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Major Manifestations of Infertility in the Female Camelidae
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Foreword
The reproductive rate in camelidae has always been described as low. Many theories have been advanced to explain this low rate of reproduction based on physiological characteristics of these species. However, no complete study has been conducted to thoroughly investigate the part that infertility (congenital and acquired) plays in the reduction of reproductive performance in general. This lack of knowledge on pathological processes in the camelidae is slowly being reduced because of the increase in individual care, especially for valuable animals. Our data suggests that acquired infertility in the female camelidae in general, and in the dromedary in particular, plays a more important role in overall low reproductive rate than previously thought. In our clinic, the incidence of reproductive failure due to a pathological process in the genital tract ranges between 15 and 35%, depending on herds.
In alpacas, the mean annual fertility reported is 50%,(54, 55) while in llamas the mean birth rate is 45.9%.(36) Low fertility in alpacas seems to be due to the reported 50 and 57.8% embryo mortality up to 30 days of gestation.(31, 55)
Diagnosis and treatment of reproductive diseases is rapidly becoming a major part of the veterinary care provided to the camelidae industry, especially when dealing with genetically superior animals.
Reproductive diseases and infertility in the female can be placed into one of 4 categories of complaints which are in order of frequency: 1) failure of the female to become pregnant after several matings or inseminations (Repeat Breeding Syndrome), 2) failure to maintain pregnancy after breeding and conception (early embryonic death, fetal loss, or abortion), 3) Failure to complete breeding because of physical or behavioral problems (intromission difficulties, refusal of the male), 4) observed abnormalities in the genitalia (e.g. abnormal conformation or lesions of the vulva and perineum, abnormal vaginal discharge).
Repeat Breeding Syndrome
The Repeat Breeding Syndrome is very difficult to define in camelidae because of the peculiar "cycle" and the induced nature of ovulation in these species. We recommend that all animals that fail to become pregnant after two breedings should fall into this category. Etiologically the Repeat Breeding Syndrome is due to two main reasons: failure to conceive and early embryo loss.
Incidence
There is little data concerning the incidence of Repeat Breeding Syndrome in camelidae. In dromedary herds under our supervision, the parturition rate varies between 62 and 85% with very little observed abortion. Therefore, it can be assumed that at least for the dromedary female, the incidence of repeat breeding can be as high as 40% in herds with reproductive problems.
Probable causes
Repeat Breeding Syndrome can be due to many factors, some of which are pathological while others are management errors. The pathological factors involved in repeat breeding include all conditions that may affect gametes or early embryo survival. Management factors are certainly a major cause of infertility in camelidae. In one study, 76% of the dromedary females culled for infertility due to repeat breeding did not show any lesions on their reproductive tract.(10) Management of reproduction in camelidae is very complicated because the signs of estrus are not very reliable and the timing of breeding in relationship to growth and size of the follicle are very critical for induction of ovulation.
The challenge that the practitioner faces in cases of repeat breeding are great and a diagnosis can only be achieved with a complete and sound approach to the problem. Table 1 shows the different possibilities and methodology of approach for the determination of the etiology of repeat breeding.
Fertilization failure
Our studies on embryo collection in donors bred without any hormonal treatment indicate that under normal conditions (normal female bred to a reproductively sound male) fertilization rates are in the range of 80 to 85%. This rate is probably lower than in reality because it does not take into account losses that occur before the passage of the embryo into the uterus. Failure of fertilization can be due to either an ovulation failure, lack of fertile semen at the time of ovum descent, or disturbance of the oviductal transport of semen and the ovum.
Ovulation failure
Failure of ovulation even after adequate mating is a very common problem in camelidae. In our embryo transfer program, the ovulation rate detected by ultrasonography and progesterone assay at the time of flushing is 87% although breeding is completely controlled and the female is bred only if she has a mature follicle and displays increased uterine tone. Similar ovulation rates have been reported in the llama, alpaca, and the dromedary by other authors.(6, 14, 15, 24-27, 29, 56, 107, 114, 117) When the same criteria of selection for breeding (mature follicle and increased contraction of the uterus) are used for hormonal induction of ovulation with hCG, the ovulation rate obtained is higher and in some cases reaches 100%.(15, 106, 114) This observation suggests that ovulation failure is due to inadequate LH release after copulation.(15, 25, 29, 106, 107) This lack of, or insufficient, LH release could be due to a hypthalamo-pituitary function disturbance or to a reduced stimulatory effect of copulation. It has been shown in the Bactrian camel that some males have a low fertility because they fail to induce ovulation.(130-132) It was suggested that in the case of these males, there is a reduced potency or concentration of a GnRH-like factor present in semen that causes ovulation.(87, 131)
Failure of ovulation is also observed when the female is bred after the follicle has started its regression. There are no studies concerning the effect of other external factors such as handling, lactation, and nutrition on the incidence of ovulation failure in the dromedary. In the alpaca and llama, early rebreeding after parturition (< 20 days) is usually accompanied by a lower ovulation rate.(28)
Determination of the occurrence of ovulation should be an integral part of the reproductive management of the female camelidae. Control of ovulation can be done by ultrasonography or by progesterone assays. New tests are being developed to allow detection of LH peak after breeding. In intensively managed animals, bred females may benefit from an hCG injection just after breeding. This is particularly helpful in females known to have inadequate LH surge after mating or in superovulated females.
Category of causes | Probable causes | Likely direct cause |
---|---|---|
Management | lack of expertise in breeding camelidae, breeding in absence of mature follicle, incomplete breeding | |
Failure of ovulation | Incomplete breeding, lack of LH release, ovarian pathology, bad timing of mating | |
Fertilization failure | Failure of ejaculation | male infertility, age of the male, male overuse |
Oviductal transport problem | uterine tube pathology, ovarian bursa pathology | |
Poor survival of semen | uterine pathology, male infertility, semen quality (artificial insemination) | |
Abnormal uterine environment | uterine infections, uterine fibrosis | |
Early embryo loss | Hormonal factors | abnormal corpus luteum |
External factors | management, nutrition. |
Failure of ova transport
Fertilization takes place in the lower third section of the uterine tube. In order for this phenomenon to occur, the ovum should be collected by the fimbria of the ovarian bursa and transported down to the fertilization site to meet the spermatozoa. Ova transport can be impaired by several pathological processes in the bursa (i.e. bursitis) and uterine tube (i.e. salpingitis; occlusions...). These pathologies are discussed in more detail in a special section of the present chapter (cf. Pathology of the bursa and uterine tube).
Impaired semen viability and transport
In camelidae, semen is deposited partially in utero at breeding. It then migrates to the utero-tubal region which acts as a sperm reservoir. Survival of spermatozoa in the genital tract of the female depends on the initial quality of semen and on the uterine environment in which they swim. Survival of spermatozoa is reduced in the case of uterine infection. Also, a lower survival of semen is to be expected if it has been subjected to treatments such as freezing and thawing. There are no experimental studies on the life span of the gametes in camelidae. Life span of the gametes should not be a major cause of fertilization failure in the camelidae because ovulation occurs within a relatively fixed time after mating and ejaculation. However, the life span of the gametes can become an important factor in fertilization failure if artificial insemination is used and ovulation is induced.
Inability to complete mating
Inability to complete copulation is a frequent cause of fertilization failure. This is due to either lack of intromission or partial intromission without ejaculation. Difficulties in intromission are encountered in the presence of vaginal or vestibular anomalies (i.e. partial or total adhesions or persistent non-perforated hymen) or discrepancies in size between the male and female. These problems are easily identified by an experienced breeder. However, we have had several cases referred to us for repeat breeding in which there was complete occlusion of the vagina or the cervix (cf. Pathology of the cervix and vagina).
Early embryonic death
Early embryonic death is probably the most common form of reduced fertility in the llama and alpaca. Incidence of early embryonic death in these species can be as high as 57.8%.(11, 31, 36, 37, 53, 55, 110-113, 116) In the dromedary, early embryonic death is suspected as a cause of reproductive wastage.(1, 2, 7, 8, 83, 84, 100-102) However its incidence, based on abattoir studies, is very low (0.12% to 0.99%).(95, 99, 103) Our clinical data on 689 females shows that the incidence of embryo loss approaches 32%. Most of the pregnancy wastage due to early embryonic loss occurs before day 45 and therefore goes unnoticed in the llama and alpaca. In the dromedary, all the breeders are familiar with the characteristic behavior of the female during pregnancy (tail curling, opisthotonos) and embryonic loss is suspected when the female fails to show these signs after she has been diagnosed pregnant.
The reason for such a high incidence of embryonic mortality in camelidae is not clear. Earlier reports have suggested that the side of ovulation may have an effect since all pregnancies are carried on the left horn, but it is well established now that maintenance of pregnancy is equal whether the ovulation occurs on the left or the right ovary (cf. Physiology).(117) Some of the possible etiologies of embryonic death in camelidae include: genetic or environmental factors, corpus luteum dysfunction, and uterine pathology such as infection or fibrosis.
Our observations, as well as those of others, show that there is an increase in embryonic death during the hottest months of the year.(75) Genetic abnormalities can be a cause of embryonic death but their incidence is usually low and they are difficult to diagnose with precision.
The corpus luteum is the main source of progesterone and its presence is required throughout pregnancy in camelidae (cf. Physiology). Therefore, any disturbance of luteal function due to abnormal corpus luteum or premature luteolysis would cause embryo loss. Luteolysis is normally caused in non-pregnant animals by a release of PGF2α from the uterus around day 11 in the dromedary and day 11 to 13 in alpacas and llamas. In order for this PGF2α release to be prevented, a normal embryo should be present in the uterus by day 9 post-breeding. Luteal dysfunction such as incomplete luteinization or short-life corpora lutea have been incriminated in the increased incidence of embryonic death due to inadequate progesterone levels. This is observed mainly in the case of multiple ovulation or when ovulation has been induced by exogenous hormonal treatment such as hCG.(83) Induction of multiple ovulation with Equine Chorionic Gonadotropin (eCG) usually results in many small corpora lutea and sometimes many embryos that can compete for space and lead to embryo death within the first 50 to 60 days of pregnancy.(43, 93) Abnormal luteal function has also been incriminated in the reduction of pregnancy rate in embryo transfer programs if the recipient has more than 6 corpora lutea per ovary.(75) Failure of the mechanism to prevent luteolysis can also be due to abnormal development of the conceptus or failure of migration of the conceptus to the left uterine horn. Migration of the conceptus can be hampered by the presence of intra-uterine adhesions or cysts. Luteolysis and embryonic death can also be consequent to systemic diseases or a local inflammation of the uterus. One common disease that leads to reproductive wastage in the dromedary is trypanosomiasis.(41)
Management errors
Management errors account for a high number of reported cases of infertility due to Repeat Breeding Syndrome. In a study conducted in the field we observed that 45% of all dromedary females presented for breeding had no follicular formation on the ovaries or only follicles smaller that 9 mm. Other management errors include: breeding with a young male, overuse of males, and lack of verification of intromission during copulation.
Diagnostic approach
Accurate diagnosis of the cause of repeat breeding relies on a multidisciplinary approach based on the history of the animal and the herd, clinical evaluation of the female, and laboratory findings. The owner should be warned that in order to obtain sufficient clinical data, a female suffering from repeat breeding may need to be monitored over several days to evaluate ovarian function and response to copulation. In the ideal case the female should be monitored over at least one reproductive cycle (from follicular growth to mating and pregnancy diagnosis) (Table 2).
History
The history of the animal and herd should provide a clear idea about the expertise of the owner in breeding camelidae as well as possible infectious causes that may affect fertilization rate and embryo survival. A history of previous breedings and behavior of the female as well as methods used for pregnancy diagnosis (clinical, behavioral, or hormonal) should be evaluated. Behavior is the most widely used method for the diagnosis of reproductive status by breeders. Refusal of the male or spitting off (llama and alpaca) and tail cocking (the dromedary) are the most widely-used signs of pregnancy. These signs are not 100% accurate but can provide valuable information on the date of embryo loss.
Clinical evaluation
Initial clinical evaluation of the female should give a base for future interpretation. This initial examination should involve at least rectal palpation, ultrasonography, vaginal examination, and uterine culture. If the history of breeding is accurate and the owner has a good experience in breeding, a uterine biopsy would be indicated especially if there is evidence of repeated early embryo loss or abortion, or if the female is old. The animal should be re-evaluated regularly to assess ovarian activity and response to ovulation stimulus. Under ideal conditions the female is examined every 2 to 3 days and follicular activity is monitored by ultrasonography. Decision to breed will be made when a mature follicle is present on one of the ovaries and the uterus is contracted. Clinical evaluation is continued after breeding to assess ovulation response to breeding and diagnose pregnancy. If ovulation has occurred an early pregnancy diagnosis should be scheduled 15 to 18 days after breeding. Pregnancy diagnosis can be done with very good accuracy by using ultrasonography or progesterone assay. For non-experienced practitioners, ultrasonographic pregnancy diagnosis should not be conducted before day 18 post-breeding. Once pregnancy has been confirmed the female should be monitored regularly to assess the health and development of the conceptus. Frequency of ultrasonographic monitoring of pregnancy varies according to practitioner. In the dromedary, we have been monitoring pregnancy weekly without any effect on fertility. This monitoring is important because the chance of determining the reason of pregnancy loss is increased if the female is re-examined soon after. When occurrence of ovulation has been ascertained, failure to detect a conceptus after breeding can result from lack of fertilization or embryonic death before day 15. Diagnosis of these situations will require more involved techniques such as collection of embryos in order to determine their quality and to evaluate uterine tube patency. It should be borne in mind that most of the embryonic loss in domestic animals is caused by either an infection or by degenerative changes in the endometrium. Therefore, cytological, bacteriological, and histopathological evaluation of the uterus should done as soon as possible after abortion or embryo loss.
Laboratory evaluation
The minimum reproductive laboratory data required on the first visit are uterine cytology and uterine culture. Detection of ovulation and evaluation of luteal function should be considered in the absence of obvious lesions of the genital tract which would prevent normal copulation. This evaluation is done by determining plasma progesterone level on a blood sample taking 4 to 5 days after mating for llamas and alpacas and 7 to 8 days after mating for dromedaries and Bactrian camels. Levels of progesterone equal to or higher than 2 ng/ml are compatible with the presence of a normal corpus luteum. The level of progesterone in the plasma remains higher than 2 ng/ml throughout pregnancy. Therefore any drop of progesterone below this level is an indication of early embryonic loss or unobserved abortion. In wild camelidae luteal function and pregnancy diagnosis can be monitored by measurement of progesterone metabolite in the urine or feces. Fetal health can also be monitored by determination of the concentration of estrone sulfate in blood or urine.(98, 120)
Definitive diagnosis and treatment
The approach described so far should enable the practitioner to rule out some of the probable causes of infertility. The definitive diagnosis can only be made when each segment of the reproductive tract is evaluated thoroughly. The practitioner should be familiar with all pathological processes that may have an affect in each of these segments in order to be able to make a list of differential diagnoses and design a follow-up strategy for a particular case.
Failure to maintain pregnancy
Failure to maintain pregnancy is obvious when an abortion has been observed. However, in most instances pregnancy loss is suspected when the female fails to show signs of advanced pregnancy (udder development, increased abdominal size) or fails to deliver at the due date. This can be due to unnoticed abortion, fetal maceration, or mummification. These pathologies are described in detail in special sections of this chapter.
Mating problems
Several mating problems are described in the female camelidae. In the dromedary, inability to complete breeding may be behavioral or physical. Non-acceptance of the female by a male or vice versa, is relatively common. The reasons for such a behavior are not clear. In these cases the breeding is best managed by the use of artificial insemination. Incomplete intromission and failure of ejaculation are also common in maiden females with persistent hymen or small genitalia. Physical mating inability can be due to the presence of congenital or acquired anomalies of the caudal part of the genital tract.
Observed anomalies
Reproductive consultation is obviously sought when there are visible lesions or anomalies of the genital tract such as in the case of abnormal vaginal discharge, prolapsed vagina, anomalies of the vulva, etc.. These problems are presented in detail in the study of the pathology of each part of the reproductive tract.
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