The answer to my question is at least ten percent if it has less than that the United States does not recognize it as ice cream.
In the U.S., there are federal standards[2] for butterfat content of dairy products.[3][4][5][6] Commercial products generally contain the minimum legal amount of fat.
* Milks
o skim milk contains less than 0.5% fat, typically 0.1%
o whole milk contains at least 3.25% fat
* Cheeses
o dry curd and nonfat cottage cheese contain less than 0.5% fat
o cottage cheese contains at least 4% fat
o Cheddar cheese contains at least 50% fat relative to the total solids
o Swiss cheese contains at least 43% fat relative to the total solids
* Frozen desserts
o ice cream contains at least 10% fat
o lowfat ice cream, also called ice milk, contains not more than 2.6% fat
* Creams
o heavy cream contains a minimum of 36% fat
o manufacturer’s cream (not federally regulated) contains 40% fat
* Butter (including whipped butter) contains at least 80% fat
Hows that for hijacking a thread!