1. Digestive Systems

2. Digestion and Absorption:
The process of digestion includes:
The prehension of food or feed
The mechanical chewing and grinding
Mixing with digestive acids and enzymes to chemically break down feedstuffs
The process of absorption includes:
Transport of the digested foods across the intestinal mucosa to the blood or lymph system

3. General Terms Prehension: to take into the mouth Mastication: chewing
Deglutition: swallowing
Regurgitation: the backward flow of food through the esophagus

4. Three Major Categories
Carnivore: consume flesh of other animals, examples are dogs and cats
Omnivore: consume both plants and flesh, examples are primates
Herbivore: consume plant material, examples are horses and cattle

5. Carnivore Very Well developed stomach Uncomplicated intestine
Limited fiber digestion

6. Omnivore Combination of carnivores/herbivores
More complicated GIT than carnivores
Colonic digesters
Pigs, humans
Cecal digesters
rat

7. Herbivore Cow, horse, rabbit Cow- ruminant
Each has a different type of GIT
Cow- ruminant
Horse- simple stomach, large cecum, large sacculated LI
Rabbit- larger stomach, very large sacculated cecum, unsacculated LI

8. Salivary Glands 3 pair Water - moistens food aids in swallowing
Parotid
Mandibular
Sublingual
Water - moistens food aids in swallowing
Mucin - lubrication for swallowing
Bicarbonate salts
Enzymes

9. Salivary Glands

10. Salivary glands

11. Different Digestive Tracts
Farm animals have a variety of digestive systems
Ruminants: have 4 different compartments to the stomach
Examples include cattle, sheep, goats
Nonruminants (also known as monogastrics)
Hogs, dogs, and cats have a single, simple stomach
Poultry have a two part stomach
Horses have a large, functional cecum

12. Pregastric vs Postgastric
Pregastric: Fermentation that occurs in the rumen of ruminant animals. It occurs before food passes into the portion of the digestive tract in which digestion actually occurs.
Postgastric: The fermentation of feed occurs in the cecum, behind the area where digestion has occurred.

13. Pregastric vs Postgastric
Ruminants
More efficient
Less intake
Non- ruminant herbivores
Only postgastric
Less efficient
Greater intake

14. Monogastric Systems
Mouth: prehension and chewing of food; some carbohydrate enzyme activity
Esophagus
Stomach
Storage
Muscular movements (break down food)
Secretes Digestive Juices (hydrochloric acid)
pH about 2

15. Monogastric Systems

16. Small Intestine Duodenum Active Digestion Site Produce enzymes
Pancreas
Helps to neutralize ingesta entering the SI
Liver
Produces bile; breaks down fats
Intestinal Walls

17. Small Intestine Jejunum Ileum Villi pH 6 to 7
Active in nutrient absorption
Ileum
Villi
pH 6 to 7

18. Large Intestine 3 Sections Active in water resorption
cecum
colon
rectum
Active in water resorption
Secretion of some minerals
*Bacterial Fermentation*

19. Horses are Different Saliva Esophagus contains no enzymes
may secrete up to 10 gallons/day
stimulated by scratching
Esophagus
only one way peristaltic movement
Impossible for regurgitation

20. Horses are Different Stomach Small Intestine
much smaller in comparison to other species
not very extensive muscular contraction
So how should we feed differently?
Small Intestine
same as pig but no gall bladder
Can’t handle a high fat diet

21. Horses are Different Large Intestine over 60% of GIT 4 parts cecum
large colon
small colon
rectum

22. Cecum and Large Colon Similar to Rumen bacterial cellulose breakdown
bacterial protein breakdown
VFA production
Water Soluble Vitamin production

23. Small Colon and Rectum Primary site for water resorption
Can become impacted with feed

24. Horse GI Tract

25. Avian Species Beak Esophagus no teeth
can be used to reduce particle size
Esophagus
ingesta holding and moistening
Salivary Amylase
Fermentation in some species

26. Avian Species Proventriculus Gastric juice production pH 4
Rapid pass through of food

27. Avian Species Gizzard (ventriculus) thick muscular wall
particle size reduction (similar to mastication)
nonglandular
normally contains grit
no enzymatic secretion

28. Avian Small Intestine
Functions in digestion and absorption of feed and nutrients just as in other monogastrics
pH is slightly acidic
Most enzymes found in mammals except?

29. Avian Large Intestine Contains 2 blind pouches instead of ?
Mostly water absorption
Some bacterial activity but less than in most mammals
very short in comparison

30. Avian Species

31. Ruminant Digestive System
Mouth
what is unique about the teeth?
Can only chew on one side of mouth at a time
Saliva production is continuous
Production about 12 gallons/d

32. Rumen Stomach
4 PARTS
reticulum
rumen
omasum
abomasum

33. Reticulum Honeycomb most cranial not truly separated from rumen
no enzymatic secretion
walls are tough, tend to catch heavy objects

34. Rumen Large compartment extends from diaphragm to pelvis papillae
Fermentation chamber
Majority of absorption of byproducts and conversion to volatile fatty acids

35. Rumen Digestion
Reticulorumen provides a favorable environment for bacterial fermentation
Continuous turnover of digesta and removal of fermented digesta
Anaerobic fermentation

36. Omasum Manyplies (Stockmans Bible) short blunt papillae very muscular
no enzymatic secretion
reduction of particle size
water resorption

37. Abomasum True Stomach First Glandular portion of the tract
Very similar in structure and function to nonruminant stomach

38. Other Unique Points Esophageal Groove
cardia to omasum
milk bypass
Rumination: The process where rumen contents are regurgitated, remasticated, and reswallowed for further digestion
Eructation: expulsion of accumulated fermentation gases from rumen via esophagus

39. Ruminant GI Tract

41. Rumination Regurgitation of ingesta with mastication
reticular contraction that concentrates ingesta at the cardia
increased inhalation of air at same time
contraction of diaphragm
ballooning of esophageal walls
ingesta sucked into esophagus
returned to mouth by reverse peristalsis

42. Rumination Excess liquids are swallowed Mastication commences
More time spent masticating here than initial intake
Amount of time ruminating is a function of diet composition

44. What do you know about Calves?
What do they eat?
What does this mean for their digestive system?
Any guesses??

45. The Calf Digestive System
For the first two weeks, a calf is a monogastric!
It uses only the abomasum to digest the milk!
The abomasum releases digestive enzymes to break down fats, carbs and proteins.

46. Calf Digestive System
When a calf drinks milk, it passes over the rumen to the abomasum via the esophageal groove.

47. Calves must develop the rumen!
During the weaning process, calves begin to take in less milk and more roughage.
This takes 3-4 months.
Milk fed veal…NEVER develop a rumen.

48. ESOPHAGEAL GROOVE
The suckling reflex and milk protein stimulate the groove to open.

49. Rumen Contents and Motility
Rumen contents are not uniform
Occur in stratified layers
Change from ventral to dorsal
Rumen mat
high concentrate diets eliminate mat
more viscous fluid in high grain diets
lowest dry matter in high forage diets

50. Rumen Contents and Motility
Motility of rumen mixes contents
Divided into
primary contractions
secondary contractions
Contractions require up to 50 seconds to complete

51. Rumen Contents and Motility
Contractions begin with reticulum
Progress dorsally
Finish with ventral blind sac and ventral pillars

52. Rumen and Acute Acidosis
Optimal rumen pH is 6.7
Variation in pH is normally +/- 0.5
Introduction of high grains result in
breakdown of rumen mat
proliferation of facultative anaerobes
these produce high levels of lactic acid

53. Rumen and Acute Acidosis
Lactate is a much stronger acid that other VFAs
In severe cases lactate can make-up well over 50% of total rumen acids
Succinate and Formate can also appear in high quantities

54. Rumen and Acute Acidosis
Increased acids can reduce pH as far as 4.0
Severe rumenitis occurs at these pH levels
Absorption of lactic acid results in systemic acidosis
All chronic acidosis results in rumen parakeratosis

55. Corn Fed Cattle in early stages

56. Corn Fed Cattle in early stages
Clinical Signs
Within 24 hours of grain ingestion animals may be recumbent, staggering, or standing quietly. Death may occur within 24 to 72 hours. The rumen is usually static, diarrhea, and a normal temperature are commonly seen.

57. Should we be feeding cattle corn?
What do you think??

58. Factors Affecting Digestibility
Rate of passage: increased rate of passage of digesta through the tract reduces digestibility
Factors increasing rate of passage include:
Increased level of feeding/intake (ruminants)
Finer processing (such as grinding) of feed
Note: grinding grain usually increases digestibility but grinding hay decreases digestibility

59. Bloat
Ruminants continually belch, once each minute, to get rid of the gas. Occasionally belching stops and gas builds up in the rumen to cause bloat.

60. Bloat
As the gas builds up the left flank balloons out. The pain from this causes the animal to try to kick its belly or it stands with its back legs wide apart. It has difficulty in breathing.

61. Bloat

62. Bloat
The animal may be in distress for several hours but in bad cases of bloat the animal will be found lying on its side and death can occur in a few hours.

63. Causes of Bloat
Bloat can occur when the animal grazes on lush young pasture, particularly if the pasture is wet. Some plants, e.g. clover, lucerne and alfalfa are especially dangerous in causing bloat but any fast growing plants can cause it.

64. Causes of Bloat
Sometimes ruminants kept by the household and fed only feed such as dry bread can develop bloat.

65. Prevention of Bloat
Avoid moving animals to wet pasture, especially first thing in the morning. · Do not allow very hungry animals to graze a pasture. Offer dry, cut grass first before turning out to graze.
· Keep a watch on animals at pasture.

66. Treatment of Bloat
Making the animal belch is one way of treating bloat. You can do this by:
· Massaging the distended rumen through the abdominal wall. · Tying a stick in the mouth, crosswise like a horse's bit. · Tickling the throat. · Make the animal walk around for about half an hour.

67. Treatment of Bloat
If these methods fail then give a drench (drink) to the animal
The drench used can be one of the following:
Two large spoons of washing up liquid, e.g. Fairy, Lux.
A small bottle of peanut, soya or linseed oil
Use a commercially, available medicine

68. Treatment of Bloat
In severe cases the animal may not belch and it will die. In such cases puncturing the left flank with a sharp knife or trocar and cannula to release the gas is necessary, it will be necessary for you to act quickly as any hesitation could lead to the death of the animal.

69. Treatment of Bloat

70. KNOW HOW TO SEE THE SIGNS!!

71. KNOW HOW TO SEE THE SIGNS!!

72. KNOW HOW TO SEE THE SIGNS!!

73. KNOW HOW TO SEE THE SIGNS!!