Take four horse-crazy little girls, add some recently rescued horses in need of funds for foster care, toss in some youthful ingenuity and what do you get? How about a quartet of kids going door-to-door to collect money for the abused horses’ care. That’s what happened recently when Serena Thorn,10, of Loudonville, N.Y., read a story in the Times Union on Dec. 23. The article told about the plight of eight neglected horses being cared for at nearby Little Brook Farm. After visiting the horses themselves, Thorn and three of her friends went to work. They created a poster showing photos of the horses, including poor old Paxton, a blind equine senior citizen who’s being nursed back to health. Plus, they displayed the article from the newspaper. Ultimately, the girls raised more than $500, which they presented to the farm on the horses’ behalf.