Pathology of the ruminant forestomach

Question 1

What determines rumenal papillae height development?

Answer 1

Roughage, especially concentrates is major stimulus for papillae growth
Growth also stimulated by propionate and butyrate from fibre fermentation

Question 2

What might lead to clumpy, hypertrophic, hyperkeratotic papillae? What might this predispose to?

Answer 2

A diet that is too high in concentrates without enough fibre
Get clumpiness, hyperkeratosis, hyperplasia and hyperpigmentation
May predispose to adhesion of plant fibres or hair to the rumen mucosa > inflammation = “barley beef rumenitis”

Question 3

What effect will a poor plane of nutrition have on papillae development?

Answer 3

Small, blunt, stumpy papillae

Question 4

Is there anything other than unbalanced dietary fibre that can cause hyperkeratosis of the ruminant forestomach?

Answer 4

Hypovitaminosis A

Question 5

What is the normal pH for rumenal fluid? What common feed supplement might cause a slightly more alkaline pH?

Answer 5

5.5 - 7.5
Feeding urea (to feed bacteria) can lead to more alkaline rumen

Question 6

What two disease processes would you suspect if the rumen mucosa were difficult to pry off post mortem?

Answer 6

Rumenitis

Rumenal fibrosis

Question 7

What is rumenal tympany?

Answer 7

Bloat = dilation of the rumen with gas

Question 8

What are the two major mechanisms for eruction being prevented?

Answer 8

1. Physiological obstruction due to vagal nerve damage

2. Physical obstruction e.g stiff, foamy contents or a mass

Question 9

What is the leading cause of primary bloat in ruminants?

Answer 9

Consumption of fresh legumes e.g clover and alfalfa

Question 10

Outline the mechanism for primary bloat.

Answer 10

Lush legume consumption > less salivation stimulated > increased viscosity of rumen content > soluble proteins released from legume by bacteria rise to surface of fluid, become denatured and insoluble > legume acids drop pH, also less HCO3- being delivered via saliva > favorable conditions for thick stable foam formation in rumen, which can prevent eructation

Question 11

Outline the mechanism for ‘feedlot bloat’

Answer 11

High concentrate, low roughage ration > decreased saliva production and gradual change in rumen bacteria > increased production of polysaccharides > increased viscosity of fluid > stable foam formation

Question 12

Other than massive abdominal distension, what is seen in bloated cattle?

Answer 12

Dyspnoea due to pressure on diaphragm and lungs

Hindlimb congestion due to compression of caudal vena cava and circulatory failure

Question 13

What genetic factor might predispose cattle to bloat?

Answer 13

Genetic tendency to produce less saliva

Question 14

An oesophageal bloat line may be seen at post mortem in animals that have died from bloat. Which side is redder and which is paler?

Answer 14

Redder = cranial

Question 15

What is a trichobezoar composed of?

Answer 15

Hair, wool

Question 16

What is the potential significance of a trichobezoar?

Answer 16

Boredom, pica, skin disease or insufficient dietary fibre

Question 17

What is a phytobezoar composed of?

Answer 17

Plant fibres

Question 18

What is the potential significance of a phytobezoar?

Answer 18

Rough feed, oral disease, dental disease

Question 19

What does ‘vagal indigestion’ refer to?

Answer 19

A clinical syndrome resulting from a physical or functional outflow obstruction of the forestomach or abomasum leading to distension of the rumen and reticulum

Question 20

List three possible causes of vagal indigestion

Answer 20

1. Damage to vagus nerve due to fibrous entrapment following an episode of TRP
2. Pregnancy leading to absomasal displacement and impaction > distension > atony
3. Obstruction to rumenal emptying e.g foreign body, neoplasia, abscess > distension > atony
4. Trauma following displacement of abomasum

Question 21

Give two possible PM findings for vagal indigestion

Answer 21

1. Distended rumen with watery contents

2. Impacted abomasum and/or omasum with dry feed

Question 22

What is the most common cause of rumenitis?

Answer 22

Rumen acidosis

Question 23

What is diagnostic of ruminal acidosis at PM?

Answer 23

• pH of less than 5 (beware post mortem rises though)
• swollen papillae with hydropic degeneration of epithelial cells +/- coagulative necrosis, formation of mucosal erosions and ulcers
• neutrophils infiltrating mucosa

+/- lots of grain +/- voluminous contents
+/- evidence of dehydration e.g sunken eyes

Question 24

What are three other things that can cause rumen ulceration and predispose to fungal rumenitis?

Answer 24

Antibiotic therapy especially calves
Reflux of abomasal contents
BVDV infection

Question 25

What are the two most common rumenal parasites? Clinical significance?

Answer 25

Gongylonema spp. = incidental finding

Paramphistomum (conical fluke) = large numbers may cause atrophy and hyperkeratosis of rumenal papillae

Question 26

What sort of rumenal tumour might BPV-2 cause?

Answer 26

Fibropapilloma - proliferation of fibroblasts