Three cases of mare sterility with sex-chromosomal abnormality (63, X)

Abstract

Contents: Three mares that had heen diagnozed clinically as sterile were cytogenetically investigated. For each o f the mures 63 or more metaphases were analyzed (63 metaphases in one case, 72 metaphases in the 2nd case and 90 rnetaphases in the 3rd case). Only the sex chromosomal monosomy (63, X) were detected in each of the metaphases. Using the G‐banding technique unpairing X‐chromosomes, was accurately distinguished from autosomes nos. 1 and 2. The incidence of drumstick was 0.5 76 and 0.2 % respectively in two cases. The most obvious clinical abnormality was gonadal dysgenesis, which was observed in all mares. N o clear‐cut oestrus symptoms were detectable despite repeated treatment with various hormones.

X chromosome detection in an XO mare using a human X paint probe, and PCR detection of SRY and amelogenin genes in 3 XY mares

“…XO mares are usually smaller than the average of their breed. Other phenotypic traits of mares with X monosomy are expressed to a varied degree; a large head compared with body size, longer and more widely spaced ears and poor conformation due to hindlimb deformities (Hughes and Trommershausen-Smith 1977;Blue et al 1978;Miyake et al 1979;Mäkinen et al 1986;Breen et al 1997). In contrast to XO mares, 64,XY mares are of normal or slightly larger size and, in some cases, stallion-like conformational features have been observed (Bowling et al 1 9 8 7 ) .…”

Infertile mares with XO and XY sex chromosome deviations

“…The loss of oocytes is completed between the neonatal period and the first few years of life (Barad 1998). On histological examination in XO mares, the ovaries have been found to consist of undifferentiated ovarian stroma (Miyake et al 1979). In this study, the parental origin of the X chromosome could not be tested because the sire and dam of the mare in Case 1 were no longer alive.…”

“…Mares with XO and XY sex chromosomes usually do not show normal oestrous behaviour. However, mares showing irregular oestrous signs have been reported, and many affected mares have been able to be bred because a lack of progesterone production leads to a passive acceptance of the stallion (Miyake et al 1979;Long 1988;Bowling and Hughes 1993;Mäkinen et al 1999Mäkinen et al , 2001. Their external reproductive organs are normal, and on transrectal examination these mares are impossible to distinguish (Chandley et al 1975).…”

Monorchidism in a Phenotypic Mare With a 64,XY, SRY-Positive Karyotype

“…Human medicine was the first to adopt new DSD terminology and more recently veterinary medicine has trended towards classifying cases of abnormal sexual development according to the sex chromosome constitution of the animal [ 2 , 3 ]. Reports investigating DSD in the horse date back to the early 1970s [4][5][6] . Cases of DSD can have many different clinical presentations including, but not limited to Conflict of interest statement: The authors declare no conflict of interest.…”