Why is the law of Ben Pekuah not utilised these days?
Is there any Halachic reason that it can not be introduced for commercial production on a large scale?
There is no halachic reason for which the laws of a ben pakua — a calf that is born alive after its mother has already been slaughtered — should not apply today.
Yet, I am not sure how much commencial use can be made of a ben pakua. It should be noted that although a ben pakua does not require shechitah according to Torah law (because it is considered already slaughtered), it nonetheless must be slaughtered by rabbinic decree if it is to be eaten. Thus we don’t save anything on slaughter costs.
A ben pakua can also cause trouble. If it fathers a calf, the new calf can never be slaughtered and thus never eaten (assuming the mother is a regular cow, and not a ben pakua). This is so because at birth this new calf is regarded as “half-slaughtered.” Thus, it cannot be slaughtered to be eaten, because the act of ritual slaughter is regarded as if it has taken too long (i.e., from when it was born — it is already half-slaughtered — until it is actually slaughtered). Ritual slaughter must be instantaneous.
The exception to this rule is if the original cow (the one that was slaughtered at the start of this episode) was itself a treifa, then its child will not be a ben pakua, thus allowing the new calf to be slaughtered and eaten.
This is a good question for a riddle: It is a case in which an animal being treifa causes another animal to be kosher — the “grandmother” cow’s being a treifa causes the “grandson” to be kosher (or, more exactly, prevents it from automatically being “half-slaughtered” and non-kosher.)
Sources: Shulchan Aruch, Yoreh Deah 13:4, Shach 12; the riddle was seen on the Or Sameach website.