I have read in the Rambam's Mishneh Torah regarding the slaughter of animals that the Shochet must inspect the knife before and after slaughtering each animal. I believe this is also the traditional Temani postion. Nowadays this practice is not followed; they inspect their blades then slaughter a number of animals after which they inspect the knife once again. This would seem to be a reliance on a bidi'eved postion that if the knife is still without a blemish all the animals which were slaughtered were kosher assuming no blemishes are found afterward. My source Rambam's MT Hilchot Shechitah 1:23-24. How do you view this position and what is the practical application in today's environment?
Hazal state explicitly that the knife must be checked before sh’hitta (TB Hulin 17b). Hazal do not state explicitly that the knife must be checked after sh’hitta. Whether this is required is a mahloqeth among the Rishonim z’l: Rashi, Rambam, Rashba hold that the knife must be checked after sh’hitta; Raavadh, Ba’al HaMaor and Raah hold that checking after sh’hitta is not necessary. According to the later view, checking after sh’hitta is a midath Hasiduth.
All agree that if the knife was checked and found to be kasher, all animals slaughtered with that knife are kasher (assuming no issue of T’rephoth is discovered later) unless the knife was found to be pasul after sh’hitta, in which case all animals slaughtered since the last check must be rejected. Checking after each and every animal is a form of insurance policy.
In modern abattoirs it is often not possible to check after each animal. Checking every 10 or 20 or more animals is acceptable, and confirms that all sh’hitta till that point was kasher.
Rabbi David Bar-Hayim