The Vishnu Smriti condemns bestial acts:
Causing (bodily) pain to a Brāhmaṇa; smelling at things which ought not to be smelt (such as excrements), or at spirituous liquor; dishonest dealing; sexual connection with cattle, and (sexual connection) with a man (or non-vaginal intercourse with a woman): such are the crimes resulting in loss of caste. He who has knowingly committed one of the acts effecting loss of caste shall perform the Sântapana penance; he who has done so unawares shall perform the Prâgâpatya penance. (Vishnu Smriti, Chapter 38, Verses 1-6)