Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your situation, and wanted to help.
Now just like people, when dogs can have diarrhea like this it can be caused by a range of agents. These include bacterial viral, parasitic (worms but also protozoa like Giardia, Coccidia, etc), toxins, nutritional (less likely here), and general dietary indiscretions type causes. Now I appreciate that your dogs don't not mix with other dogs but with multiple dogs affected and a lack of response to your supportive care, this does raise suspicions that you are not just seeing a benign indigestion and that there is likely an infectious cause afoot. Furthermore, the straining the lurcher is showing suggests that there is a degree of irritation/inflammation to the colon arising secondary to this diarrhea.
Now your trying a light diet was a good first step in ruling out nutritional issues and benign GI upset. As well, this is a good supportive measure to continue since light/easily digestible diets will be better tolerated and absorbed by the compromised gut and should get some nutrients in and result in less diarrhea. As well, if you aren't already, you do want to feed this as small frequent meals to further decrease the volume of diarrhea he is producing. You noted a simple carb diet but I do want to make sure you are including a protein source as well. When we feed these types of diets, we tend to use boiled chicken with rice, boiled white fish with rice, boiled lean mince with rice, scrambled eggs (made with water and not milk), or cottage cheese with rice (you can substitute rice for another starch like plain pasta or potato but we find rice is quite well tolerated by dogs). There are also veterinary prescription diets that can be used in cases of gastroenteritis (ie Hill’s I/D or Royal Canin’s sensitivity).
Furrther to this, if you are keen to try and rule out parasitic worms as a differential to cover your bases, you may want to consider worming these dogs at this time. To treat worms, you can buy worming products over the counter at your local vet or pet stores. There are a range on the market, but you want to use a good quality wormer that covers all our GI worms. In this situation, it would be ideal for you to treat with Panacur, Drontal (LINK) or Milbemax (LINK) as it will cover all the worms in question. Do make sure to have an idea of their weight before purchase wormer to make sure you get the correct dose for their size. Now since it has been a week, I do want to note that diarrhea can dehydrate a dog. Therefore, I would suggest checking their hydration statuses at this point to make sure there is no secondary dehydration on the horizon for these dogs. To check their hydration status to make sure they are not becoming dehydrated there are a few things we can test. One is whether the eyes appear sunken, if the gums are tacky instead of wet/moist, and whether there is a "skin tent" when you lift the skin. To see how to check these parameters for dehydration, you can find a wee video on this HERE. If you are seeing any signs of dehydration already, then you do want to have them seen by the vet before this makes them feel even more poorly. (since it is often the dehydration that starts to tap their energy level and actually makes them feel ill)
If you were concerned that he was becoming dehydrated, you can try and encourage drinking by offering fresh water or even low-sodium chicken broth. If they are not amenable to these, you can syringe feed pedialyte or purchase Lectaid over the counter from your vet's. These are nice alternatives to water because they will get some of those lost electrolytes back into them as well. A typical maintenance rate for hydration in an animal is 48mls per kilogram of weight a day. If you do give syringe pedialyte, this should obviously be divided up into multiple offerings through the day rather then all at once. This value will give you the total a dog needs for the day and is a good starting point to give you an idea of each dogs daily requirement. (we aren’t calculating losses, so you can add an equivalent volume to match how much diarrhea is being producing). If you cause any vomiting when you have given pedialyte, then therapy should be discontinued (since we don’t want vomiting because of our intervention).
To slow the loose feces and give a bit more 'control,' Immodium (More Info/Dose) can be used and would be a potential option here. That said, this does need to be used with caution since it would not be appropriate to use if their diarrhea was caused by a toxin, virus, or endotoxin secreting bacteria that can cause further toxicity when left to fester in the gut. This is because if we slow down GI transit when trying to slow diarrhea, we can allow these agents more time in the GI and increase the risk of the body further absorbing what it had been trying to flush out. So, if there is any chance of agents like Parvo, Campylobacter or Salmonella, we'd not want to be administer anti-diarrheals without having them checked first and these bugs ruled out.
As long as these nasty differentials are rule out, then you could choose to use Immodium. Alternatively, we will often use Protexin Pro-Fiber (example) which you can buy over the counter from your vets or Kaolin/Kaopectate (LINK) which is available over the counter at most pharmacies in preference to Immodium. That all said, anti-diarrheals will slow diarrhea (to reduce dehydration risk and nutrition loss) but we tend to use these alongside appropriate treatment since anti-diarrheals cannot cure diarrhea alone.
Overall, there can be many triggers for diarrhea of this nature. Your initial steps to address the diarrhea were good but the recurrence and the fact we have multiple dogs affected really raises concerns that you are dealing with an infectious agent here. Therefore, do continue your supportive measures (via light diet and maintaining hydration) and if they haven't been wormed recently, you can consider addressing this as well. That said, if their signs do not settle, then it would be worth following up with their vet. If you aren't keen to take them in just yet, then you can consider taking a fresh fecal sample to the practice to be sent to the lab. This can be checked for common parasitic, protozoal, viral, and bacterial causes of diarrhea. Depending on the findings, you will be in a position to identify the agent to blame, to treat it effectively and clear this abnormal stool to get them back to normal. Just in case you don't yet have a vet in your new area, you can find one near you via the RCVS Register (HERE)
I hope this information is helpful.
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All the best,
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