Non-Ruminant Herbivore Digestive Physiology

what are pregastric fermenters

fermenting prior to gastric stomach and SI

what are hindgut fermenters

fermenting after SI

what are examples of cecal fermenters

rabbit, Guinea pig, chinchilla, rat

what are examples of colon fermenters

horse, gorilla, elephant, rhino, koala

t/f is animal ferments before or after the gastric stomach and SI has a huge effect on efficiency of utilization of fermentation products

true

microbial fermentation is only useful if digestive system can

retain digesta and microbes for long periods maintain suitable environment for fermentation

volume available for fermentation is greatest in

ruminants (over 75% of GIT devoted to fermentation)

longer retention time will lead to

more fermentation and more contact time with microbes

what are the pregastric fermenters GIT modifications

have compartment in stomach to selectively sort and retain fibrous material

what are the hindgut fermenters GIT modifications

larger cecum and/or larger colon

the compartmentalized stomach has

one or more pouches for fermentation separate from the gastric region

how many pouches are there for fermentation

2-4

what is different about the cardiac region in foregut fermenters

expanded cardiac region for fermentation

foregut fermenters can be

bulk roughage feeders or browsers

what is the only bulk roughage feeder example KM gave us

hippo

are any of the non-ruminant herbivore domesticated species foregut fermenters

naur

sloth has a

3 chambered stomach

kangroo has a

long, tubular stomach not really chambers

because cecum is a blind sac, digesta must pass out via

route of entry, allows cecum to selectively retain fractions of feed

how many times a day do the cecal contents enter the colon (cecal fermenters)

1-2 times/day

cecal fermenters have a

evolved strategy to separate and excrete indigestible fiber

in cecal fermenters, separation of particles is based on

density in colon

less dense material will

remain in lumen, move through colon ex: larger fiber particles

denser, smaller particles will

remain around perimeter and move into cecum for fermentation ex: proteins, easily digestible fiber

hard feces are

indigestible fiber

soft/night feces are

cecotropes, cecal contents coated with mucus

why dos animal eat cecotropes

contains B vitamins and microbial proteins

what are the 3 main VFA products of fermentation

acetate, propionate, butyrate

what are the major functions of a hindgut fermenter

mixing of contents ileum and colic epithelium secrete bicarb reabsorb fluids and electrolytes

mixing of contents will

promote fermentation and expose contents to mucosal surface for absorption of VFA (control pH)

why is secretion of bicarb important

buffering VFA to maintain pH

why is hindgut fermentation less efficient than foregut fermenters

less opportunity to absorb VFAs, can't utilize microbial protein

colon fermenters have

enlarged colon and cecum for microbial fermentation -ferments material that resists breakdown AND starch/sugar

how much non-structural carbs reach hindgut affects

risk of colic/ laminitis

protein is a source of

Nitrogen for microbes and microbes utilize urea recycling to hindgut

the more structural carbs

more difficult to digest

acid exposure from gastric stomach to structural carbs will

increase susceptibility to microbes

what substrates are in hindgut fermenters

structural, non-structural, proteins

what are the 2 important areas of size reduction in equine hindgut

pelvic flexure junction of large to small colon

what is haustra

saclike invaginations in cecum and colon

how long does it take for soluble digesta to reach cecum

~2 hours after ingestion, longer depending on particle size

cecal motility will

mix slowly and transport from haustra to haustra

every 3-4 minutes, mass movement contraction to

move digesta from cecum to right ventral colon via cecocolic orifice

haustral segmentation contractions will

mix to promote fermentation and aid in VFA absorption

propulsive peristalsis originates near cecum following mass movements to

propel digesta toward left ventral colon

antiperistalsis movements in left ventral colon will

resist digesta flowing forward leads to retention and mixing

pelvic flexure has a narrow diameter and antiperistalsis movements to help

retain larger particles for further fermentation allows liquid and soluble material to pass through

actions in dorsal colon mimic

ventral colon

diameter of dorsal colon decreases at

junction of large and small colon-creates impedance to digesta flow

retropulsion originates near

junction, causing mixing and allows more fermentation

segmentation contractions of small colon form

fecal balls

small colon will recover

water, electrolytes, and VFAs