There is mention of an interesting halakhic ruling in an otherwise pedestrian Ynet article about abuses surrounding the practice of kapparot – the pagan ritual of waving a chicken over ones head to symbolically cast ones sins into the chicken, followed immediately by watching as the chicken is slaughtered, is meant to promote teshuva, repentence. While it may very well do that, especially for those who have never witnessed animal slaughter, if done incorrectly it causes great suffering to the animals, but not becuase of defective slaughter. Chickens are normally transported and housed crammed in small cages. They don't have room to spread their wings or to move. They are often not fed and do not get hydration. Many, according to this article, about 50%, die in transport or while waiting to be used for kapparot.
According to Ynet, Rabbi Aviner, the leading posek of Israeli National Religious Orthodoxy has ruled that
[I]t is preferable to use money for Kapparot and that the slaughter is not kosher due to the treatment of the chickens.
If this is an accurate report of Rabbi Aviner's ruling, this is quite significant. Copies of or links to the actual ruling would be much appreciated.
[Hat tip: SN.]