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Abstract
The present work aimed to:1. Compare the effectiveness of an estrus synchronization protocols based on GnRH
+ PGF2a (GP) combination.
2. A second aim was to obtain more information on the protocols, consisted of visually detecting estrus after synchronization of ovulation by (GP) or by PGF2a +GnRJ4+PGF2a (PGP)
3. Also to obtain an evaluation about the efficiency of the protocols consists of Timed Al after estrus synchronization and about the differences in conception rates particularly between Ovsynch and Cosynch protocols
4. Efficacy when reducing the dose of GnRH agonist.
5. Effectiveness of using Ovsynch in anestrous cows and efficiency of treatment on
--serum progesterone (P4) concentrations.
Fifty-One (51) comprised adult dairy cows and heifers (10 postpartum cross bread Holstein dairy cows aged 2-6 years old and 41 balady heifers 2 years old). The animals were classified into 6 groups according to the regimens suggested for Synchronization in each group.
1. Group A: (PGF2a-GnRH- PGF2a = PGP
12 heifers of 2 years age were injected with PGF2a at 0 day then injected with GnRH 14 days later then injected with 21b1 PGF2a dose after seven days. Animals were observed for estrus twice daily for 30 mm each time. Animal in estrus was inseminated with frozen-thawed semen from fertile bull
Immediately before treatment, ovarian structures were scanned by ultrasonography every other day until day of insemination and systemized blood samples were collected. Progesterone (P4)and Estradiol (E2) assayed : by enzyme immunoassay for the quantitative measurement
Results in group A (PGP) protocol.
Separate use of PGF2a administration whether at 0-day or day-2 I resulted into successful luteolysis in all cows and confirmed by drop in serum progesterone and rise in estradiol in day 23. While, the scans also have pointed to presence of CL at injection of 2nd PGF2a and presence of dominant follicle two days after injection.
In This group of cows the most efficient success in estrous synchronization depended mainly on PGF2a injection and GnRH has no role in the protocol.
The Conception rate in this group of cows was registered to be 70 % of inseminated cows and 58.3 % of all cows in group-A (12 cows). The breeding programs were based.pn estrous detection routine.
2. Group B: (GnRB-PGF2a) GP.
8 balady Heifers of 2 years age. Animals were injected with GnRH at 0 day then injected with PGF2cL 7 days later. Animals were observed for estrus twice daily
for 30 mm/each time. Standing estrus during routine handling was observed and estrus animal was inseminated with frozen-thawed semen from a single bull of high fertility.
Immediately before treatment, ovarian structures were scanned by ultrasonography every other day until day of insemination and Blood samples were collected. Progesterone (P4) and Estradiol (E2) assayed: by enzyme immunoassay for the quantitative measurement
Results in group B (GP) protocol
Result of applying this protocol showed that there was progressive gradual progesterone increase after GnRH treatment and throughout the first 48 hours (every 12 hours).
Fluctuation in estradiol concentrations were detected as indicated from great variations in standard errors of their values making them of insignificant
Ultrasonographic assessment of ovarian structures throughout this protocol have indicated presence of a follicle( 1cm 0) at the time of lS GnRH treatment (0-day) and showed a progressive decrease in diameter(0.33 cm 0) until day 4 (atretic follicle). Meanwhile 0-day Sonars have pointed to presence of growing CL showed a phase of progressive development until day-7 (day of PGF2a treatment) and luteolysis at day 9 of the protocol with emergence of growing follicle(new wave of follicular development).
3 out of 8 inseminated cows were found pregnant (37.5% Conception rate) low conception rate among this group could be pointed to improper protocol for estrus synchronization and improper estrus detection schedule
3. Group C: GnRH-PGF2ct- GnRH (Ovsynch half dose) = GPG
10 Holstein dairy cows (10 multiparous) were assigned at day 45 postpartum to receive Ovsynch program. Synchronization of ovulation was initiated at a random stage of the estrous cycle using half dose of GnRH\ 10 p.g Buserelin (2.5 ml Receptal®; Intervet) and full dose of PGF2cL. The hormones were scheduled as follows: day 0, GnRH (10 ig Buserelin); day 7 PGF2cL, 500 jig cloprostenol (2 ml estroPLAN) and Day 9, GnRH (10 jig Buserelin). All cows underwent a timed AT at 12 to 18 h after the second GnRI-I injection with frozen-thawed semen from a tested fertile bull. All inseminations were made by the same experienced technician.