الفهرس 
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Abstract
It is better to identify predictors and genetic markers to improve semen quality and fertility of buffalo bulls. This study aimed to identify the genetic polymorphism of Sex determining factor (SRY), Aquaporin 7 (AQP7) and Osteopontin (OPN) genes by the restriction fragment length polymorphism (RFLP), the single strand conformation polymorphism (SSCP) and the nucleotide sequencing, and to find out the associations of semen quality with field fertility of the Egyptian buffalo bulls. The first investigation aimed to determine the genetic polymorphism of SRY gene and the association of fresh semen criteria with field fertility of buffalo bulls. About 264 fresh semen ejaculates from 66 bulls were collected and evaluated. The bulls with ejaculates < 60% motility (n= 10) were excluded from insemination. The inseminating bulls (n= 56) were categorized according to pregnancy rate (PR) into high (PR≥50%, n=49) and low (PR<50%, n=7) fertile. A fragment of SRY gene (228 pb) was amplified by PCR. The genetic polymorphism of SRY gene was identified by RFLP, SSCP and sequencing. A significant negative correlation (r=-.369, P< 0.01) was shown between sperm abnormalities % and PR whereas a significant positive correlation (r=.273, P< 0.05) was obvious between live sperm % and PR. However the SRY gene showed no genetic variation in all bulls. The second investigation aimed to detect the genetic polymorphism of AQP7 gene with the in-vivo fertility of Egyptian buffalo bulls. Fresh semen ejaculates (n=188) from 47 buffalo bulls were collected and evaluated. The bulls were grouped according sire conception rate (SCR) into high (SCR≥50%, n=41) and low (SCR<50%, n=6) fertile bulls. A fragment of exon 3 of AQP7 gene (200 bp) was amplified by PCR. The genetic polymorphism of AQP7 gene was detected by RFLP, SSCP and sequencing. SCR was significantly (p<0.001) increased in high (71.4±1.3) than low (44.7±2.8) fertile bulls while semen parameters showed a non-significant differences. No genetic variation in AQP7 gene was observed in all bulls. The third investigation aimed to investigate the genetic polymorphism of OPN gene and the quality of fresh semen in buffalo bulls. Fresh semen ejaculates (n=228) for 57 bulls were collected and evaluated. The bulls’ semen was grouped according to the individual motility into high (≥60%, n=47) and low (<60%, n=10) quality. A fragment of intron 3 of OPN gene (250 bp) was amplified by PCR. The genotyping of OPN gene was demonstrated by RFLP and SSCP. Our findings revealed that, the high-quality semen was significantly increased in individual motility % (p<0.001), live sperm % (p<0.001) and sperm concentration (p<0.05) than the low quality. Also, the monomorphic pattern of OPN gene in all bulls was noticed. Three nucleotide insertions (T 44, A49 and A62) and two substitutions (G11>C and A108>G) were clear by sequence alignment with buffalo OPN gene in GenBank.