Introduction When confronted with a case of feline infertility, male or fe- male, a complete history including vaccination and disease status is essential. Many issues can be contributed to improp- er management (see next section on history). A good general physical examination (observing for comorbidities that could affect reproduction) is performed next. Body condition of the cat, overall appearance, grooming, and attitude should be ob- served in both males and females. In the male, special atten- tion should be placed on examining the mouth and gums. Mouth pain (e.g., gingivitis or tooth pain) can affect the abil- ity of the male to bite the scruff of the female when mating and therefore hinder the breeding attempt. Any back or rear limb pain in the male can also affect the breeding process or his willingness to mate. An external reproductive examina- tion should follow the general physical examination and will be discussed later for the female and male separately. Blood analyses (e.g., complete blood count, serum chemistry, and possibly hormonal testing) may be indicated depending on the findings of the physical and reproductive examinations. Ultrasonography should be performed to evaluate both testes in the male, and uterus and ovaries in the female. Sedation may be required depending on the cooperative behavior of the patient. If external or internal reproductive abnormalities are present, or if there is no other obvious cause for the infer- tility, a karyotype of one or both members of the breeding pair may be necessary to confirm whether the genetic makeup of the animal is normal. History Specific questions to gain a baseline knowledge of the cattery management include.1 Clinical approach to infertility in the cat Aime Johnson Auburn University College of Veterinary Medicine Auburn, AL Abstract Causes of infertility in the cat are often multifactorial. Cattery management should be addressed prior to evaluation of individual animals. Factors such as housing/lighting, preventive care, and disease status of the colony should be evaluated. A complete phys- ical examination is vital to rule in or out anatomical abnormalities leading to infertility. In the tom and queen, good breeding management is vital for success. In queens, infertility can be caused by persistent receptivity/estrous behavior, refusal of the male, and ovulation without pregnancy. When evaluating a tom, failure to mate or failure to achieve pregnancies are the most common categories. A detailed history and complete breeding soundness examination is important to differentiate and identify potential causes of infertility. Keywords: Cat, infertility, queen, tom • How many animals are housed in the facility (male and fe- male, breeding and nonbreeding)? • What are their ages? • What is the source of each animal and how long has each been with the colony? • What is the diet, water source, and preventative health pol- icy? • What is the supplemental lighting program? • What is the current disinfection policy for floors, litterbox- es, bowls, etc.? • What is the procedure for bringing male and female togeth- er? • What is the procedure for pregnancy confirmation? • Where are pregnant queens housed during pregnancy, de- livery, and lactation? • What bedding or boxes are provided to the animals at each stage (breeding, pregnancy, queening, and lactation)? • Is breeding or queening observed, or does it occur with no one present? • How are kittens managed from birth to weaning? • Can a detailed breeding and queening report for each ani- mal be provided? • What are the specific issues the cattery is experiencing? Additional questions may be necessary depending on the an- swers received. Cattery Management Vaccination status of all animals in the colony or household should be evaluated to ensure adequate disease control. Al- though a closed colony is preferable with no new animals en- tering, such a policy may also limit the introduction of new genetics. A quarantine period with adequate testing proce- dures should be mandatory for all new additions. A quaran- tine process should also be in place for any cats that leave and return to the colony for breeding, exhibition, etc. Cats in dif- ferent stages should be housed separately. Breeding animals, pregnant, and nursing mothers should be kept away from all other cats. Late pregnant and lactating mothers should be kept in a quiet comfortable space to reduce stress and minimize stress-induced cannibalization of their young. In catteries, strict sanitation and adequate ventilation are es- sential to reduce or eliminate disease. Poor sanitation often leads to clinical signs of disease and neonatal mortality from sepsis. Standard operating procedures should be followed to prevent hygiene errors. Litter boxes, bedding, toys, food, and water bowls should be cleaned and disinfected regularly. Frequency will depend on the density of the cattery, but in general, cleaning should be performed daily with complete disinfectant done at least weekly. Caution is needed to ensure that the disinfectant used is at an appropriate concentration, is sufficient for the major pathogens, and is safe for cats. Read- ers are encouraged to consult guidelines2 for appropriate dis- infectants for a variety of pathogens. Lighting The queen is a long day breeder and cycles when the day length increases (February - October in the Northern Hemisphere). During shorter days of the year, cyclicity ceases and queens enter an anestrous stage. Toms have an overall decrease in hor- mone production and sperm quality during the nonbreeding season; however, it is not substantial enough to affect fertility.3 When exposed to artificial lighting for 12 - 14 hours per day, cats will continue to maintain cyclicity. Most catteries use a 14:10 hours light:dark schedule. It is noteworthy that in this author’s experience, even cats maintained under this lighting system may experience a slight decrease in pregnancy rates during the shorter days of the year. A queen will typically start cyclicity within 1 - 2 months after initiating an artificial light- ing period. If cats are exposed to light 24 hours a day, cyclicity will be maintained; however, the number of ‘heat cycles’ was reduced from 2 per month to only 1.4 If a group of breed- ing animals has been maintained under long-term artificial lighting (years) and the overall fertility has declined, allowing the queen to experience a season of anestrus by shortening the lighting period (8 hours of light) for 2 - 3 months may be beneficial before restarting the extended day lighting. Cats housed in a home setting are often exposed to a combination of natural and artificial light. However, animals have the free- dom to hide under objects or in dark rooms so the light they are exposed to is variable. Because of this, queens in a house setting will often display seasonality and not exhibit cyclicity during the short daylight period. Queen Causes of infertility in the queen are often classified into broad categories and this discussion will focus on those causes that fail to produce a pregnancy despite appropriate breeding management. This discussion will not cover early pregnancy loss that may appear as infertility and must be differentiat- ed from true infertility. Persistent receptivity/estrous behav- ior, refusal of the male, and ovulation without pregnancy are 3 main categories to explore. A good history can determine which category applies to the patient. Persistent estrus/receptivity Persistent estrus and/or receptivity can be identified when a queen either continually displays behavioral signs of estrus, vaginal cytology is > 70% cornified, or she accepts the male continuously. Persistent estrus may appear to occur in queens that naturally display a shorter interestrus period (Siamese) and owners reporting that she is ‘in heat all the time’. Daily records of behavior by the owner and a vaginal cytology every 2 - 3 days would determine if the queen is exhibiting normal cyclicity. In a natural breeding situation where the queen is presented to the male, queens that exhibit persistent recep- tivity are likely failing to ovulate. Failure to ovulate can be suspected based on a history of a female exposed to the male, may or may not have been mated, refuse the male only to be- gin estrous behavior again 8 - 10 days later. In short, the queen is having normal cyclicity. Ovulation failure may result from lack of adequate stimulation to produce LH surge or a primary ovarian dysfunction (e.g., ovarian follicular cysts). Evaluation of the breeding records, number of witnessed matings, and presence or absence of the ‘after reaction’ of the queen fol- lowing coitus will assist in assessing if adequate stimulation has occurred. The ‘after reaction’ follows intromission and is identified when the female rolls on her back, rubs her face on objects, and licks her perineum. This reaction lasts several minutes while the male usually watches from a distance. A survey of purebred catteries in Sweden determined that only 35% of matings occurred when owners were present.5 Wireless cameras are a helpful tool to evaluate matings that occurred unobserved. Number and timing of matings that occur when queen is placed with the male will affect ovulation success. Only 1 of 12 cats ovulated with a single mating on day 1 of estrus, whereas 4 of 12 ovulated after a single mating on day 4 of estrus.6 When 3 matings on a single day were allowed, 10 of 12 cats ovulated on days 1, 2, and 3 of the estrus period.6 It is generally recommended that 4 or more matings are needed to provide sufficient stimulation and LH release for ovulation to occur. Confirmation of ovulation can be made by evaluating serum progesterone concentrations one week after observed matings. If progesterone concentrations are 2 ng/ml, luteal tissue is present. With pairs that are not compatible, artificial insemination should be performed. Ovulation induction should be fol- lowed by semen collection and insemination 24 - 30 hours later. If spontaneous ovulation has occurred, the nonpregnant luteal phase lasts 35-40 days. Queens should be monitored every 1 - 2 weeks utilizing vaginal cytology, behavior, or pro- gesterone assay to determine when the luteal phase has end- ed. Reintroduction to the male can occur after this period. Ovulation without pregnancy Queens that are mated successfully but fail to become preg- nant will undergo a ‘pseudopregnancy’ stage. This is defined as a shortened luteal phase lasting 35 - 40 days instead of the full length of pregnancy. Following mating, ovulation should be confirmed by testing the queen’s serum progesterone (> 2 ng/ml) concentrations. Pregnancy diagnosis can be performed via ultrasonography ~ 30 days after mating. Successful mating without pregnancy can be due to either the male or female. A full breeding soundness examination with semen analysis should be performed on the male. Causes in the female are usually due to uterine pathology. A common primary uterine problem observed in the queen is cystic endometrial hyperplasia (CEH) with or without con- current pyometra. In the author’s research cattery, ~ 75% of queens diagnosed with infertility (failure to produce offspring following appropriately managed breeding[s]) had histologi- cal evidence of CEH within their uterus. Clinical signs in this CEH affected group of queens were first noted at 3 - 4 years of age (decreased litter size or failure to produce kittens consis- tently). Intact female cats over 5 years of age have a greater risk of developing clinical disease associated with CEH/pyome- tra.11 An 88% incidence of CEH was observed in cats > 5 years old compared to 30% in cats aged 2 - 4, with a much greater incidence of the disease in colony raised cats compared to fe- ral cats.12 Diagnosis is suspected based on history of reduced fertility. A thickened uterine wall with prominent endometrial folds and small cystic areas within the uterus may be observed on ultrasound. A uterine biopsy provides definitive diagnosis and may be required for less severe cases. Currently, uterine biopsy is best obtained surgically. If CEH is severe, prognosis for fertility is guarded and ovariohysterectomy is recommend- ed. Pyometra often occurs secondary to CEH and may result in ovariohysterectomy (preferred treatment for older queens not needed for future breeding). However, unlike observed in the bitch, queens are often not systemically ill and the only clin- ical sign may be a purulent vaginal discharge. Treatment with a fluroquinolone, native prostaglandin, and cabergoline can provide appropriate successful medical treatment. Medical management of pyometra in the queen should be performed on a case-by-case basis. Underlying CEH cannot be corrected. Subclinical endometritis may also cause infertility in the cat. It has become a leading cause of infertility in the bitch. Among biopsy samples from 399 intact bitches, the most common lesion observed was endometritis (42.6%).13 Although there is less information describing this lesion in the queen, it is likely that this pathology is also a substantial cause of infertility in this species. Miscellaneous causes There are countless other potential causes of infertility or early pregnancy loss in the queen. Infectious (bacterial and viral) should be ruled out with serology and culture. Vaginal cul- ture may be obtained but should be interpreted with caution due to high likelihood of contamination when swabbing the caudal vaginal canal. A cranial vaginal sample would be ideal; however, when in estrus, the queen’s cranial vagina measures only 1 - 2 mm in diameter when compared to 4 mm of the caudal vagina, making sampling difficult.14 If a pure culture is obtained, treatment would be indicated based on the suscep- tibility pattern. Pure or heavy growth of ß-hemolytic streptococci or Escherichia coli has been associated with endometritis and pyometra. Mycoplasma sp., Ureaplasma sp., Coxiella burnetti, and Chlamydia sp. have all been implicated in infertility. A PCR test is the most sensitive assay for these bacteria and diagnosis should be based on results and clinical signs. Treatment with antibiotics should be reserved for animals exhibiting clinical signs and based on susceptibility of the positive culture. Tom When evaluating infertility in a pair, the tom is the easier to evaluate. A complete breeding soundness examination should be performed starting with history, general physical examina- tion, and external reproductive examination. Puberty occurs between 7 - 12 months. Prior to puberty, adhesion of the bal- anopreputial fold prevents full exposure of the penis. Break- down is androgen dependent and therefore makes this an initial reference point for pre versus post pubertal animals.15 Androgen dependent penile spines are present on the proxi- mal ⅔ of penis indicating the presence of circulating testos- terone. Testes should be located within the scrotum and be freely movable. Scrotal skin should be free from dermatitis or wounds. Both testes should palpate slightly firm and of sim- ilar size. Ultrasonography of the testes should be performed after palpation. Testes should be round to slightly oval. Lit- erature relating size of the testes to fertility is lacking in the tom but can be inferred based on other species. Average daily sperm output for a standard tom has been estimated at 32 x 106.16 Via ultrasonography, length, width, and height of each testis should be measured and the testicular volume (TV) cal- culated using the formula for an ellipse simplified to TV = 0.2533 x Length x Width x Height). The process for placement of the ultrasound probe for measuring has been described.17 These measurements are most helpful when evaluating testic- ular size in a single tom over time rather than a comparison among males. Semen collection in the tom is more difficult than other do- mestic species. Collection using a home-made artificial vagina was first reported in the 1970s.18 In a clinic setting, collection using an artificial vagina is not practical unless the tom has been previously trained. The most effective method of semen collection is electroejaculation. The process this author uses has been described.19 Although electroejaculation is the most consistent in obtaining sperm from the tom, it requires spe- cialized equipment that may not be available in all clinics. The most practical method of obtaining a semen sample in the clinic setting is urethral catheterization after pharmaco- logical induction. This technique was described using a high dose of medetomidine (120 μg/kg).20 Since medetomidine is no longer available in the US, dexmedetomidine can be used at a comparable dose (60 μg/kg). Lower doses of both medi- cations were studied (50 μg/kg medetomidine and 25 μg/kg dexmedetomidine) but the sedation level and ejaculate col- lection were inadequate.21 Once full sedation is achieved (cat in lateral and unresponsive), an open ended tomcat catheter should be inserted into the urethra 8 - 9 cm. Measuring and marking the catheter prior to insertion will assist with proper placement. Care must be taken not to enter the bladder. A single catheterization inserted and immediately removed fol- lowing full sedation was preferrable to multiple catheteriza- tion attempts and provided an adequate sperm sample with- out damaging the urethra.22 The sample can be flushed from the catheter using an appropriate extender. This author prefers making extender using Ham’s F-10 with 25 mM Hepes, 1mM pyruvate and glutamine, and 5% fetal bovine serum. An alter- native that is commercially available is TEST yolk buffer (re- frigeration media, Irving Scientific). However, analysis of the motion characteristics may be difficult due to the interface egg yolk droplets if the extender is not filtered prior to use. Once the sample is obtained, a complete sperm analysis should be performed including motility, morphology, and cytology to evaluate for inflammatory cells. Causes of infertility in the male can be classified into unable/ refusal to mate and mating but not achieving pregnancies. If the male displays reduced libido, it could be due to stress, an overly aggressive female, or systemic disease. Apart from his- tory and physical examination, routine blood work should be performed. Female should be removed from the male to allow the male to rest. A second female or the same female after confirming that she is in estrus can be returned several days later. If male is refusing to breed a female, physical limitations should be addressed (e.g. sore back or mouth). Primary pe- nile problems (e.g. persistent frenulum, hair ring, priapism, or paraphimosis) should also be evaluated. Observation of the interaction between the male and female is ideal to assess behavioral problems with the male alone, or the pair. Failure to produce litters For toms that are breeding naturally, inducing ovulation, but not achieving pregnancies, a semen analysis is vital. Terato- spermia, defined as > 40% abnormal sperm, is observed in small populations of cats where inbreeding or excessive line breeding has occurred.23 A single generation of inbreeding (offspring bred to parent) produced male offspring with < 15% morphologically normal sperm compared to 55% mor- phologically normal sperm in control animals, indicating that loss of genetic diversity leads to increased teratospermia in as short as 1 generation.23 Unlike in other species, many terato- spermic ejaculates in the tom demonstrate adequate motility (> 70%), in spite of low numbers of morphologically normal sperm. Because the tom breeds multiple times a day, even toms that are classified as teratospermic may have normal fer- tility. Azoospermia is the complete absence of sperm in the ejac- ulate. To differentiate this from ejaculation failure, seminal plasma alkaline phosphatase concentrations can be deter- mined. A higher alkaline phosphatase (typically > 5,000 IU/l) concentration confirms that the sample has originated from the epididymis and a complete ejaculate was obtained. If azo- ospermia is confirmed, prognosis for return to fertility is poor unless a treatable underlaying disease is diagnosed. The tom should have a second semen evaluation 2 - 3 months later to detect improvement. Culture of the ejaculate may be indicated if inflammatory cells are identified in the ejaculate. A pure culture should be a cause for concern and should be treated based on susceptibility. Conclusion Infertility in the queen and tom can be multifactorial. History and examination can help to prepare a differential list that leads to diagnosis of the specific problem. Treatment varies and should be directed at the specific cause, if identified. Conflict of interest None to declare. References 1. Johnson AK: Normal feline reproduction: The queen. J Feline Med Surg 2022;24:204-211. 2. 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