Thanks for the correction, there was a big exhibit next to this one with numerous Bantengs of all ages but only cows and calves but this one, next door, had two huge bulls and I assumed them to be the breeding bulls.
Chlidonias: this is not the same enclosure. There were Gaur in two different enclosures. The above one was for Malayan Gaur while the other one (where your photo was taken) was for Indian Gaur some good distance away, I remember it being close to the bears. The exhibit for Indian Gaur was not as big as this one and rather bare, it held a good number of animals while there were only these two bulls in the above one.
OK. My recollections of Zoo Negara are a bit hazy. I have an overall remembrance that the zoo on the whole was pretty decent except for the bears (terrible) and monkeys (big tall cages but very bare). The hoofstock in particular mostly did very well as far as enclosures went. I only ended up taking a handful of photos though, for some reason I cannot remember...