Ruminant Anatomy and Physiology

Question 1

What are the 4 regions of the ruminant stomach?

Answer 1

• Reticulum –> rumen –> omasum –> abomasum

Question 2

Describe the stomachs in a newborn calf

Answer 2

• Abomasum is largest –> needed for digestion rather than fermentation

Question 3

Describe the stomach in a 5 YO cow

Answer 3

• Rumen is now large and takes up whole left side of abdomen

- Liver is pushed up cranially

Question 4

Describe the stomach of a 6 YO pregnant cow

Answer 4

• Uterus displaces rumen dorsally and abomasum cranially

Question 5

What feed causes the rumen to become functional?

Answer 5

• Grain

Question 6

What structure allows milk to bypass the rumen and enter the abomasum in the calf? What happens when milk enters the rumen?

Answer 6

• Oesophageal groove

- Rumen putrefaction

Question 7

What organisms are found in the rumen and what are their functions?

Answer 7

• Bacteria –> digest cellulose (only seen with EM)
• Protozoa –> control bacteria numbers
• Fungi – aid bacteria in cellulose digestion

Question 8

What is the “true” stomach of the cow

Answer 8

Abomasum

Question 9

What is the purpose of external ruminal palpation?

Answer 9

• Helps determines the consistency of the rumen contents

Question 10

Why do you want to auscultate the rumen?

Answer 10

• Determine rate/ strength of rumen contractions, rumen volume, and rumen contents

Question 11

What is atony?

Answer 11

• Complete absence of reticuloruminal motility

Question 12

How does atony occur?

Answer 12

• Absence of excitatory inputs or increase in inhibitory inputs to the gastric center of the hypothalamus
• Depression of gastric center
• Vagal failure or motor pathway failure

Question 13

What is hypomotility?

Answer 13

reduction in frequency or strength of primary contraction

Question 14

How does hypomotility occur?

Answer 14

• Decreased excitatory drive to gastric center
• Increased inhibitory inputs
• Weakness of the motor pathway

Question 15

What is the importance of primary contraction frequency?

Answer 15

• Indicates the overall health of the rumen

Question 16

What can prevent secondary/ eructation cycle?

Answer 16

• The cardia being blocked by foam or fluid

Question 17

What occurs during rumination

Answer 17

• Food is broken down further

- Saliva is ingested, adding bicarb to decreases acidity of rumen contents

Question 18

What are you looking for when examining feces?

Answer 18

• Amount, color, odor, consistency, degree of digestion

Question 19

How can you collect rumen fluid?

Answer 19

• Ororuminal collection and rumenocentesis (better)

Question 20

What must you be aware of with rumen samples

Answer 20

• Quickly test sample as protozoa activity changes over time

Question 21

What are normal colors of rumen fluid?

Answer 21

• Olive to brownish grey for hay

- Yellowish brown for grain/ silage ration

Question 22

What are abnormal rumen colors?

Answer 22

• Black/ green for rumen stasis

- Milky gray/ brown is lactic acidosis

Question 23

What is considered normal rumen consistency? Abnormal?

Answer 23

• Normal –> slightly viscous

- Abnormal –> waterly (anorexia), frothy (bloat or vagal indigestionn)

Question 24

What are normal and abnormal rumen odors?

Answer 24

• Normal –> aromatic

- Abnormal –> acidic (lactic acidosis), rotting odor (rumen putrefaction)

Question 25

When is the best time to measure rumen pH? What is the normal rumen pH? Abnormal?

Answer 25

• Best to measure 2-4 hrs after concentrate or 4-8 hrs after TMR
• Grass feed is pH 6-7
• TMR 5.5-6
• > 5.5 is lactic acidosis

Question 26

What is the purpose of methylene blue reduction?

Answer 26

• Indicates anaerobic ruminal bacteria
• Normal is 2-6 min
• > 10 min is transfaunation

Question 27

What is the purpose of nitrate reduction test?

Answer 27

• Measures abomasal disease, abomasal reflux, obstruction of intestinal flow

Question 28

How can you clinically assess the abomasum?

Answer 28

• Percussion and auscultation, abdominocentesis, blood work