Complex sentence: During the 19th century, Shires were used extensively as cart horses to move goods from docks and factories and farms through the cities and countryside: the rough roads created a need for large horses with extensive musculature.
Split into simpler sentences: During the 19th century, Shires were used extensively as cart horses to move goods from the docks through the cities and countryside. The rough roads created a need for large horses with extensive musculature.