In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu `alaykum wa-rahmatullāhi wa-barakātuh.
It is not permissible to use zakat for the treatment of injured animals.
Zakat is to be paid to a humanbeing who is a Muslim and who is poor and needy as defined by Shariah. [i]
And Allah knows best.
Mufti Saeed Ahmed Golaub
Islamic Solutions
Jamaica
[i]مشكاة المصابيح (1 / 570):
وَعَن ابْنِ عَبَّاسٍ قَالَ: فَرَضَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ زَكَاةَ الْفِطْرِ طُهْرَ الصِّيَامِ مِنَ اللَّغْوِ وَالرَّفَثِ وَطُعْمَةً لِلْمَسَاكِينِ. رَوَاهُ أَبُو دَاوُد