Kevin Robertson, [26 Jan 2024 at 20:47:04]: Good afternoon colleagues - some advice please. We have just had a 15-month African buffalo bull swallow a 3 cc Pneudart with a 3/4” needle. The cow he was with was darted and he immediately bit out the dart and swallowed it. We are sure of this because he was also darted to check his mouth / throat but there was no sign of it so the conclusion is that it was swallowed. The local vet wants to take a wait and see approach. Such incidents are very rare here in Texas so please offer some suggestions. Many thanks. Ian Parsons, [26 Jan 2024 at 20:57:42]: The least invasive but still proactive measure would be to dose a bovine rumen magnet. Steel needle should be pulled onto it and it will disintegrate with time. David Pretorius, [26 Jan 2024 at 21:03:41]: The needle is made of stainless and the head of aluminium. Both metals are not attracted to magnets. The needle will not penetrate beyond 3/4" - my guess is this already happened due to the rumen motility and length of dart. I think the only option if you want to intervene is a rumenotomy. On the other hand, buffalo immune systems are well developed so nothing may happen as well. An option some have opted for in herds where they regularly pull darts is a double wire needle. They are exceptionally strong and can't get them out. Ian Parsons: Maybe different materials 🤷🏼♂️ David Pretorius, [26 Jan 2024 at 21:19:17]: Maybe I always assumed they would use a medical grade stainless? That is a strong attraction. Magnet definitely a preferred option then. (Ed :Some background on stainless steel from David Pretorius below: ) Stainless steel's magnetic properties vary based on its composition and microstructure. In general, there are several types of stainless steel, each with different magnetic characteristics: 1. Austenitic Stainless Steel (300 Series): This type is typically non-magnetic. It contains high levels of chromium and nickel, and low levels of carbon. Common grades like 304 and 316 fall into this category. The austenitic structure is formed at high temperatures and retained at room temperature, which contributes to its non-magnetic properties. 2. Ferritic Stainless Steel (400 Series): Ferritic stainless steel is usually magnetic. It contains higher levels of chromium, but little or no nickel. Its structure is similar to that of carbon steel, which contributes to its magnetic properties. 3. Martensitic Stainless Steel: This type is also generally magnetic. It is similar to ferritic but can be hardened by heat treatment. It has moderate corrosion resistance and is often used in applications where strength and hardness are more important than corrosion resistance. 4. Duplex Stainless Steel: Duplex stainless steels have a mixed microstructure of austenite and ferrite, which gives them a blend of properties. They tend to be partially magnetic, but less so than ferritic or martensitic stainless steels. 5. Precipitation Hardening (PH) Stainless Steels: These are generally magnetic. They are made to be exceptionally strong by a process of heat treatment and are used in applications where high strength is required. The magnetic permeability of a material, which is a measure of how well a material can support a magnetic field, is another important factor. For instance, even though austenitic stainless steel is generally considered non-magnetic, it can become slightly magnetic when cold worked, like during bending, forming, or machining, due to changes in its microstructure. In summary, whether stainless steel is magnetic depends on its specific alloy composition and the processing it undergoes, with ferritic, martensitic, and PH stainless steels being generally magnetic, while austenitic and duplex stainless steels are usually less magnetic or non-magnetic. Medical is usually 316L
