Sheikh Salman al-Oadah
Scholars disagree on this matter. Some claim that all animal droppings are impure. Others say that the droppings of animals that are lawful to eat are pure. Impurity is only attributed to what comes out from human beings and animals whose flesh is unlawful to eat. This is the strongest of the two opinions.
This view was adopted by Ibn Taymiyah [Majmû` al-Fatâwâ (21/542)]. He devoted a whole treatise to this topic wherein he supported this view with considerable evidence.
Source: Islam Today