Taken from:
http://www.foxvalleypets.org/cats/?details=28&page=678
Health Benefits
Spaying or neutering your pet eliminates or reduces a wide variety of health problems that can be very difficult and expensive to treat. Females no longer have to go through heat cycles and the health- and behavior-related problems that accompany them. Males are no longer controlled by their hormones, reducing aggressive behavior and the tendency to roam. But most importantly, spaying and neutering eliminates or reduces many types of cancer, tumors and other serious health complications. The simple fact is that altered pets generally live longer, healthier lives.
At the same time, pets that carry harmful genetic traits such as hip dysplasia or epilepsy should be neutered to prevent the spread or continuation of these conditions and others like them.
Fewer Injuries and Infections
Since sterilized animals no longer feel the need to roam to look for a mate, they have less chance of being involved in bloody fights that leave them with scars on their faces or missing parts of their ears and tails. They also avoid traumatic accidents such as being hit by a car. At the same time, the threat of abscesses caused by bites, infections and diseases transmitted by fighting and other contagious diseases are greatly reduced—allowing you to avoid expensive veterinary bills.
Fewer Diseases and Other Health Problems
After euthanasia, cancer is the number one killer of cats and dogs. It is very common for veterinarians to see unaltered pets for infections, conditions and diseases that are caused primarily by repeated surges of hormones.
MALES
Statistics prove that neutered males are healthier pets. Many diseases and health problems are caused by the effects of testosterone, a hormone produced in the testicles. By removing the source of testosterone, neutering reduces and eliminates the risks of many cancers and other hormone-related medical conditions. None of the behavioral or medical problems caused by testosterone are rare. Veterinarians deal with them on a daily basis.
Neutering eliminates the chances of developing:
• Testicular tumors and cancer. Testicular cancer is the second most frequently diagnosed cancer in older intact male dogs. There are several types of tumors, both benign and malignant, that can arise within the testicles.
Neutering greatly decreases the chances of developing:
• Prostatic disease. Over 80% of all unneutered male dogs develop prostate disease.
• Infections and disorders of the prostate glands. Prostate conditions such as prostate enlargement, cysts, and infection are all related to the presence of testosterone.
• Perianal tumors—These are tumors whose growth is stimulated by testosterone these are commonly observed in older, unaltered dogs. Perianal gland cancer is the third most frequently diagnosed cancer in older intact male dogs.
• Serious types of hernias. These are commonly observed in older, unaltered dogs and can occur on either or both sides of the anus. One of the long-term effects of testosterone causes the group of muscles near the anus to weaken or atrophy. The surgery to repair hernia complications can range from $300 to $1500, depending on the severity.
• nfections and disorders of the prepuce (the outer covering of the penis).
FEMALES
Spayed females are happier, healthier pets. The more heat cycles an unspayed pet goes through, the more susceptible she is to serious diseases. During an ovariohysterectomy (spaying), the uterus and ovaries are removed, ensuring that the hormones that cause health- and behavior-related problems are no longer produced. At the same time, many cancers, tumors and other medical conditions are reduced or eliminated.
Spaying eliminates the chances of developing:
• Pyometra. Pyometra is a serious and potentially fatal infection of the uterus experienced by many unspayed cats and dogs. If it is left untreated, your pet will most likely die.
• Ovarian cancer, cysts and infections. Ovarian cancer is a common occurrence in unaltered females.
• Uterine cancer and uterine infections. These are common occurrences in unaltered female dogs and cats, especially older pets.
• Acute metritis (infected uterus). This can be potentially fatal if not treated in time.
• Difficult pregnancy and delivery. This is common in older and ill cats.
• Pseudopregnancies. Some females go through a false pregnancy every time they come into heat.
Spaying greatly decreases the chances of developing:
• Breast cancer and tumors. The rate goes down to almost zero if the spay is done before the first heat cycle. Breast cancer is the most common malignant tumor in dogs, and the third most common cancer in cats. The chances of a female dog reaching 10 years of age without developing this potentially fatal tumor is less than 11% in some breeds with normal hormone production.
• Tumors of the reproductive system.
• Mammary cancer. Mammary cancer is very common in older unspayed females, and is the most common cancer to spread to the lungs.
• Mastitis (infection of the mammary glands). This can be potentially fatal if not treated in time.
• Mammary tumors. Unspayed females have about a 7 times greater chance of getting mammary tumors.
• False pregnancies.
• Certain skin conditions related to hormonal imbalances.
• Hair loss. The hair coat on many dogs suffers because of estrogen surges that occur with heat cycles or whelping. Their coats appear thin and the underlying skin is exposed in many areas. It can take 2 to 4 months for the hair to return to normal.