Maybe. There is a growing body of evidence that refutes the commonly held notion that neutering prepubescent animals is harmless. We now know that neutered animals have reduced metabolic rates, delayed growth plate closure, and their bodies select fat over muscle mass when compared to intact (non-neutered) animals. We know that estrogen responsive urinary incontinence in female dogs is a direct result of neutering. We also know that femoral head growth plate fractures are sometimes found in young neutered male cats. There are two studies that identify neutering prior to maturity as a risk factor for cruciate ligament rupture. Another study identified neutered animals as being at increased risk of developing bone tumours. And yet another study identified a correlation between neutering early in life and a shortened life span in female Rottweilers. Though sterilization is by no means a license for obesity, the slowed rate of metabolism and selection of fat over muscle mass in neutered animals almost certainly contributes to the incidence of obesity in Canada’s pets.

The two traditional reasons we neuter our pets are for population control and the prevention of undesirable sexual behaviours. A neutered pet cannot reproduce, period. Whether neutering males reduces generalized aggression is not proven, though it certainly will prevent males from fighting over a female in heat. Some will insist that there are “health benefits” to neutering such as cancer prevention. This is only partly true. Neutered females do have significantly reduced rates of mammary cancer and do not get ovarian or uterine cancer. However, the landmark 1968 study that highlights this so called “health benefit” also showed that the rates for all other forms of cancer go up such that there is no change in the overall incidence of cancer between neutered and intact female dogs.

Obviously, neutered males do not develop testicular cancer, though the majority of these tumours are benign.

Unfortunately, no equivalent study for males like the 1968 study of female dogs exists, though we do know that there is no measurable difference in prostatic cancer between intact and neutered male dogs. Other purported “health benefits” include the prevention of Pyometra (a life threatening infection of the uterus), which is true; however the risk of Pyometra is virtually zero until after the second heat cycle.