3b Digestive Physiology of Horses Flashcards
What is the role of the GI tract?
- digestion and absorption
- microbiome
- immunity
- secretions and excretion
Horses have a similar GI anatomy compared to which animal?
pig
How much the the horse GI tract weigh?
- 500kg
How long is the SI?
20-24m
How long is the LI?
9-10m
How does horse absorb microbial protein?
- some essential amino acid absorption occurs in handgun
What macronutrient is the horse best adapted for to utilize?
- fibre
What is the purpose of saliva?
- secretion stimulated by mastication
- contains small amount of bicarbonate
- provides buffer against stomach acid
How many teeth do horses have?
- 36
- 12 incisors, 12 premolars, 12 molars
What 3 regions is the stomach divided into? what do they do?
- oesophageal region (squamous epithelium)
- fundic region (glandular epithelium, parietal cells HCl, zymogen cells pepsin)
- pyloric region (glandular epithelium, gastrin)
Where can microbial fermentation occur in the stomach?
- oesophageal and fundic region
What is the emptying time of the horse compared to dogs and cats?
- horse 120 min
- dog 5-10 hours
- cat 3-6 hours
What is the function of the exocrine pancreas?
- secretes enzymes and bicarbonate salts into the gut
- enzymes: inactive proteases, lipases and amylases
What is the function of the endocrine pancreas?
- secrete hormones into blood
- hormones: insulin, glucagon
What is the function of the liver?
- produce bile which drains into SI to emulsify fat
- NO GALL BLADDER
Why the adaptive feature of missing a gall bladder?
- diet lower in fat so less need to large secretion of bile
- eat more frequently so don’t need a collection organ
Describe the caecum.
- very large (1m, 25-35L capacity)
- microbial population
- responsible for microbial synthesis of SCFA and protein
Describe the large intestine of the horse.
- 4 large compartments and 3 major flexures
- right ventral colon (sternal flexure), left ventral colon (pelvic flexure), left dorsal colon (diaphragmatic flexure), right dorsal colon
- small colon ends in rectum
How do small and large intestinal histology differ?
- large intestine contains no villi and deeper crypts
What are the ways the intestine increases capacity?
- coiling
- folds
- villi
- microvilli
What are the enzymes involved in protein digestion and where do they originate
- stomach: pepsin
- pancreas: trypsin, chymotrypsin, elastase, carboxypeptidase
- intestine: aminopeptidases, dipeptidases, tripeptidases
Why are di and tri peptides absorbed into enterocytes as well as single amino acids?
- more efficient as di and trip peptides take same amount of energy to absorb as single AA
How are AA transported?
- different transport systems based on AA classification
- most AA transport is active transport
What are the enzymes involved in carbohydrate digestion, where do they originate, what is their action?
- pancreas: a-amylase (starch)
- intestine: glucoamylase (alpha-limit dextrins), maltase (maltose), isomaltase (maltotriose), sucrase (sucrose)
How are carbs absorbed?
- sodium dependent transporter
- some diffusion, mostly active transport
What enzyme digests fat?
- lipase from pancreas
- breaks down triglycerides into free fatty acids and monoglycerides
How are fats absorbed?
- lymph
In what order are SCFAs absorbed in the large intestine?
acetate > propionate > butyrate
How much energy do horses acquire from SCFA?
50-70%
Why is a horse micro biome very sensitive to dietary change?
- micro biome needs to titrate
- dogs and cats rely less on micro biome and can adapt to large diet changes quicker
What are the 3 ways in which SCFA are absorbed?
- passive
- facilitated
- symporter
How do SCFA interact with the pancreas?
- provide signals to islets which regulate insulin release
