It's not really an idiom as such, but most people would know what it means. The 'trough' is a feeding trough - where pigs eat. In western culture, a pig is not considered a polite eater! So - the idea is (i) that you don't want to miss out on the food, and to a lesser degree (ii) that you are part of a relatively uncivilised group of animals trying to get as much food as possible.

People would guess what it meant, but it is not really an idiom. It might be more common to say lose your place at the table, but even that isn't a very common idiom.