Bloat refers to the acute swelling or distension of the rumenoreticulum, and has significant economic and welfare impacts on the cattle industry.
Clinically, it is noted as a profound distension of the left side of the abdomen, and associated with dyspnea. Many cattle die from asphyxiation unless the bloat is not resolved by eructation (burping), or by manual or surgical alleviation of the gas or fluid.
Causes in cattle include:
- Secondary to other diseases which cause lateral recumbency, e.g. tetanus
- Ingestion of rich pasture - e.g. clover, sweet potatoes, carrot, high-gran diets.
- Bovine leukosis
- Genetic predisposition - Jersey cows more prone
- Lateral recumbency as a consequence of sedation/anaesthesia
Frothy bloat is caused by fermentation of legume or legume-dominant pastures, particularly alfalfa, ladino, and red and white clovers, but also is seen with grazing of young green cereal crops, rape, kale, turnips, and legume vegetable crops. Frothy bloat also is seen in feedlot cattle, and less commonly in dairy cattle, on high-grain diets.
Gas bloat is usually caused by a mechanical obstruction to normal gas release via eructation. This is commonly seen with foreign bodies such as potatoes, apples and turnips. Secondary obstructions can also occur with tetanus, vagal indigestion, diaphragmatic hernia, traumatic stenosis, lymphadenopathy (Bovine leukosis) or if the cow is cast in lateral recumbency and is unable to sit up.
Bloat can affected cattle of any age. Often dietary-induced bloat occurs frequently on particular farms and historical evidence helps support a suggestion of the disease. Because of the variety of inducing causes, clinical signs are not a diagnosis per se, and the underlying causes usually require investigating.
In most affected cows, clinical signs include a visibly distended left side of the abdomen, dyspnea due to mechanical interference with breathing, pallor, kicking at abdomen with hindlegs, and in severe cases, circulatory shock and death. It is not unusual in acute cases of legume poisoning to have outbreaks of bloat within a single herd.
Clinical diagnosis of is based on presenting signs and response to relieving the bloat.
Most cases should be treated as medical emergencies. The passage of a stomach tube or trocarization releases large quantities of gas and alleviates distention. A rumenotomy should be performed if large obstruction are present (e.g. large quantities of carrots, turnips, etc).
A variety of antifoaming agents are effective, including vegetable oils (eg, peanut, corn, soybean) and mineral oils (paraffins), at doses of 250-500 mL. Dioctyl sodium sulfosuccinate (docusate), a surfactant, is commonly incorporated into one of the above oils and sold as a proprietary antibloat remedy, which is effective if administered early.
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- Merck Vet Manual