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It is unlikely that your dog will experience any adverse effects from eating the cockle burr. The acid and enzymes of the gastrointestinal tract will soften and most likely digest the cockle burr and it should pass in the stool uneventfully.
If it were to cause a problem, it may result in an obstruction of the bowel. This would cause your dog to feel very ill acutely and cause excessive vomiting. These are the things you can watch for.
I hope this information helps. Please let me know if I can be of further assistance.
Give him a little time and some water if he will drink. If you think it is still stuck after 30 mins to an hour you probably need to have him examined by your vet. It should pass with time. If your dog can breath ok and eat and drink you know that it is not stuck.
Let me know if I can be of more help.
Great! He should be just fine.
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