Proper ovulation in females and ejaculation of fertile and normal sperm by males are regulated through a sequence of events in the brain, nervous system, and sexual organs. For optimal results, ovulation and deposition of semen into the female genital tract must be closely synchronized. Failure of any step in either sex leads to infertility or sterility. The ultimate result of infertility is the failure to produce offspring. In females, infertility may be due to the absence of the estrous cycle, abnormal ovulation, failure to conceive, or prenatal death. Major infertility problems in males are caused by disturbances in the production, transport, or storage of sperm; loss of libido; and partial or complete inability to mate or to stimulate ovulation in the female. Most major infertility problems are complex; several factors, singly or in combination, can cause failure to produce offspring.
Infectious diseases are a less likely cause of infertility. In cats, toxoplasmosis Toxoplasmosis in Cats Toxoplasmosis is caused by Toxoplasma gondii, a protozoan parasite that infects humans and other warm-blooded animals. It has been found worldwide. Wild and domestic felines (members... read more , feline leukemia virus infection, feline infectious peritonitis Feline Infectious Peritonitis (FIP) Feline infectious peritonitis (often called FIP) is a severe, usually fatal disease caused by a feline coronavirus. Coronaviruses are a family of viruses that chiefly cause respiratory infections... read more , and feline viral rhinotracheitis Feline Respiratory Disease Complex (Feline Viral Rhinotracheitis, Feline Calicivirus) Feline respiratory disease complex is a set of respiratory illnesses caused by a group of organisms that can cause infection alone or together. It includes those illnesses with signs including... read more may cause infertility or the death of the fetus or newborn. Because the feline estrus cycle is controlled by light, cats should be exposed to appropriate amounts of light before breeding. Anatomic problems (such as scarring within the Fallopian tubes), metabolic disorders (such as severe illness), excessive heat or body temperature, functional disorders (such as cancer, inflammation, or cysts), and some drugs can also cause infertility. Interestingly, tortoise-shell and calico male cats are sterile (unable to sire kittens) due to a genetic abnormality.
Your veterinarian will establish whether it is the female or male that is infertile based on the history, physical examination, and diagnostic tests, such as semen evaluation, ultrasonography, or laboratory tests. In some cases both animals may contribute to infertility. Infertility is seldom accompanied by obvious signs of illness or infection. Lower fertility may be hereditary, and your veterinarian will consider this issue when dealing with fertility problems.
Infertility can be treated by administration of hormones that act directly on the ovaries or regulate their functions, or act to help maintain pregnancy. Hormonal treatment can also work on male cats with low sperm counts or poor libido. On the other hand, hormonal treatment can also be used to prevent pregnancy after an undesired mating.
Antibiotics are used for treatment of infection of the reproductive tracts. The selection of the antibiotic is based on tests that determine the nature of the bacteria or infectious agent.
In some circumstances, unsatisfactory results with antibiotics and increased concerns about bacteria that develop resistance to a particular antibiotic have led veterinarians to use treatments other than antibiotics for infections of the reproductive tract. These drugs boost local immune defenses and can be used alone or in combination with antibiotics.
Also see professional content regarding infertility in small animals Infertility in Dogs and Cats The most common cause of infertility in dogs and cats is related to husbandry problems (timing, techniques, male selection). Breeding with a proven fertile male must occur at the optimal time... read more 
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