Hindgut fermenters

Question 1

What are 4 advantages of being a hindgut fermeter?

Answer 1

• nutrients not exposed to microbial fermentation, more available for host
• gastric and intetinal digestion may expose more fermentable substrate
• digesta arrives at hindgut predigested
• rabbits have a symbiotic relationship with microbes

Question 2

What are 2 disadvantages to hindgut fermentation?

Answer 2

• protein absorption in intestine may lead to deficiency in hindgut, may restrict microbial growth
• hindgut not developed for protein digestion/absorption so microbial protein is wasted

Question 3

What do caeco-colic motility patterns control?

Answer 3

• substrate supply
• microbial population pH
• particle size and separation

Question 4

Describe the process of colonic fermentation in horses

Answer 4

1. intestinal chyme arrives at caecum after 24 hrs mixing in stomach
2. chyme mixed in caecum
3. caecum controls emptying of chyme into RVC
4. in colon peristalsis and retroperistalsis mix and break up digesta, segmentation ensures it stays in good contact with the absorptive epithelium
5. digesta retained in LVC due to selectivity of pelvic flexure - pelvic flexure is pacemaker of ventral colonic contractions
6. complete fermentative breakdown of particulate matter takes 1-3 days

Question 5

What characterises the activity of the small colon?

Answer 5

• segmentation
• completion of water reabsorption
• formation of faecal balls

Question 6

How much pancreatic juice is secreted into the SI and what is its function?

Answer 6

• 19L/day
• alkaline buffer
• pH control
• contains predigested ingesta

Question 7

How much fluid does the hindgut secrete?

Answer 7

12L/day

Question 8

How much fluid is reabsorbed by the hindgut?

Answer 8

30L/day

Question 9

Describe the metabolic activity of the hindgut

Answer 9

• Na/H pump facilitates VFA absorption
• Cl exchanged for HCO3-, helps to buffer lumen and stop pH dropping too low

Question 10

Describe the ferementation process

Answer 10

1. 20L fluid/day passes from upper SI to hindgut
2. liquid stored in caecum and mixed slowly then released into RVC
3. Pelvic flexure triggers powerful contractions in ventral colon- additional 12L fluid secreted here
4. final mixing and fermetation occurs in the dorsal colon
5. VFA and water absorption occurs before gradual dehydration in small colon

*microbes/MP lost in faeces and not utilised by horse

Question 11

Define ‘caecotroph’ and ‘caecotrophy’

Answer 11

• caecotroph - fermented material transported from caecum to anus
• caecotrophy - consumption of faeces

Question 12

Describe fermentation in the rabbit

Answer 12

1. Ingesta arrives at caecum
2. caecal motility patterns break down plant matter by rostral contractions
3. suitably small fermented material passes from caecum to colon for dehydration and faecal ball formation
4. early morning - diff. recto/colonic contractions voids hard faeces then soft material directly from caecum which are eaten and digested again
5. caecal fermentation products returned to stomach where MO protein and vitamins are digesteed conventionally