Plastics are really amazing! They can be light or hard, easy to breakdown or very difficult! For example if Henry 8th in England wore disposable nappies they would still be in our rubbish dumps and landfill 400 years later.
The plastic bag your dog ate, probably over-whelmed its stomach and stomach juices and so was “passed” through the system rather than being digested or dissolved. This can be the bodies response to protect itself – it didn’t what to have the system blocked. It can be really dangerous as such bags can cause twists in the intestine, get caught up and need to be surgically removed. So be pleased it came out of your dog safely and of its own accord.
Am sure Mark will have some really interesting stuff to add on this one.
Great Q wombat – at last one about plastics… this Q is very related to some of the work our research group are doing, not on dogs but on marine turtles.
First up the digestion part – animals digest food using enzymes and acids, which together with the muscular action of the stomach walls, breaks down food so that the nutrients are released for uptake into the body. The main thing for plastics is that they are synthetic polymers and there no enzymes or stomach acids that can break them down quickly. Which is why, as James said, your dog passed the bag through the system. Sure if a plastic bag was to remain in the dogs stomach for many months (or maybe longer) it would start to break down – unlike food which generally takes hours or days.
Also as James said there can be problems, because they dont break down in the gut plastics can block the passage between the stomach and intestines which can then cause a build up of bacteria and gasses and then the animal gets really sick. Even the biodegradable bags are a problem because they are created to degrade under sun light not in the gut – so if an animal eats them before they degrade it can cause problems.
The other issue is that plastics are made of chemicals, and once plastic products are eaten the poisons from the plastics can leach out of the plastic and into the blood stream. This is the reason that baby bottles and drink bottles now have to be made with no BPA – which is a particularly nasty chemical. We have now found BPA in the blood taken from young sea turtles which is very frightening.
There is so much plastic in our oceans that it is causing huge issues for many marine animals like seabirds and turtles. About 35% of turtles that die in southern QLD each year have plastics in their guts. There are several youtube internet clips of the albatross in the Hawaiian islands and the impact plastic has on these birds is staggering. Take a look here http://www.midwayjourney.com/ about the albatross and if you have a strong stomach watch the film trailer. It is a pity we cant attach files as I have some good photos.
There are many things that we can do to reduce the impact of plastics – reduce use of single use plastics (i.e. those that are made for one use like straws and plastic cutlery), we can clean up our beaches and habitats and there are many groups that you can join to do this.