Complex sentence: They were once kept in large herds by professional herdsmen called "Junglies", but with the introduction of irrigation they began to be kept in smaller numbers by the farmers of the region, who used them as draft and dairy animals.
Split into simpler sentences: They were once kept in large herds by professional herdsmen called "Junglies". However, with the introduction of irrigation to the region they began to be kept in smaller numbers by the farmers of the region, who used them as draft and dairy animals.