Back from the Vet: Rumen Disorders in Goats
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Goats, like sheep and cattle, are ruminants. That classification is based on their method of food digestion. All ruminants break down food through fermentation in a large vat-like organ called the rumen. The rumen is food’s first stop after being chewed and swallowed. It is populated with a large variety of microorganisms that assist in food digestion. These microorganisms are what allow ruminants to break down the complex starches of forages into usable energy for the animals. The health of the rumen, and its microbes, are essential for the health of the animal.
As the rumen is a fermentation vat, one of its byproducts is gas. When gas production is normal, and the animal is otherwise healthy, they are able to eructate, or burp-up, the gas. When the animal is experiencing certain health issues or there is abnormal gas production, then bloat of the rumen can occur. There are two different types of rumen bloat — free gas bloat and frothy bloat.
Certain food substances, when digested by rumen microbes, produce a stable froth. Feeds known to produce this froth include alfalfa and certain cereal grains. Over-consumption of those feeds results in increased froth. As the gas is trapped within froth bubbles, the animal is unable to burp it out normally, resulting in frothy rumen bloat.
Free gas bloat occurs when there is dysfunction of the rumen or an obstruction preventing the normal expelling of gas. Animals with choke, or obstruction of the esophagus, can experience free gas bloat. Free gas bloat can also occur when an animal is stuck in an abnormal position, preventing burping, such as when cast upside-down. The vagus nerve, which controls rumen function, can be damaged resulting in gas bloat. This damage can be due to abscesses and tumors, as well as chronic inflammation caused by pneumonia or peritonitis. Hardware disease, or traumatic reticuloperitonitis, can also lead to free gas bloat, as the foreign body or hardware causes severe inflammation. Hypocalcemia, or milk fever, can lead to free gas bloat as calcium is essential for normal muscle and nerve function. As there can be a myriad of causes for free gas bloat, animals must be examined thoroughly to identify the cause.
Bloat itself is generally very easy to identify. Affected animals have abdominal distension on the left side, particularly notable in the paralumbar fossa. If the bloat is severe, they may also have difficulty breathing, as the rumen compresses the chest. If the dietary history of the animal is well known, it may be easy to determine the cause of bloat. Passing a stomach tube, however, is also an easy way to determine free gas vs. frothy bloat. Stomach tube passage will easily allow the passage of free gas; however, froth is difficult to remove. If you are an experienced goat owner, passage of a stomach tube may be within your wheelhouse of skills. If, however, you are not, consulting your veterinarian for emergency care is advised. Bloat can progress rapidly and lead to death, as animals are unable to breath normally with the rumen distended. Stomach tube passage, in addition to discerning the cause of bloat, also allows for administration of substances to break up froth, such as detergents or mineral oil. In animals experiencing choke, the stomach tube should not be forced down aggressively if the choke does not resolve easily. This can result in esophageal damage. In some instances, the passage of a stomach tube is not possible or not successful. In those cases, trocharization, or rumenotomy, can be performed, opening the rumen from the side of the abdomen.
In the case of frothy bloat, limiting feedstuffs known to produce froth is the mainstay of prevention. These feeds include alfalfa, clover, and certain cereal grains like corn and barley. Ideally, small amounts of these feeds should be offered at any time. When it is necessary for animals to consume greater amounts of these feeds, using supplements to prevent froth, such as bloat blocks, can decrease the risk of bloat occurring. In the case of free gas bloat, the bloat should be relieved first, and then the cause of bloat can be investigated.
The rumen, as a fermentation vat, can also be affected by differences in pH. Different microbes prefer different pH. The microbes that digest simple starches and sugars prefer a more acidic environment, and those that digest complex carbohydrates, such as those found in roughages, prefer a more neutral environment. The digestive system of a ruminant is designed to prevent acidosis, or over production of acid by the rumen microbes. When food is chewed by the animal, they produce large amounts to saliva, which is an alkaline substance. Saliva begins the breakdown of feed and buffers the acid produced by rumen microbes. When a ruminant over-consumes simple carbohydrates and starches, overproduction of acid occurs. This acidic environment kills many rumen bacteria, and can result in fluid accumulation, rumen lining irritation, and toxemia — as dead microbes release endotoxin.
Rumen acidosis can be acute or subacute. Acute acidosis occurs when a large amount of grain is consumed. This can be when the animal breaks into the feed bin, or the diet is too heavy in grains. Acute acidosis is severe and can result in sudden death. If an animal is found to have eaten large amounts of grain, it is recommended to contact your veterinarian immediately. Animals can show signs of acidosis in the first few hours to days of consumption of the feed. They experience diarrhea, bloating, and shock. Subacute acidosis can be more difficult to identify. Animals can experience intermittent anorexia and diarrhea, and be otherwise fairly healthy.
Treatment of acute acidosis requires intensive care. The animals often require intravenous fluid support and antibiotics. If the animal survives the acute phase, steps can be taken to re-supply the rumen with healthy microbes. If animals are identified shortly after eating large amounts of grain, your veterinarian may be able to remove the feed and prevent acidosis. Subacute acidosis is more difficult to identify. Your veterinarian can test blood and rumen contents to identify if this is the cause for an animal’s poor performance.
Prevention of acidosis involves maintaining a properly balanced diet. Goats and other ruminants should ideally be offered roughage feeds free-choice. The addition of too much concentrate, or the addition of a concentrate feed too rapidly, will upset the balance of microbes within the rumen. If you are not experienced in feeding goats, a good rule of thumb is to ensure that no more than one quarter the total diet of the goat be a concentrate feed. When planning to feed larger amounts of concentrate, a small amount should be fed initially, and increased slowly over the course of several weeks. Breaking larger amounts of grain into smaller more frequent feedings can also help prevent acidosis. Concentrates can be very helpful in increasing health and production of goats, but care must be taken to ensure they are fed appropriately. As you design or change your feeding program, it is always helpful to consult a nutrition specialist. Your herd veterinarian is always a great resource, and many of the major feed companies also have a nutrition specialist available for questions.
Dr. Katie Estill DVM is a veterinarian consultant for Goat Journal, Countryside & Small Stock Journal, and Countryside online. She works with goats and other large livestock at Desert Trails Veterinary Services in Winnemucca, Nevada.
Originally published in the July/August 2020 issue of Goat Journal and regularly vetted for accuracy.