Firstly, neutering your female dog greatly reduces her chance of developing mammary gland tumours and uterine diseases such as pyometra and uterine cancers. In your male dog, castration prevents prostate diseases. In both your male and female pet, these diseases can be fatal. You also prevent sexually transmittable diseases such as venereal tumours.
Secondly, castrating your male dogs and cats before they are sexually mature almost always ensures that they do not develop the habit of marking their territories (urinating). Marking of territories is a very unpleasant experience for many owners.
Thirdly, there are too many homeless animals in Malaysia. Every day, these stray animals suffer and die from accidents, starvation, disease conditions and being inhumanely caught and killed by dog and cat catchers, employed by the local town councils. As a responsible pet owner and animal lover you can help contribute in reducing the stray population and their suffering by neutering your pets.