Is it permissible, Islamically, to close the fallopian tubes of a cat that has given birth to four kittens, for fear that she will give birth again and again?

It is not permissible to castrate an animal or prevent its pregnancy except for a benefit or to avert harm, due to the Prophet's (peace and blessings be upon him) prohibition of castrating horses and beasts. However, if the castration is for a benefit, such as improving the meat of sheep, there is no religious impediment to it. The Prophet (peace and blessings be upon him) himself sacrificed two castrated rams.