Jon, the native grasses and legumes of Southern Africa cover a wide spectrum of climate adapted grasses, some farms have irrigated pastures such as kikuyu or stargrass which are often oversown to ryegrass for winter grazing. Lucene is popular as an irrigated crop for hay or limited grazing.
Many exotic cattle breeds (British and European) are kept in the cooler regeons, and often as crosses over native cattle for F1 and terminal crosses, all dairy breeds are exotics. I bred Tuli cattle while living in North Carolina due to my experience of their fertility and easy keeping in Rhodesia/Zimbabwe, I had self established Bermuda on my property there, the field was an old cotton field when I bought it with mixed, rough herbage, the rotational grazing resulted in the improvement in grass type and bio mass.
Luis, are you breeding the South Devon or the "Red" North Devon? I had some experience managing North Devons for a while, and have used the bulls in a grass finishing program.