Yogurt is a cultured milk product wherein Lactobacillus acidophilus bacteria have been added to the milk in order to aid in the digestion of lactose (milk sugar). Lactose intolerant people and most animals do have problems with milk and milk products, but the majority of them can safely consume yogurt made using live bacteria cultures.
There's a lot of info on the usefulness of yogurt at
Live, Active and Probiotic: The Yogurt Culture
By Pat Kendall, Ph.D., R.D. Food Science and Human Nutrition Specialist Colorado State University Cooperative Extension
"The claim most substantiated is yogurt's beneficial effect on digestion in some individuals. People who are lactose intolerant have a hard time digesting milk products because they lack the enzyme that breaks down the main carbohydrate in milk. Yogurt is a unique dairy food because the starter cultures actually produce that enzyme during fermentation. Thus, the milk sugar in yogurt is more easily digested, even for lactose-intolerant individuals. Many people who commonly experience gas, bloating or discomfort from dairy foods can digest yogurt more easily, thanks to the starter cultures. This is especially true if the yogurt contains live cultures. Claims regarding the usefulness of probiotics in reducing the risk of intestinal infections also seem to have some merit. Studies have shown, for example, that children suffering from chronic diarrhea recover faster when fed yogurt with probiotic cultures. Adults suffering from traveler's diarrhea also seem to benefit. Scientists attribute this to probiotics' apparent ability to create an acidic environment that inhibits harmful bacteria."
Granted, it is geared towards human consumers, but the basics of digestion are the same in reptiles. The Lactobacillus acidophilus bacteria convert the lactose to a more digestible form for reptiles as well as us. I've used it for treats, tonics after medication, as a supplement for recovering reptiles and the base for bug slurry for sick reptiles who aren't eating on their own (never used on a snake, so I have no clue how/if it works with them). If I'd noticed any problems digesting the yogurt or slurry, I would have stopped using it years ago. There's never been any sign of discomfort, diarrhea or other negative signs or symptoms. If anything, I can credit the yogurt for saving at least a dozen gecko and cham lives in either my collection or rescues I took in.
I've fed it to sickly weak and thin leopard geckos, some of whom had lost weight to almost nothing before the (former) owners smartened up and got them treated for intestinal parasites. It's also great for sick leos (and other geckos) who can't or won't hunt bugs. I've noticed a definite weight gain in most leos within a week, at most a couple of weeks. Of course, like anything else, some geckos just don't improve, so don't think I'm passing this off as a cure-all, but it sure does work wonders in most sick geckos, and the nutrition it supplies is fantastic. Part of the charm of the yogurt is the live bacterial culture. The Lactobacillus acidophilus is one of the bacteria naturally occuring in the gut. If you check the ingredients on some tonics like Probiotics, you'll see it listed there. Basically, the live culture yogurt helps replenish some of the natural bacterial fauna that might be lost or insufficient in sick animals due to any number of things including side effects of medication.
If you check the ingredients in Acidophiliz+ you'll see the same Lactobacillus Acidophilus listed as in live culture yogurt.
Pet Authority Acidophiliz+
Product Ingredients
Triple Filtered Spring Water
Lactobacillus Acidophilus Cultures
Yucca Shidigera
Papaya Puree
Calcium
Vitamin A
Vitamin B1
Vitamin B2
Vitamin B6
Vitamin B12
Vitamin C
Vitamin D3
Vitamin E
Factor in that yogurt also has other nutrients such as protein, I'd say that yogurt is much better in the long run.
When I retire, I plan to sleep between naps.