Avodah Zarah 14: White Roosters

Another mishnah placed on the previous daf: Commercial prohibitions when attempting business with idolaters - but specifically all year long, and not just at the time of their festivals. Among the prohibited items to sell to these non-Jews is a white rooster - though if sold among other roosters, and with a clipped toe (so not perfect for sacrifice), then they may be sold. Plus, the question of selling a damaged white rooster to one who asks for it. Does that mean the non-Jews don't want to make this offering, or are they putting one over on the seller? Also, a much longer, more detailed tractate of Avodah Zarah in Abraham's time (Note: of the 400 chapters mentioned - "400" is generally understood in the Gemara as being the language of exaggeration).