الفهرس 
Chapter I : IntroductionOnly 14 pages are availabe for public view
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Abstract
The present study was conducted on 53 mature bucks ( 36 V. Line and 17 Gabali breeds ). It was performed during the breeding season from September 2003 to Marsh 2004. The animals were aging 7-23 months and weighing 2.8-4.5 kgs. Semen evaluation were done for all bucks, then bucks were classified to 4 categories according to the farm records for more histopathological and cytogenetic studies as follow:
1-The first category: bucks with high reproductive performance:
This category consisted of 6 bucks representing group I and used as control group.
2-The second category: bucks with moderate reproductive performance:
In This category bucks were 9 in number (6 representing group II and 3 representing group III).
3- The third category: bucks with low reproductive performance:
Bucks of This category were 8 in number (5 representing group IV and 3 representing group V).
4- The fourth category: bucks with no sexual interest:
This category consisted of 3 bucks representing group VI and had no response to females.
Statistical analysis of semen evaluation in addition to histopathological finding and cytgenetic analysis revealed the following results:
VI.1. Reaction time and semen characters:-
The reaction time of the first and second ejaculates for all groups of bucks is significantly much longer in the 5th group (78.60 seconds) than that recorded for the 1st , 3rd and 4th groups (11.15-16.83 seconds). The shortest reaction time is mentioned for the 2nd group of bucks (6.56 seconds). In general, the reaction time appeared shorter for the first (6.13-14.18 seconds) than the second ejaculate (7.00-21.56 seconds) in the 1st , 2nd , 3rd and 4th groups.
It was found that the ejaculate volume of the first ejaculate (0.64-0.88 ml) is larger than the second ejaculate (0.47-0.74 ml) for the 1st , 2nd , 3rd and 4th groups. Irrespective of sequence of ejaculation, the overall mean ejaculate volume of 2nd , 3rd and 4th groups (0.68-0.79 ml) appeared significantly larger than that observed for the 1st and 5th groups (0.48-0.56 ml).
The maximum PH of buck’s semen was recorded in 2nd and 4th groups (8.24-8.41) which significantly increased than in 3rd and 5th groups (7.88-8.02). The lowest PH was recorded for 1st group (7.53). Moreover, the PH of the first ejaculate (7.67-8.50) is elevated than that recorded for the second one (7.40-8.31).
There was a non significant variation in mass motility of the first and second ejaculates in the 1st , 2nd , 3rd and 4th groups. Irrespective to the sequence of ejaculation, the mass activities were recorded for the 1st and 2nd groups (2.86-2.87) followed by the 3rd , 4th and 5th groups (1.00-2.30).
The individual sperm motility of the second ejaculate (24.12-80.00%) is better than in case of the first one (18.82-72.78%) for the 1st, 2nd, 3rd and 4th groups. Irrespective to the sequence of ejaculation, The best individual sperm motility was recorded for the 1st and 2nd groups (74.38-75.00 %), followed by significant reduction for the 3rd and 5th groups (53.86-55.00 %). The lowest individual sperm motility was observed for the 4th group (21.47%).
The live sperm percentage for the second ejaculate (29.88-85.89%) were appeared much higher than that recorded for the first one (25.82-80.22%) in the 1st , 2nd , 3rd and 4th groups. Irrespective to the sequence of ejaculation, The maximum live sperm percentage recorded for the 1st and 2nd groups (82.94-83.06 %), followed by the 3rd and 5th groups (60.80-62.36 %). A sharp significant decrease in the live sperm percentage was reported in the 4th group (27.85 %).
The sperm cell concentration was significantly increased in 1st and 2nd groups (271.44-304.00 X106 sperm / ml) followed by 3rd and 4th groups (226.27-232.97 X106 sperm / ml). The minimum sperm cell concentration was recorded in 5th group (201.60 X106 sperm / ml). However, there was no significant variation in sperm cell concentration between the first and the second ejaculates in each group.
In general primary sperm abnormalities were significantly increased in 4th group and 5th group (13.60-29.38 %) than in case of 1st, 2nd and 3rd groups (5.06-9.45 %). The proximal protoplasmic DROPlets was significantly elevated in 4th group (8.35 %) followed by that recorded in 3rd and 5th groups (3.82-4.80). The lowest percentage of the proximal protoplasmic DROPlets was recorded in 1st and 2nd groups (0.83-1.19 %). Percentage of distal protoplasmic DROPlets was significantly elevated in 4th group (9.03 %) followed by 3rd and 5th groups (3.80-4.59 %). The lowest percentage of distal sperm abnormalities was observed in 1st and 2nd groups (2.38-2.56 %). Percentage of secondary sperm abnormalities was sharply increased in 4th group (18.21 %) followed by 3rd group (8.14 %) when compared with that recorded for 1st, 2nd and 5th groups (5.22-5.60 %). The maximum percentage of total sperm abnormalities was observed in the 4th group (64.97 %) followed by that mentioned in the 3rd and 5th groups (26.00-27.80 %) and the minimum percentage was recorded in the 1st and 2nd groups (14.00-4.22 %). However, there was no significant variation in different upon mentioned abnormalities between the first and the second ejaculates in each group.
VI.2. The histopathological study:
The microscopic examination of testis of bucks in 1st, 2nd and 3rd groups revealed non pathological changes in seminiferous tubules (S.T.) that were filled with numerous mature spermatozoa in their lumen. Meanwhile, the histopathological examination of their epididymides showed normal histological structure and filled with aggregated sperms.
The histopathological findings of the examined testes of bucks in 4th and 5th groups were characterized by severe testicular degeneration their epididymides were characterized by presence of few degenerated sperms and eosinophilic cellular debris in their lumen.
Microscopic examination of testis of bucks in 6th group showed extensive necrosis of S.T. Moreover, the examined epididymides of these bucks showed degeneration of their lining epithelium with aggregation of few dead sperms within the lumen of tubules
VI.3. Cytogenetic analysis:
Chromosomal map of normal bucks revealed the presence of 22 pairs (2N) of chromosomes. These chromosomes karyotyped as 6 pairs metacentric, 6 pairs submetacentric (one pair of them is sex chromosomes (XY), 6 pairs telocentric and 4 pairs acrocentric. The results showed that (33.30%) of bucks showed minimal chromosomal aberrations respented by centromeric attenuation, deletion, ring chromosomes and hypoploidy (0.33-0.66%).
Examination of bucks of 2nd group showed 100% chromosomal abnormalities. Structural aberrations were represented by centromeric attenuation, deletion, ring chromosomes, break, end to end association, pulverisation and sticky chromosomes (1.33-22.22 %). Numerical aberrations that represented by hypoploidy and polyploidy (4-12.33%).
Additionally, all bucks of 3rd group showed structural abnormalities represented by centromeric attenuation, deletion, ring chromosomes, break, end to end association, pulverisation and sticky chromosomes (1.33-17.33 %). Moreover the numerical aberrations represented by hypoploidy and polyploidy (0.66-2.66%).
Cytogenetic analysis of bucks of 4th group showed that 60% of bucks had chromosomal abnormalities while 40% of bucks were free from any chromosomal aberration. Structural abnormalities were represented by centromeric attenuation, deletion, ring chromosomes, break, end to end association, pulverization and sticky chromosomes (1.2-11.2%), beside the numerical aberrations which were represented by hypoploidy (6.4-8%) and polyploidy.
In the same respect examination of bucks of 5th group showed that 100% of bucks had chromosomal abnormalities. Structural aberrations were represented by centromeric attenuation, deletion, ring chromosomes, break, end to end association, pulverisation and sticky chromosomes (4-28%). In addition to numerical aberrations that represented by hypoploidy (%) and polyploidy (13.33-16.66%).
Analysis of bucks of 6th group revealed that 100% of them had chromosomal abnormalities. Structural abnormalities were represented by centromeric attenuation, deletion, ring chromosomes, break, end to end association, pulverisation and sticky chromosomes (1.2-26%), beside the numerical aberrations which were represented by hypoploidy and polyploidy (14.6-18.6%).