Complex sentence: As railroads became the primary method for moving stock to market, the demand for the Rottweiller breed declined, as did their numbers, so severely diminished by 1882 that a show in Heilbronn, featured only one very poor representative of the breed.
Split into simpler sentences: As railroads became the primary method for moving stock to market, the need for the breed declined, as did the number of Rottweilers. The number of Rottweilers diminished so severely that by 1882 in a dog show in Heilbronn, there was only one very poor representative of the breed.