Sorry to hear your dog is unwell, hopefully this is something very minor, however I have worked out an answer for you ...
The drops of mucous and blood is a concern for you I know but while other diagnosis are possible where this occurs where a dog has diarrhoea then what you are seeing could be due to the rupture of a small blood vessel in the lower intestinal tract caused by the straining. If this is the cause then it is nothing to worry about and will usually resolve when the diarrhoea is resolved.
1. But be aware that this sort of thing is always a gamble so if you want to be 100% sure you are doing the right thing you should have a vet check him over without delay. That said that there are a number of home remedies for diarrhoea in the dog, these work well for uncomplicated cases where a dog is otherwise quite bright and happy as in your case, where for example a dog has eaten something he should not have out in the yard, or had some unaccustomed rich foodstuff, or has somehow acquired a minor tummy bug.
Here are some examples.
1. I am aware that some owners use Pepto-Bismol to treat their dogs with gastro-enteritis and report success. Here is a link to a web page which has all the information you might need including dose rates : LINK
2. Some owners try and control the situation with diet alone before they try anything else. This is logical and often works, the basis of this is to give the intestinal tract a complete rest and then bring it back slowly to function, resting the alimentary tract is the critical factor. It would go something like this ...
A. Starve him for 24 hours but make sure he has access to water.
B. The next day feed him four or five small light meals in the day. These meals should be the likes of chicken, fish, scrambled egg etc. with a little rice.
C. If he picks up on this diet gradually reintroduce his normal diet over the next few days.
3. Live yogurt added to the food can often help. Some gastro-enteritis situations are caused by an imbalance in the bacteria in your dog's gut. Live yogurt is full of " good " bacteria and will seed them into your dog's intestinal tract and restore the balance. You do not need to give much, a couple of tablespoons twice a day would be fine for a dog of your one's size.
Of course if any of the above does not quickly start to work or if he deteriorates further in any way you should have your vet check him over just to be on the safe side.
I hope I have covered your question fully enough but if you would like further clarification or to talk things over a bit more then I will be on-line for the next hour or so and I will be more than pleased to continue working with you.
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