Sounds like these folks may have moved up from neglecting their animals to endangering their child needlessly. Isn't it usually the way of things. Sad. Sad. Sad.
I do think it may have been the ferret. If as RKT points out they have been neglectful of their pets in the past it is entirely possible IMO that this little ferret was seeking the formula smell out of hunger.
I do not think the rot would have been responsible given the time of the incident. I would assume the baby was in bed (crib) and rot would have a harder time accessing the infant. Also, I am afraid if the rot had done it the child would likely be dead. Rots are known to be very agressive once they have clamped on and once the agression has been triggered I doubt he would have started or stopped at the fingers.
I have no problem with rots as pets but people need to realize that these animals require proper handling and training and should never be left unattended with children. The tragic results of parents' failure to do so are plaster on the news frequently.
You make a lot of valid points and based on my experience you are a hundred percent correct. I have family that owns a rottweiler but they have extensive experience with animals (horses, cows, dogs, cats etc.). That rottweiler plays with my yorkie and is very well behaved. I've seen breeds that back home are perfectly well behaving including (danes which my dad owns, german shephards which my moms side of the family breed, and even small breeds such as Schnauzers and poodles that are way agressive and not property socialized at all while walking my dog in the city). Even heard of aggressive ferrets, thought about owning one for awhile but a friend said they either make great pets or are aggressive. They said they are not a hundred percent tamed and can act out as they age. I agree if it was the rottweiler the kid would probrably be dead. These people should not be allowed to own pets based on what I have read.