Wanting the Beast to Look Fat
A beast might be Assur BeHanaAh, banned from all benefit, if it has been worshipped or prepared for idolatry, or if it has attacked people and must be killed.
In these cases, is the entire beast banned or only some parts?
Sometimes the stomach contents are prohibited but not always.
The Gemara AZ 34b, explains that the Peresh, the contents of the stomach, are prohibited in one case but not the other. The Peresh of the beast dedicated for idolatry is banned; the Peresh of the beast killed by BD, is permitted.
The Gemara explains that unlike the beast killed by BD where the fatness of the beast is irrelevant, the beast offered for idolatry is certainly preferred fat. The fatter the beast the greater is the honour to the idol and the more pleased is the one who offers this beast; therefore even the Peresh is prohibited.
Firstly, I would never have imagined that a well fed beast that has not eaten in the past few days or so would look any fatter had it been eating and not fasting.
Secondly, the starting point assumes, and the conclusion supports, that Peresh is not in normal circumstances, to be included as part of the beast. Why is this so? Furthermore, it would appear that the waste in the digestive tract, urine and whatever other parts may be considered to be “waste” or “non-essential parts” are not prohibited even of a beast offered for idolatry. They are not an essential or proper part of the beast and their presence does not enhance its value as an idolatrous sacrifice.