I would serve it from the carton initially without it being refrigerated. After it is opened, it has to be refrigerated, but I don't think there should be a problem warming it up. I rescued a cat that was horribly beaten with an aluminum baseball bat (professional player from another country) and his jaws were shattered, driving his front teeth through his tongue. The vet was able to free part of his tongue so that he could lap, but he could never chew (his jaws had fused by the time I found him and surgery wasn't recommended). Anyway, the reason for this explanation is that he drank CatSip for 12 years and loved it. After it had been refrigerated, I did warm it for him (just test it like baby formula so that it's not too hot!). How wonderful you are for "warming" up an outside cat ... love and light to you. Also, if you feed the cat wet food, I would warm it as well if it has been refrigerated. If you do bedding for the cat, be sure it's straw; towels and blankets will get damp and freeze to the cat's fur. Change the straw when necessary.

I would think Catsip would be fine, we have only had one in our brood of 8 that has reacted badly, but he also reacts badly to canned food we are feeding our eldest female. Is the mother in the shelter with the kittens? She may just need an adjustment period, or she isn't comfortable with the shelter, new moms can be fussy. Thanks, Dave

Yes agree with the last comment, this is usually from stress, biting and scratching usually from fleas or allergens, owned cats for yrs, one of my little orange tabbies did that the last couple of years before she passed, they sid it was stress, she was 15 !

Per the packaging, it can be stored up to 7 days in the refrigerator after being opened.

Regular milk has additives like calcium and other vitamins which sounds good but apparently these additives which are in human milks can cause urinary track problems and crystals to form. It’s more common in male cats but a Urinary track blockage is very dangerous. I would not feed cats anything with calcium in it. 

I think your Persian cats will be fine, my kitten likes this treat a lot and she had never had any digestive issues, but she also isn't a Persian cat.

No. This milk is lactose free so it will not help with that. I would try hairball treatments like treats or the stuff you put on their paws that's sticky. This milk doesn't aid in digestion.

I would imagine it does no harm. I give my cat a container a day. She's 13. She has a sensitive stomach and it doesn't make her sick. As long as he doesn't seem to have any issues with it I don't see what it would hurt!

Does he medically need it? If not then don't worry about it. Dogs are more of broth drinkers.

I did not see any on the online list, but check by visiting the store and viewing the active and inactive ingredients.