Complex sentence: In the 1930s the breeding of hybrid dogs became more common, especially among the German, Dutch and Belgian Shepherds, also partly due to the change in the Dutch Shepherd breed standard which, in 1914, eliminated all colors except brindle.
Split into simpler sentences: In the 1930s the breeding of hybrid dogs became more common, especially among the German, Dutch and Belgian Shepherds. Also, partly due to the change in the Dutch Shepherd breed standard which, in 1914, eliminated all colors except brindle.