Complex sentence: Danzig and his son, Danehill, were dominant bay sires along with another 17 of Danzig's sons: they would not produce chestnut progeny and only a grey if the foal's dam was grey.
Split into simpler sentences: Danzig and his son, Danehill, were dominant bay sires along with another 17 of Danzig's sons. This meant that they would not produce chestnut progeny and only a grey if the foal's dam was grey.