الفهرس 
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Abstract
This study investigated three synchronization protocols with FTAI on the fertility of crossbred cows. Ninety one cows were assigned to four groups where the body condition score (BCS), age distribution, parity and average daily milk yield were apparently even among groups then each group received 1 of 4 treatments: (1) Ovsynch-CIDR treated cows (n = 24) were synchronized with 10 µg (GnRH, IM) with insertion of controlled internal drug release device (CIDR) on Day 0 followed by 500 µg prostaglandin F2α and CIDR removal on Day 7. On Day 9 cows received 10 µg GnRH followed by FTAI 18 h later, (2) PGF2α treated cows (n = 25) received double doses of 500 µg PGF2α 12 days apart followed by FTAI 80 h after the second dose of PGF2α, (3) Ovsynch treatment (n = 17) with 10 µg GnRH-Day 0, 500 µg PGF2α-Day 7 and 10 µg GnRH-Day 9 sequence followed by FTAI 18 h later and (4) Untreated cows (Control, n = 25). Our results revealed that pregnancy rate was greater (p˂0.05) in PGF2α (36%), compared with Ovsynch (29.4%), Ovsynch-CIDR (20.8%) and control (12%) cows. In conclusion, acceptable pregnancy rate can be achieved with FTAI after 80 h of synchronized cows with double doses of PGF2α 12 days apart compared with synchronization of ovulation with (Ovsynch-CIDR) or without (Ovsynch) P4 supplementation.