Rumen disorders Flashcards
Describe the pathophysiology of rumen acidosis
Consumption of easily digestible carbs -> bacterial population shifts to gram-positive in 2-6 hours -> fermentation is altered and there are increased volatile fatty acids, lactate, and glucose -> rumen pH is reduced -> protozoa decline and lactate accumulates more -> if pH drops below 5.0, gram-negative bacteria reduce greatly and endotoxin is released, if pH drops below 4.5, Lactobacillus dominates and produces lactate and histamine -> systemic lactic acidosis -> rumen epithelial damage, possible sepsis
How does rate of dietary adaptation affect rumen acidosis
Sudden introduction of fermentable carbs leads to increased risk of acidosis; dietary adaptation is necessary to build up populations of lactate-using bacteria
What types of feed predispose an animal to rumen acidosis
High sugar feeds, wheat and barley > corn > sorghum > oats
How does processing method affect likelihood of developing rumen acidosis
Small particle size, heat or pressure cooking, and high moisture of grain increase starch availability increasing risk of acidosis
How does forage availability affect likelihood of developing rumen acidosis
Feeding forage with grain increases chewing and salivation which increases the buffering of rumen pH and decreases chances of rumen acidosis. TMR have lower risk of acidosis and feeds that allow grain to be sorted preferentially over forage have higher risk of acidosis.
How does frequency of grain consumption affect rumen acidosis risk
Feeding small grain meals frequently decreases the risk of acidosis, feeding grain ad lib increases the risk
What life stages are predisposed to developing rumen acidosis
Feedlot animals, dairy cattle transitioning from dry to lactating or in early lactation, and show animals are predisposed to acidosis
What are clinical signs of acute rumen acidosis
Anorexia, depression, rumen distension, atony, and sloshy contents, dehydration, tachycardia, cold extremities, weakness or recumbency, watery diarrhea
How does the pathophysiology of rumen acidosis cause clinical signs
Rumen osmotic pressure is increased which causes fluid accumulation in the rumen leading to systemic dehydration and decreased peripheral perfusion. Increased rumen osmolality impairs VFA absorption and bicarb entry which worsens acidosis. Hyperosmotic diarrhea develops, worsening dehydration and hypovolemia. Low pH, high concentrations of undissociated butyric acid, and rumen distension can lead to rumen atony and bloat.
What are the clinical signs of chronic rumen acidosis
Clinical signs include decreased feed intake, decreased performance, increased culling rates, increased laminitis. Low milk fat concentration can also be seen.
What diagnostic findings are associated with acute rumen acidosis
History, rumen fluid that is watery, sour-smelling, contains a lot of grain, has a pH <5.5, lacks protozoa, and is dominated by gram-positive bacteria. Lab tests showing metabolic acidosis, increased anion gap, hemoconcentration and pre-renal azotemia.
How do you diagnose subacute rumen acidosis
Presumptive diagnosis can be made based on evaluation of ration and feeding practices and observing response to feeding changes. Rumenocentesis of several cattle performed post-feeding showing a pH <5.5 in more than 2 cows indicates subacute acidosis.
How do you decide which animals to treat for rumen acidosis in a herd outbreak
Treat animals that are likely to respond, euthanize animals that are already recumbent
How is rumen acidosis treated
Remove further grain. Evacuate rumen contents with rumenotomy or rumen lavage (rumenotomy generally has better results when possible). Correct dehydration and systemic acidosis by administering IV isotonic sodium bicarbonate and 500mL calcium gluconate IV (don’t mix with sodium bicarb solution). Neutralize rumen pH with oral administration of magnesium hydroxide or sodium bicarb. Reinoculate the rumen with rumen fluid from a healthy cow. Administer systemic antibiotics (procaine penicillin, 7-10 days) to target facultative anaerobic bacteria. People sometimes also treat with antihistamines, NSAIDs, and thiabendazole.
How is subacute/chronic rumen acidosis treated
Managed with dietary changes of the herd
What are possible sequela to acute rumen acidosis
Peritonitis, liver abscesses, caudal vena cava syndrome, rumen epithelial hyperkeratosis/parakeratosis, laminitis (chronic > acute)
How can rumen acidosis be prevented
Manage feed type and schedule, incorporate ionophores into feedlot and dairy cattle feed (inhibit gram-pos bacteria but not specifically approved for prevention of acidosis), add buffers to the ration (sodium bicarb, sodium sesquicarbonate, magnesium oxide), increased protein or NPN diet (increases ammonia and buffering), lactobacillus or yeast cultures in diet
What circumstances frequently lead to simple indigestion
Moldy or spoiled feed, heat or cold damaged feed, indigestible roughage, too much feed, new type of feed
What are clinical signs of simple indigestion
Decreased appetite, decreased milk production, rumen hypomobility, mild bloat, abnormal feces
How is simple indigestion diagnosed and treated
Rule out other causes, rumen fluid analysis may reveal changes. Signs recover spontaneously once feeding error is corrected.
What are clinical signs of vagal indigestion
Rumen hypo- or hyper-motility, decreased appetite, abdominal distension, weight loss, reduced milk production and fecal volume, abnormal rumen shape, sometimes bradycardia, may see long pieces of hay in the feces
What causes an left sided “apple shaped” cow
Gas accumulating at the top of the rumen causing mid-abdominal dorsal distension
What causes a right sided “pear shaped” cow
Disturbances in abomasal flow causing progressive distension of lower right abdomen
Describe a “papple” shaped cow and how this occurs
Distension of upper left abdomen and lower right abdomen, caused by gas and fluid distension of the rumen on the left and the ventral sac of the rumen pushing towards the right as it distends +/- abomasal distension on the ventral right side
What might be felt on a rectal of a cow with chronic vagal indigestion
The ventral sac of the rumen distended compared to the dorsal sac creating an “L” shape with the ventral sac eventually occupying up to 75% of the abdomen
What is type 1 vagal indigestion
Failure of eructation (free-gas)
What is type 2 vagal indigestion
Failure of omasal transport
What is type 3 vagal indigestion
Abomasal impaction
What is type 4 vagal indigestion
Partial obstruction of the forestomach compartments
What are causes of type 1 vagal indigestion
Esophageal obstruction (tumor, abscess, foreign body), inflammation adjacent to the vagus nerve. Can occur repeatedly in young calves (3-10 months) related to respiratory disease or idiopathically- usually improves over time
What are causes of type 2 vagal indigestion
Traumatic reticuloperitonitis, reticular adhesions, space occupying lesions that inhibit omasal transport or occlude the orifice
What are causes of type 3 vagal indigestion
Primary abomasal impaction (restricted water and dry coarse roughage) or secondary abomasal impaction (decreased abomasal emptying , can be related to hardware disease, perforated abomasal ulcers, lymphosarcoma, etc.). Can also be caused by foreign bodies obstructing the pylorus, but these are more commonly found in the omasal orifice.
What are the causes of type 4 vagal indigestion
Abomasum forced cranially by the uterus
What diagnostic findings are consistent with vagal indigestion
Hardware disease (elevated fibrinogen, total protein, and leukocytes), dehydration, metabolic alkalosis, hypochloremia (except in type 3), hypokalemia. Diagnosis requires exploratory rumenotomy/laparotomy.
How would you surgically approach a type 2 vagal indigestion
Left rumenotomy
How would you surgically approach a type 3 or 4 vagal indigestion
Abdominal exploratory from the right