Seems easier, sure - but one modestly-robust drone, maybe a sort of lawnmower with caterpillar tracks, could happily roam around the pasture permanently, picking up ferrous debris and taking it back to a drop-off point for recycling.
From the tiny amout of reading I've done cows eat hardware - nails, screws, and bits of wire that are accidentally left in feed troughs, or bits of wire from tires that are left in fields for some feed product.
Many cases of hardware disease would be a oided if there was some concentration on keeping those safe for cattle.
I agree with what you said, and can add a little more context to the subject.
I have a little experience with this subject. Some of my family once a month drive through grass fields to harvest hay which is chopped and delivered to dairy farms in the area. They range from several hundred heads to ~10k heads.
The fields aren't owned by the dairy farms, they're owned by field farmers and the hay is sold to the dairy farms. So the field farmers who already use old machines have no money, and no incentive to purchase and outfit a drone to comb their fields for metal.
So once a month the fields would have to be 'combed for metal', which is hundreds of acres spread out over different locations. However this still wouldn't stop everything because you have tractors, equipment, semis and trailers going through the field every month chopping and loading hay. So I suppose you would need to have the magnets on the end of the dump and push the hay through the magnets to make sure you're catching everything. This might sound complicated and cumbersome, because it is. On top of that, these trailers also have to be used for hauling corn, potatoes, manure, and everything in between.
Even if you managed to do all that, there's still no guarantee that there won't be metal contamination between the time it's offloaded and fed to the cows.
That was a really long way of saying, it'd be nice, but it isn't practical.
...it really is much simpler to just stick a magnet in every cow.
Is it though? If you have twenty cows, sure, I can believe that twenty magnets are simple and cheap - but what about 200? 2,000? And what happens when one of your cows turns out to have a larger than usual pyloric sphincter, and the magnet gets into its intestines? Or a wider than standard trachea, leading to it regurgitating the magnet when it tries to chew the cud?
Essentially what I'm envisaging is an outdoor Roomba that just gets left to do its own thing until it needs human assistance. Arable farming - at least at the larger end of the scale - is getting pretty comfortable with drone equipment, with driverless combine harvesters guided by GPS and similar things; livestock farmers are not going to be averse to it either (not least because farmers, in my experience, really dig flashy toys! :) ).
It really is simpler, easier and cheaper to give the cows these magnet boluses.
- The magnets cost less than a dollar each once you're buying a couple of hundred. You can outfit a herd of probably 4-500 animals for the replacement cost of one cow.
- It takes less than a minute to administer each one
- I have never seen one passed into dung or regurgitated into the feed/bedding areas
A drone could perhaps scout a field, but it'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
- You are searching in tangled grass (or other forage crop)
- 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.
As someone who has experience in this area (and likes his fancy tech) I honestly believe that the current tiered state is quite effective:
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
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.
3. Magnets in cows. The items from the linked article.
EDIT: The ones I have seen are caged magnets which trap any metal inside a plastic cage, further removing pointed bits. Image search for "bovine caged magnet" shows different types.
Fortunately this is knowable because sticking magnets in cows is something that we've done for many, many years. So we know what it costs and how effective it is.
Whereas a robot to solve the problem doesn't yet exist. And the important bit here is to realize what the word "solve" means here.
I'm not saying a workable solution will never exist, but in order to be as effective it would need to be orders of magnitude better at its job than a roomba is at its job. And what the roomba does isn't very hard to begin with. You would have to cover a very large area of sometimes pretty rough terrain every N days, and you would need to have a very high success rate at both detection and removal for the solution to be able to compete with the established practices.
To understand the problem I can only recommend spending some time on a farm where they keep grazing cattle.
At $2 - $5 per magnet, (as listed on that website, you could probably get them cheaper if you're outfitting a herd of 2000+) you'd have to cut a lot of corners to build something that can traverse a populated pasture and pick up tiny bits of metal and still come out as an economical choice.
I take it you are from a US mid-west farming state that is pancake flat as far as the eye can see. Most of the corn fields where I live are neither flat nor level and are only a few hundred metres across. Even with high labour rates as they are here in Norway self driving combines are probably not an economic proposition.
As for an outdoor Roomba, well the indoor variety wouldn't work in my house so what chance is there of an outdoor one working. And yes, I am aware that I can buy some rather nice autonomous lawn mowers for suburban gardens but again they rely on a landscape designed for them.
I guess serial numbering would help get the magnets back to the right cow. But it doesn't matter if one or two come back up - you're aiming at <st>herd immunity</st> reducing the number of cows affected. Stopping most cases is good enough.
I think you're misusing the term "herd immunity". Herd immunity implies that the risk of an non-immunized individual contracting a disease is reduced because his chances of bumping into a sick individual is low.
I don't think this applies here, insofar as we're not talking about an infectious disease.
I think it's a good analog if he's suggesting that all the cows with magnets will eat up all the metal leaving little for the ones that do not have magnets. No idea if that's how it works though.
Now do the math for the drones required to sweep the land for 200 cows, say, once a month.
A spare wheel probably costs as much as a magnet.
And don't forget that the metal being ingested isn't just sitting on the surface of the grass. In many cases, it's probably buried in the first 2 or 3 cm of topsoil and being turned up as the cattle uproot the grass. Is your drone going to handle this? Is it really handling all this at a price of sub-$20 per head over 10 years? I'd have to see it to believe it.
Congratulations, you already have a semi-autonomous self-replicating metal-finding and collecting drone that also happens to produce meat and/or milk. Virtually zero additional overhead beyond the cost of the magnet.
That's great until a cow eats your drone. Then you'll need a _really_ big magnet.
This probably isn't economically feasible yet, but I'm sure we'll see something like this in the next decade or two. And for that matter, such a drone could be cutting the grass or doing other similar jobs.
I should laugh at this, but having had horses demolish the ($125 replacement cost) seat on my ATV because I was dumb enough to leave it in the pasture overnight, it hits a bit too close to home.
I've yet to encounter an animal that wasn't destructive when it got bored! Maybe goldfish?
