Currently only 14 airlines are required to report incidents involving any animal, but as of January 1, 2015, that number will increase to 27. The new legislation also covers animals in commercial shipments, which means the DOT will collect data on dogs shipped by breeders.
Last year, the DOT reported a total of 42 incidents involving animals, down from 58 in 2012. However, because airlines seem to underreport pet incidents, it's hard to have confidence in those numbers.
While the system is far from perfect, reporting more of this information can only be beneficial to traveling animals. I always assumed the law tracking pets included all animals and was shocked to learn that an injury, loss, or death could go unreported. I hope that the stricter requirements will encourage airlines to develop safer ways to transport animals.