Large Animal Anatomy Refresher Flashcards
What is the relationship between the stomachs of a cow? Review what happens anatomically in a clinical case with LDA?
Ruminant stomachs have four compartments: the rumen, the reticulum, the omasum and the abomasum.
Rumen microbes ferment feed and produce volatile fatty acids, which is the cow’s main energy source. Rumen microbes also produce B vitamins, vitamin K and amino acids.
In calves, the esophageal grooves allows milk to bypass the rumen and directly enter the abomasum. Rumen development occurs following a change in diet and microbial growth
What is the rumens function?
Where is it located?
The rumen (on the left side of the animal) is the largest stomach compartment and consists of several sacs. It can hold 25 gallons or more of material depending on the size of the cow. Because of its size, the rumen acts as a storage or holding vat for feed.
Aside from storage, the rumen is also a fermentation vat. The rumen’s environment favors the growth of microbes. These microbes digest or ferment feed within the rumen and make volatile fatty acids (VFAs). The rumen absorbs most of the VFAs from fermentation.
A good blood supply to the rumen walls improves absorption of VFAs and other digestion products. Tiny projections (papillae) line the rumen, which increases the rumen’s surface area and the amount it can absorb
What is the reticulums function?
Where is it located?
The reticulum is a pouch-like structure in the forward area of the body, close to the heart. The tissues in the reticulum form a network similar to a honeycomb. A small tissue fold lies between the reticulum and rumen, but the two aren’t separate compartments. Together they’re called the rumino-reticulum.
Heavy or dense feed and metal objects eaten by the cow drop into this compartment. Nails and other sharp objects may work into the tissue and cause “hardware disease.” You can use magnets to prevent disease or correct the problem through surgery. Leaving it untreated may lead to infection and possibly death.
What is the function of the omasum?
The omasum is a globe-shaped structure containing leaves of tissue (like pages in a book). It absorbs water and other substances from digestive contents. Feed material (ingesta) between the leaves will be drier than ingesta found in the other compartments.
What is the function of the abomasum?
The abomasum is the only compartment lined with glands. These glands release hydrochloric acid and digestive enzymes, needed to breakdown feeds. The abomasum is similar to a non-ruminant stomach.
What are some causes of a displaced abomasum?
Two main causes of the condition have been identified:
calving: the majority of cases occur soon after calving. During pregnancy the uterus displaces the abomasum so that after calving the absomasum has to move back to its normal position, increasing the risk of displacement.
atony (lack of normal muscle tone) of the abomasum: if the abomasum stops contracting and turning over its contents, accumulations of gas will occur and the absomasum will tend to move up the abdomen.
What are the clinical signs of a displace abomasum?
inappetance, milk yield drop and reduced rumination are the most common signs.
there can be diarrhoea, mild colic and a distended abdomen.
if torsion (twisting) occurs - a problem more common in Right Displaced Abomasum - shock, low temperature and a high heart rate will occur.
Normally - just like ketosis - ketones will be present in blood, milk, breath and urine.
How can you prevent and control a displaced abomasum?
Of the two causes above, only atony of the abdomen is preventable:
- ensure cattle are not too fat at calving
- feed high quality feeds, with good quality forage
- feed a total mixed ration as opposed to concentrates
- ensure plenty of space at feeding sites
- minimise changes between late dry and early lactation ration
- prevent and promptly treat diseases such as milk fever, metritis, toxic mastitis and retained fetal membranes which reduce feed intake
- maximise cow comfort, minimise stress
Treatment for the condition can be conservative or surgical.
Conservative treatment involves casting the cow, rolling and manipulating the abomasum to return it to its normal position; this is particularly effective in early diagnosis. The animal should be examined 48 hours later to ensure that a relapse has not occured. This treatment can be used in conjunction with toggling, where a toggle is passed through the skin into the abdomen and twisted, fixing the abomasum in the correct place; this significantly reduces the relapse rate.
Many surgical techniques exist, all of which produce similar results.
With careful reference to the anatomy, what happens in a cow with bloat?
Bloat is simply the build up of gas in the rumen. This gas is produced as part of the normal process of digestion, and is normally lost by belching (eructation). Bloat occurs when this loss of gas is prevented. There are two sorts of bloat. The least common type is gassy bloat, which occurs when the gullet is obstructed (often by foreign objects such as potatoes) or when the animal can’t burp (such as with milk fever or tetanus). The second type of bloat is frothy bloat, which happens as the result of a stable foam developing on top of the rumen liquid, which blocks the release of the gas. This is by far the most common form of bloat, and unlike gassy bloat, it is highly seasonal with peaks in the spring and autumn. This is because the foam is formed by breakdown products from rapidly growing forages (particularly legumes such as clover and alfalfa). These increase the viscosity (stickiness) of the rumen fluid and prevent the small bubbles of gas formed by rumen fermentation from coming together to form free gas that can be belched off.
What are the clinical signs of bloat?
- Distended left abdomen is the most obvious sign
- Usually associated with pain, discomfort, and bellowing.
- Death can occur within 15 minutes after the development of bloat
- Gaseous bloat is usually seen in one or two animals. Frothy bloat can affect up to 25% of animals in a group
- In some cases sudden death may be the first sign seen by the stockman, although in such cases it is likely that there will be other cattle with bloat that are still alive
What is the diagnosis for bloat?
On the clinical signs described above
History of access to lush pasture, particulary if it is clover-rich
Passing a stomach tube will distinguish between gassy and frothy bloat. If it’s gassy bloat a stomach tube passed into the rumen will allow the gas build-up to escape through the tube. No such gas is seen in frothy bloat.
What is the treatment for bloat?
Passing a stomach tube is the best treatment for gassy bloat. Once the gas has been released, the cause of the obstruction should be looked for.
In a few cases a trochar and cannula punched through the side into the rumen will relieve gassy bloat when a stomach tube has not worked. But such cases are rare, and as the trochar provides a tremendous opportunity for introduction of infection, it should only be used as a last resort.
For frothy bloat, antifoaming agents that disperse the foam should be given by stomach tube. There are many old-fashioned remedies which can have some benefit but newer treatments such as dimethicone or polaxolene are easier to give as the effective dose is much smaller.
If an outbreak of frothy bloat occurs all cattle on that pasture should be removed immediately and put onto a high fibre diet (hay or straw), and any cows showing bloating signs treated with an anti-foaming agent. The pasture should not be grazed for at least ten days.
How can you prevent bloat?
It is much more effective to prevent bloat than treat affected animals. Management and planning can significantly reduce the number of cases. To prevent frothy bloat:
- If possible avoid using high-risk pastures at high-risk times. Pastures with a history of bloat problems or with a high clover content should not be used for cows soon after turnout.
- Stagger turnout with buffer feeding as this will allow the rumen to adapt to the new diet. In particular try and keep up fibre intakes at risk periods.
- If you have to use high-risk pastures, introduce the cattle to them slowly. In some cases restricting access to as little as ten minutes per day at the start may be necessary to prevent bloat.
- Avoid starting to graze high-risk pastures when they are wet.
- Administer anti-foaming agents daily if bloat is a severe problem. If this is the case and you can strip graze then spraying antifoaming oils (emulsified with water) onto the grass can significantly reduce labour costs.
- Remove high-risk animals. Some animals have recurrent bloat despite prevention and treatment.
What are the common sites of impaction in a horse with colic?
What are some causes?
Most colonic impactions occur in the large colon, particularly at the pelvic flexure and right dorsal colon. Impactions arise most commonly at sites where there is transition of intestinal movement, at sphincters between different segments of intestine, or at regions of intestinal narrowing. The causes in many cases remain unknown but possibilities include:
- Poor teeth and thus poor mastication of food.
- Stress associated with transport, etc.
- Inadequate or inappropriate food (coarse roughage).
- Parasitism.
- Systemic dehydration.
- Eating of bedding or other inappropriate material that is poorly digested.
- Gastric ulceration, intestinal adhesions.
- Lack of sufficient water.
- Sudden change in management, especially exercise or diet.
How can you identify the area of impaction in a horse with impaction colic?
Rectal exam
- The commonest colonic impaction (pelvic flexure impaction) is identified by the palpation of a characteristic firm visceral mass in the ventral left or midline of the abdomen, usually pushing up into the pelvis. It feels somewhat like the point of a flexed human elbow. Much of the left ventral colon becomes impacted and is palpable. Severe cases may lead to complete colon and cecal distention.
- Small colon impaction should be palpable as a narrower firm filled tube in the caudal ventral abdomen.
- Right dorsal colon is often impacted with left colons but is more difficult to palpate towards the mesenteric root. Gas distention is often present with the latter.
- The character of the impaction may be assessed by palpation, straw or bedding impactions feel harder and firmer. Sand impactions may be indented, and sand will also often be present in the rectum.
