Complex sentence: The late 1970s were called the crisis of horse breeding in Europe, and within about twenty years, 80% of the Noriker horses disappeared, a fact that was directly connected to the third wave of mechanisation.
Split into simpler sentences: The late 1970s were called the crisis of horse breeding in Europe. In nearly twenty years 80% of the Noriker horses disappeared, a fact that was directly connected to the third wave of mechanisation.