for absorption
What are the 3 major methods (mechanisms) of digestion?
physical/mechanical, chemical & enzymatic
Why do different animals use very different kinds of feeds?
the digestive system of the animal determines what it can eat. the more complicated the feed, the more complicated the digestive system
what are the two stomach types in livestock?
monogastrics & ruminants (more than one stomach compartment)
what is the subcategory of stomach type?
cecal fermenters = hind gut fermenters
what is prehension?
seizing & conveying of food to the mouth
what is mastication?
explain the function of chewing of herbivores
they chew thoroughly to allow bacterial enzymes to have access to cellulose by increasing feed surface area
what is salivation?
secretion & mixing of saliva with food
what dictates the amount of saliva that is produced by the various species?
species & diet
how much saliva is produced by carnivores, omnivores and herbivores?
carnivores = smallest, 200 ml/day omnivore = intermediate, 1500 ml/day herbivores = most, horse - 40 L/day, cow - 120+L/day
what are the components of saliva?
water, electrolytes, proteins (lysozymes, salivary amylast & lipase)
8 functions of saliva
lubrication, solvent, washing, disinfectant, buffer, nutrients, antifrothing, excretory
what is deglutition?
what is the role of the stomach in digestion?
stores food & performs mechanical & chemical digestion
what are the 3 portions of the small intestine & what are the functions of each?
Duodenum - main site of food breakdown in the sm. intestine
Jejunum - absorption of the end products of digestion
ileum - forms the connection to the large intestine, some absorption here
what does bile do?
assists in digestion & absorption of fats by a detergent action that helps emulsify fats by forming a complex with fatty acids
what does pancreatic juice do?
contains important digestive enzymes
what are the functions of the pancreatic digestive enzymes?
trypsin, chymotrypsin, carboxypeptidase & aminopeptidase = digest proteins
intestinal lipase = breaks fats into fatty acids & glycerol
amylase = digest starch
function of large intestine.
water, electrolytes, vitamins, minerals & volatile fatty acids are absorbed here
what do bacteria do in the gut of a monogastric herbivore?
They help do what the rumen does but not as well. Functions in the digestion of cellulose & in the microbial production of b-complex vitamins
why do rabbits practice coprophagy (cecotropy)?
they adapted to make use of the unused microbial proteins by eating the contents of the cecum directly from the anus and digesting it
how does an animal defecate?
the defecation reflex is stimulated by the pressure of feces in the rectum —> the reflex is assisted by the parasympathetic nervous signal that intensify the peristaltic waves of the large intestine —> many animals use the valsalva maneuver (breathing deeply, closing the glottis & flexing the abdominal muscles) to put pressure on the fecal contents to expel them
what are the components of urine?
Nitrogen compounds (urea & uric acid), sulfurous metabolites, minerals (Cl, K, P, Na) & water
what is the major anatomical difference in ruminants & nonruminants?
the complex stomach of the ruminants
describe the anatomy of the ruminant tract
4 compartments: rumen, reticulum, omasum, abomasum
what are the common names of the 4 ruminant stomachs?
rumen = paunch reticulum = honeycomb, hardware stomach omasum = manypiles, Stockman's Bible abomasum = true stomach
what is the relative volume of each compartment in the ruminant “stomach”?
rumen - 80%
reticulum - 5%
omasum - 7 to 8%
abomasum - 8 to 9%
what is the esophageal groove & what does it do?
it is a muscular groove that can contract & form a tube that acts as a bypass of the rumen & empties into the abomasum
what is the function of the rumen?
the rumen acts as a site of anaerobic bacterial fermentation
what are the VFAs of importance in the rumen & what does the animal do with them?
acetic acid, propionic acid, butyric acid & valeric acid. The VFAs are absorbed through the rumen wall & supply 50% of the energy requirement for the ruminant.
what is the relative quality of the protein manufactured in the rumen?
protein quality is equivalent to soybean meal which is an excellent quality feedstuff
name the 5 nutrients produced as a result of rumen fermentation.
protein, energy, vitamin k, b-vitamins & essential fatty acids
what is the function of the reticulum? omasum? abomasum?
reticulum = site of microbial action, pacemaker for rumen contractions omasum = unclear function...maybe water & VFA absorption abomasum = true glandular stomach/same function as monogastric stomachs
what is eructation? what are the consequences if a ruminant is unable to eructate?
eructation is belching gas. Contractions in the upper sacs of the rumen force the gas forward & down. The esophagus dilates & allows gas to escape.
if a ruminant is unable to eructate, it will bloat
how can you treat /prevent bloat?
prevention = do not allow ingestion of legumes & increase forage portion of the diet treatment = feed poloxalene (bloatguard) or feed 2-3 oz. laundry detergent/day emergency = use a trocar & cannula (punctures rumen & releases gas)
describe the extent of postgastric fermentation in the ruminant.
5-15% of total digestion occurs in the large intestine & cecum. VFAs will be produced & absorbed from the fermentation.
how long does it take feed to get through the ruminant tract?
about 12 hours for the first material through the tract
3-4 days is the average time spent in the tract
10 days for the last material through the tract
what is symbiosis?
the beneficial agreement between microorganisms & the animal where both parties benefit from one another
how do ruminants & its microbes qualify for status as symbiotic partners?
ruminants and microbes live in a form of symbiosis called mutualism. microbes benefit by the environment that is provided by the animal to support them & the animal benefits b/c the microbes digest feed it could not otherwise use & generates nutrients it needs
what kinds of microbes are found in the rumen?
bacteria - vast # of different types are found in the rumen
protozoa - 12 or so different species in the rumen
yeast & phages - 9 or so
what is the relative importance of the VFAs to the energy contribution of a ruminant animal?
VFAs are a major end product of ruminal fermentation. It contributes 50-70% of energy to the animal
what is the composition of the gas coming off a ruminant fermentation?
CO2 - 65%
N - 25%
CH4 - loss of energy
O2, H2, H2S - some
how does diet affect VFA concentrations in the rumen?
grain diets = 100-120 mmol VFAs, pH of 5.5-6.0
forage diets = 60-80 mmol VFAs, pH of 6.5-7.0
what are ionophores? what do they do & what is the outcome of feeding them?
ionophoes are feed additives that alter ruminal metabolism. they favor propionic acid-producing species. the outcome is increased propionate & decreased acetate as well as decreased methane & lactate
why feed Megalac?
it can be used to increase the fat in a ration. it increases the milkfat & helps with energy balance
what is bypass protein & what are the implications to production of feeding it?
it is an undegradable protein
why is forage utilization enhanced by feeding adequate nitrogen to the ruminant?
the positive associative effect which is when one feed increases the utilization of a second feed.
reproduce the horse digestive tract in rough drawing & label all parts
esophagus - stomach - duodenum - jejunum - ileum - large cecum - large colon - small colon - rectum - anus
describe the significance of the horse being a cecal fermenter.
they can use roughage b/c they have an active cecal bacterial population that digests fiber. the cecum contains bacteria population producing VFAs. Absorption of water & VFAs occurs here.
what is the purpose of saliva in the horse?
lubrication of food
how much saliva does the horse produce?
40 L/day = 10 gallons/day
why doesn’t the horse regurgitate?
the horse is incapable of regurgitation due to it’s very strong cardiac sphincter in its stomach. Also, the horse has one-way peristaltic movements in the esophagus
what is the relative capacity of the horse’s stomach?
why is the horse prone to stomach disorders?
the stomach is very small & it does not have extensive muscular activity & the feed tends to arrange itself in layers b/c of this.
what is the function of the horse’s small intestine?
absorb nutrients & secrete bile into the duodenum
describe in detail what happens in the large intestine & cecum of the horse
large intestine is divided into the cecum, large colon, small colon & rectum.
bacterial synthesis of water-soluble vitamins occurs & they are absorbed from the large intestine in limited amounts.
why must we feed horses their amino acids & we don’t have to feed the cow any?
horses cannot digest the microbial protein manufactured in the cecum, therefore, horses must be fed essential amino acids. the cow has a symbiotic relationship with the microbial bacteria where the bacteria digests the protein for the cow to absorb.
what are the major anatomical differences & functions in the avian & the pig?
avian - presence of the gizzard, cloaca & crop
the crop is a dilation of the esophagus that is present in most but not all avian species. it functions as a storage organ & moistening reservoir.
the gizzard or ventriculus is a high specialized grinding organ that contains grit to aid in the grinding of feed.
the cloaca is the common orifice for waste elimination, copulation & egg laying in females.
how does digestion occur in the avian?
food moves from the mouth into the esophagus and then into the crop.
food then moves from the crop into the proventriculus (true stomach)
from there it moves to the gizzard (ventriculus) where the food is ground into small bits with the help of grit & then enters the small intestine where digestion occurs as well as absorption of feed & nutrients.
what is an anatomical difference b/n the chicken & the pig?
chicken lack teeth, have a crop, have a gizzard and a cloaca.
the pig lacks this gastric enzyme
volume of the pig’s stomach
pH of pig saliva
the pig has 3 pairs of glands that produces saliva…name them
parotid, mandibular, sublingual
the time it takes for a pig to empty a full stomach
length and volume of pig’s sm. intestine
60 ft & 2.5 gallons
name the 8 pancreatic enzymes produced in the pig
trypsin chymotrypsin carboxypeptidase pancreatic lipase pancreatic amylase maltase sucrase lecithinase
bile is secreted from which organ in the pig? where is it stored?
bile is secreted by the liver & stored in the gall bladder
function of bile in the pig
aids in the digestion & absorption of fats and soluble vitamins, activates pancreatic lipase & accelerates action of pancreatic amylase
length & volume of large intestine of the pig
16 ft & 2.5 gallons
function of the large intestine in the pig
absorb water & act as a reservoir for the waste materials that constitute as feces
the pig is considered what type of eater?
the pig’s pancreas produces what compound to aid in CHO metabolism?
the pig is the only farm mammal in which any amount of this enzyme is secreted in the saliva:
what is the function of salivary amylase in the pig?
begins to break down starch in the feed - there is very little nutritional importance as the feed does not stay in the mouth long enough for starch breakdown.
the pig has a simple stomach and is considered what?
a monogastric = nonruminant