The first, and often most easily understood, reason pet owners should have their cats and dogs gonadectomized is for the quality of their pets’ lives. I cite this as the reason most easily grasped by owners because of its relevance to their own lives. Other issues related to keeping pets intact are not as overt, such as the contribution to feral communities, or are misconceived as being controllable by other means, such as the belief that extra vigilance will keep their pet from escaping and roaming (I will explain these issues further in the other subheadings of this section). However, when veterinarians instruct people that their pets are at higher risk of developing certain health conditions if they are not sterilized, people listen more readily. Since this is the most empirical argument for the procedure and is supported by extensive research, it is also harder to combat with cultural disagreements.

Stress Reduction

One example of spaying/neutering providing better welfare is the reduction of stress related to unexpressed mating behavior. When a female cat or dog enters heat, copulation becomes the primary need of her and all surrounding male conspecifics during this time when  she is sexually receptive. This primal instinct  is driven by hormonal mechanisms that have evolved to ensure the animals are prioritizing reproduction during this short window (Reichler, 2009).

If a female goes through heat and is not allowed access to a male of her species to copulate during this time, it places a great deal of stress on both the female and the males in the area (Reichler, 2009). Research has shown that intact animals unable to reproduce during a female’s receptive period have dramatically increased plasma cortisol levels due to their inability to express this natural behavior.

Cat expressing typical estrus behavior, characterized by lowered copulatory position.
Photo source: https://i.ytimg.com/vi/o1Eczgku9ng/maxresdefault.jpg

Harm Reduction

While there is much debate over what time in an animal’s life is optimal to perform gonadectomy to maximize health, it is commonly understood that the procedure prevents the development of certain health risks overall (Reichler, 2009). There are a number of health benefits to gonad removal, particularly in females, with varying degrees of importance, so I will just mention a few here.

By excising the ovaries, the chance of all ovary-related health issues, like ovarian cysts or cancer, are completely eliminated. This makes sense intuitively, as the organs will no longer be present in the body, and thus cannot contribute to any maladies.

Gonadal steroid hormones produced by the ovaries are associated with the progression of a number of other conditions related to the reproductive tract, so the removal of these glands greatly reduces the chance of developing these conditions (Reichler, 2009). For example, intact female dogs have a 2-20% chance of growing malignant mammary tumors at some point in their lives, a process facilitated by gonadal steroids (Reichler, 2009). However, if a dog has her ovaries removed before she experiences her first estrus cycle, her chances of malignant mammary tumor growth decrease by 99.5% of that of intact females (Reichler, 2009).

Pets that are sterilized live 3-5 years longer than intact pets on average (Reichler, 2009). This may be due in part to the prevention of health risks associated with gonads.