You are each entitled to the annual exclusion amount on the gift. Together, you can give $22,000 to each donee (2002-2005) or $24,000 (2006-2008), $26,000 (2009-2012) and $28,000 on or after January 1, 2013 (including 2014, 2015, and 2016). Refer to Form 709 (PDF), 709 Instructions and Publication 559.
This can be difficult to stop, and it is highly recommended that such cats are spayed as part of the treatment. Early spaying In the United States, most cats are spayed between 5 and 8 months of age. Many animal shelters and veterinarians are starting to spay female animals at a younger age, even at 2 months. This early neutering does not affect the growth rate, and there are no appreciable differences in skeletal, physical, or behavioral development between those animals neutered early than those neutered at a more traditional age.
They have to be at least 8 weeks old to be spayed or neutered. It doesn't have to be done so early, but it should be done sooner rather than later, as studies have shown that cats that are spayed/neutered later are at greater risk for certain serious conditions and diseases, such as breast cancer.