For most species, chaya must be processed in some fashion to release the anti-nutritive (toxic) hydrocyanic glucosides. Chickens seem to tolerate raw leaves, possibly because of the cell walls being crushed in their crop and the volatile toxins released before digestion occurs. Other monogastrics (such as pigs), should not be given raw chaya, in principle.
Ruminants usually will not eat raw leaves because of the toxic compounds, so processing is almost always required in order to incorporate into their diet. Ungulates (like the antelope mentioned in one post) tend to deal with the issue through their browsing habit–not eating more than the body can detoxify itself.
As for processing, there are many methods that range from drying and crushing into a protein leaf powder, boiling (for five minutes; then maybe drying and processing), and some extraction techniques that are a bit more high tech. The basic principle, though, is to crush as many cell walls as possible for the volatile glucosides to dissipate.
Hope this helps!