Political parties are usually only concerned with human interests. The interests of animals hardly ever get a look in. This is why there is no or hardly any legislation with respect to animal rights in many countries. Animals are simply not a subject of political discussion. Politicians either express no opinion on the matter, and they are seldom confronted by journalists or fellow politicians with questions relating to animal welfare. The more voters show an interest in political standpoints about animal welfare, the more politicians will have to take a stand on it.
In this way, you can encourage politicians to speak out on animal welfare issues:
It is essential that politicians become aware of the fact that voters find animal welfare important. Indeed, no politician will openly admit to not being interested in animal welfare! Whether or not he will keep his promises is another matter, but it is important to make a start and to force politicians to formulate clear positions about animal welfare matters. You can do this by repeatedly asking them for their stance, and continuing to stimulate the social debate on animal welfare.