الفهرس 
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Abstract
Goat breeds were known for a long time ago as an important source of meat, milk, skins and mohair. Many reproductive changes constituted an impairment of healthy litters production. Among the causes which affect the reproductive efficiency, the chromosomal aberrations which have been recently studied. These aberration, now known to have a direct effect on fertility. The present investigation was carried out to study the structural and numerical aberrations of the chromosomes qualitatively and quantitively with their effects on fertility in goats also to establish the karyotypic picture of Balady goats in Egypt. The female goats (73 in goats, aged 3-4 years) were grouped according to their previous history of reproductive status and divided into four main groups:
A- 10 normal female goats used as control.
B- 20 female goats suffered from anestrum.
C- 20 female goats suffered from repeat breeding which in turn subgrouped into:
1-Subgroup I: those returned to estrous cycle more than three times (6 female goats).
2-Subgroup II : those returned to estrous cycle more than two times (9 female goats).
3-Subgroup III: those returned to estrous cycle more than one time (5 female goats).
D- 23 female goats suffered from abortion and also subgrouped into:
1-Subgroup I: 6 female goats with abortion more than three times.
2-Subgroup II: 6 female goats aborted two times.
3-Subgroup III : 11 female goats aborted one time. The chromosomal preprarations were made by the whole blood culture technique stained with Giemsa and 50 metaphases were examined the structural and numerical aberations in each animal, then the results were tabulated and statistically analysed. It was fou.nd that the karyotype of the goats examined included 29 acrocentric autosome pairs and a large acrocentric X- chromosome pair.
Chromosomal investigations of the control group showed that, the most frequent structural aberrations were deletions (8.20%) and centromeric attenuations (11.00%) with no numerical aberrations observed.
The anestrous group revealed that deletions (47.30%),
centromeric attenuation (33.90%), centric fusion (14.10%), breaks (12.40%) and rings (12.00%) were the most frequent structural aberrations found. On the other hand the predominent numerical aberrationes were monosomy (8.10%), trisomy (290%) and polyploidy (2.20%).
Concerning the repeat breeding group deletions (68.00%), centromeric attenuations (25.34%) and gaps (19.34) were the most frequent structural aberrations in those returned to estrus more than three times, while the numerical aberrations were monosomy (1.34%), trisomy (0.60%) and polyploid (0.66%). The repeat breeding goats returned to estrus more than two times showed deletions (47.34%), centromeric attenuations (24.44%), gaps (13.12%) rings (3.56%) and trisomy (1.34%). Somewhat lower frequencies (either structural or numerical) recorded in goats returned to estrus more than one time where the incidence of deletions were (34.00%), contromeric attenuations (24.40%) and monosomy (1.60%).
The aborted group showed deletions (67.34%), gaps (27.34%) and centromeric attenuations (24.00%) as the more frequent structural aberration recorded in goats aborted more than three times, while total monosomy (6.66%) was the only numerical aberration recorded. Only two cases (2.74%) with abortion more than three times were found to have 60, XX/59, X0 mosaics.
Also it was found that the structural aberrations in goats aborted two times showed an incidence of deletions (33.66%), centromeric attenuations (13.66%) and gaps (7.34%) and the numerical aberrations were polyploidy (2.34%), trisomy (1.66%) and monosomy (1.34%) while in goats aborted one time deletions (29.46%), centromeric attenuations (12.90%) and gaps (6.36%), were the most frequent structural aberrations found and monosomy (1.64%) and trisomy (1.28%) recorded as numerical aberrations.
It was shown from the present study that there was no significant differences in the mitotic index of the control group when compared with anestrous group and repeat breeding group while it was significant in comparing with the aborted ones. Also, significant increase in aborted group when compared with anestrous group and repeat breeding animals.
Concerning abnormal metaphases, there were significant decrease in the control group when compared to other abnormal ones. Also, it was obvious that, the total abnormal metaphases were directly related to the severity of fertility problems.