The Effects of Neutering
Bruce Fogle, D.V.M., M.R.C.V.S.
Ovariohysterectomies (or spays) and oophorectomies (or castrations) are the most common operations that veterinarians perform. Although owners like to feel they are having this surgery carried out to prevent unwanted pregnancies it is equally true that neutering operations are requested to alter the behavior of their cats. Owners simply don't want to put up with the fighting, roaming, spraying and unpleasant urine odor of intact toms, nor do they want to hear the plaintive cries or receive the pelvic presentations of females in heat. But how effective is neutering, and if it is to be carried out when is the best time for the surgery to be performed? And are there less dramatic alternatives?
Ben Hart at the University of California veterinary school at Davis was the first to investigate the value of neutering male cats. He interviewed cat owners twenty-three months after their cats had been castrated. The owners reported that in nine out of ten animals neutering reduced fighting, roaming and spraying. Sometimes the change took longer than in others, and by Hart's definition a 'rapid decline' meant within three weeks of neutering and a 'gradual decline' meant one that took up to four months. His findings were as follows:
Hart noted that it was not the most experienced fighters, roamers and
sprayers who continued their activity but rather the most vigorous ones, and he attributed
this variation to both inheritance and early learning. He also noted that a rapid decline
in one behavior did not necessarily correspond to decline in the other two behaviors. Some
cats would stop spraying and roaming but continued fighting. Others stopped fighting and
spraying but continued roaming. Finally, and importantly, he observed that there was no
relationship between the age at which a tomcat was neutered and the rate of decline in any
of these behaviors. The cats in this study were all between one and seven years old and
the effect of neutering was the same throughout the various ages.
The survey compared the behavior of intact males and females and yielded the following
results. Females are more playful, demand more attention, are more hygienic and are
friendlier to other household cats than are males. They are also slightly more
affectionate and excitable. Entire male cats are slightly more active and more destructive
than entire females and both are equally vocal and tolerate handling.
Finally, are there any safe alternatives to neutering that avoid surgery but prevent unwanted litters and social behaviors? The answer is a very qualified 'yes'. Both males and female cats can have their 'tubes' tied, surgery that does not interfere with hormone production but that simply prevents eggs or sperm from getting where they are most useful. Neither operation can be seriously recommended as routine because they don't resolve what is for many owners the major inconveniences of their cat's sexual behavior, urine smell, spraying, fighting and calling. Because all of these behaviors are hormonally influenced, other hormones given either in tablet form or by injection have been used for almost twenty years to counter sexual behavior. Estrous can be suppressed in cats by the administration of progesterone or a related progestogen, the hormones of pregnancy. Progestogens are also used to treat spraying and aggression in tomcats or neutered males and females, although their use is based on clinical experience rather than on controlled trials. The actual mechanism of action of progestogens still isn't known, but they can have a potent effect on modifying various feline behaviors and may act centrally on the brain. These hormones also have an anti-inflammatory effect, causing adrenal gland suppression, and this too might result in behavioral changes. The down side is that, although estrous can be suppressed by these hormones, there are possible side effects including weight gain, lethargy, loss of hair, womb infections, adrenal gland suppression, diabetes and mammary gland development. Some cats develop a pot-bellied appearance. Others suffer a heavy moult after the hormone treatment has been stopped. My clinical advice is that hormones are excellent for use in short-term therapy but have too many potential side effects to warrant their use as a replacement for spaying or castrating. Hormone treatment, and tubal ligation-vasectomy do not prevent mammary, ovarian, uterine, and testicle cancers. These cancers can only be prevented by neutering and spaying.
Additional Reading: Spaying & Neutering