It really is simpler, easier and cheaper to give the cows these magnet boluses.<p>- The magnets cost less than a dollar each once you&#x27;re buying a couple of hundred. You can outfit a herd of probably 4-500 animals for the replacement cost of one cow.<p>- It takes less than a minute to administer each one<p>- I have never seen one passed into dung or regurgitated into the feed&#x2F;bedding areas<p>A drone could perhaps scout a field, but it&#x27;s challenging terrain: 
- You are looking for metal from the size of a paperclip up to the size of a large pack of gum across hundreds of acres of land<p>- You are searching in tangled grass (or other forage crop)<p>- How will the drone collect the items? Do you want a farm worker to come and collect each piece? They can be very hard to see.<p>As someone who has experience in this area (and likes his fancy tech) I honestly believe that the current tiered state is quite effective:<p>1. Metal detectors in foraging machinery. This stops and reverses the field machinery whenever it picks up something. You hop out of the tractor and fetch out the offending article. This gets the larger items<p>2. Magnets in feeder machines. This is one hell of a magnet that sits somewhere in the machine used to dispense feed. It picks up smaller items that may have bypasses the field kit. It once took me 5 minutes to get a screwdriver unstuck when installing one of these.<p>3. Magnets in cows. The items from the linked article.<p>EDIT: The ones I have seen are caged magnets which trap any metal inside a plastic cage, further removing pointed bits. Image search for &quot;bovine caged magnet&quot; shows different types.