# Trocar Cows (DD-585) > Bloat, or ruminal tympany, is overdistension of the rumen and reticulum with the gases of fermentation. The Merck Veterinary Manual describes two forms. In frothy (primary) bloat, gas is trapped in a stable foam mixed with the rumen contents, often on legume pasture, and the usual treatment is an antifoaming agent given by tube. In free-gas (secondary) bloat, gas collects above the contents because something, such as an esophageal obstruction, stops the cow from belching it up. Free-gas bloat is quickly relieved by passing a stomach tube or by inserting a trocar and cannula through the left flank into the rumen. A standard trocar is often too narrow to let stable foam escape, and a life-threatening case may need an emergency rumenotomy. The gas itself is mostly carbon dioxide: a 1974 review gives 45 to 70% CO2 and 20 to 30% methane, and a 1997 study of grazing dairy cows measured about 65 to 76% CO2 and 22 to 31% methane. The methane is why the escaping gas can be lit. The footage shows a cannula in a cow's flank with the gas burning as a blue flame. Lighting it is a demonstration, not part of the treatment. - Department: Nature (also Science) - First published: 2025-05-31 - Last updated: 2025-05-31 - Permalink: https://detailenjoyer.com/case/trocar-cows/ - Author: Marcus Easterling (DetailEnjoyer), The Detail Department ## Quick facts - **DD-585-F01**: A trocar and cannula are used to relieve free-gas bloat. _(Write-up · Exhibit B (Where the trocar fits))_ - **DD-585-F02**: Rumen gas is mostly carbon dioxide, with methane second. _(Write-up · Exhibit C (Mostly carbon dioxide))_ ## Write-up A cow, a tube and a flame. Rumen gas is mostly carbon dioxide, with methane second. 1. **Two kinds of bloat**: Frothy bloat traps gas in foam. Free-gas bloat traps it above the rumen contents. 2. **Where the trocar fits**: A trocar and cannula relieve free-gas bloat. Frothy bloat usually needs antifoaming agents. 3. **Mostly carbon dioxide**: Rumen gas is roughly 45 to 76% carbon dioxide and 20 to 31% methane. 4. **Why it burns**: The methane in the gas is flammable, so the escaping gas can be lit. 5. **Last resort**: When a cannula fails in a life-threatening case, vets may perform an emergency rumenotomy. ## Related case files - [Sheep Dipping (DD-602)](https://detailenjoyer.com/case/sheep-dipping/): I paired it with another livestock health practice - [Bos Gaurus (DD-685)](https://detailenjoyer.com/case/bos-gaurus/): I linked a wild relative of domestic cattle ## Reel vs. record - **Note**: 'Gas from the bowels of cows': the gas is in the rumen, the largest chamber of the stomach, not the bowels. The trocar goes through the left flank into the rumen. - **Note**: 'Primarily methane and carbon dioxide': I'd flip the order. Carbon dioxide is the larger share, about 45 to 76%, and methane is about 20 to 31%. The methane is what burns. - **Missing**: the trocar works for free-gas bloat. In frothy bloat, the gas is locked in a stable foam that a standard trocar can't drain well, so vets use antifoaming agents and, in the worst cases, an emergency rumenotomy. - **Note**: My Reel vs. Record note: lighting the gas, as in the footage, is a demonstration, not part of the treatment. ## Video: Trocar Cows: A Cow, a Tube and a Flame - Duration: 26.0 s · Published: 2025-05-31 - File: https://detailenjoyer.com/assets/videos/DKVpsvGxUKG.mp4 ### Transcript DID YOU KNOW? Draining flammable gas from the bowels of cows is an emergency veterinary procedure used to relieve life-threatening pressure caused by ruminal tympany, or bloat. In ruminant animals like cows, fermentation of ingested feed in the rumen produces large amounts of gases, primarily methane and carbon dioxide. Under normal conditions, cows expel these gases by burping, or eructation, but blockages or diet imbalances can trap gas, causing the rumen to expand dangerously. NOW YOU KNOW! ## Questions & answers **Q: What traps the gas in frothy bloat?** A: It's mixed in with the rumen contents. _(Source: Write-up · Exhibit A (Two kinds of bloat) · Merck Veterinary Manual: Bloat in Ruminants)_ **Q: Which kind of bloat does a trocar and cannula relieve?** A: Foam is usually too thick for a standard trocar. _(Source: Write-up · Exhibit B (Where the trocar fits) · Merck Veterinary Manual: Bloat in Ruminants)_ **Q: Which gas makes up the biggest share of rumen gas?** A: Roughly 45 to 76%. _(Source: Write-up · Exhibit C (Mostly carbon dioxide) · Clarke & Reid, Foamy Bloat of Cattle. A Review, Journal of Dairy Science (1974); Moate et al., Rumen gases and bloat in grazing dairy cows, Journal of Agricultural Science (1997))_ **Q: Why can the escaping gas be set alight?** A: Methane is flammable. _(Source: Write-up · Exhibit D (Why it burns) · Clarke & Reid, Foamy Bloat of Cattle. A Review, Journal of Dairy Science (1974); Moate et al., Rumen gases and bloat in grazing dairy cows, Journal of Agricultural Science (1997))_ **Q: What can vets do when a cannula fails in a life-threatening case?** A: It opens the rumen directly. _(Source: Write-up · Exhibit E (Last resort) · Merck Veterinary Manual: Bloat in Ruminants)_ ## Sources - [Merck Veterinary Manual: Bloat in Ruminants](https://www.merckvetmanual.com/digestive-system/diseases-of-the-ruminant-forestomach/bloat-in-ruminants) - [Clarke & Reid, Foamy Bloat of Cattle. A Review, Journal of Dairy Science (1974)](https://doi.org/10.3168/jds.s0022-0302(74)84964-7) - [Moate et al., Rumen gases and bloat in grazing dairy cows, Journal of Agricultural Science (1997)](https://doi.org/10.1017/s0021859697004930) ## Cite this case file Easterling, Marcus. "Trocar Cows." The Detail Department (DetailEnjoyer), case file DD-585, last updated May 31, 2025. https://detailenjoyer.com/case/trocar-cows/