Appraisal of different protocols for estrus synchronization in local Rahmani sheep

ABSTRACT
This study was carried out to compare efficacy of using 4 different protocols on estrus
synchronization and reproductive performance of Rahmani ewes during mating season (May, 2015).
Seventy-five ewes aged 2.5- 3.0 years and weighed 47.42± 1.35 kg were used in this experiment.
Animals divided into 5 equal groups (15 each). Ewes of the first group (G1) served as a control.
Group two (G2) was exposed to vasectomized ram one week before start of mating season (ram
effect). CIDR device containing 0.3g progesterone was inserted for 12 days into ewes' vagina of
group 3 (G3), then ewes were injected with 500 IU PMSG at time of CIDR withdrawal. Meanwhile,
intravaginal sponges impregnated with 60 mg medroxyprogesterone acetate (MAP) were inserted for
14 days in ewes of group four (G4) and then injected with 500 IU of PMSG at time of sponges
withdrawal. Group five (G5) received double injections of GnRH, the first one (1 ml) on the first day
(0 day) and the second injection (1.5 ml) on day 11th, in addition to single injection of 125 μg PGF2α
on day 9 prior to the second injection of GnRH (GPG). All ewes groups were naturally mated on
time of standing estrus or at 72- 80 hour after treatment administration in case of ewes failed to show
estrus.
Results showed that percentages of estrus exhibition in hormonal treated groups G3, G4 and
G5 were significantly higher (80, 86.67 and 93.33%, respectively) than those in G1 and G2 (60 and
66.67%, respectively). Moreover, G5 (GPG) showed the highest percent of estrus comparing to G4
(sponges) and G3 (CIDR) groups. Estrus duration for G3, G4 and G5 were significantly longer
(43.20±15.92, 45.60±11.00 and 40.00±16.80 hours, respectively) than those of G1 and G2
(24.00±13.14 and 31.20±13.99 hours, respectively). The mean intervals from treatment to the onset
of estrus were significantly shorter in hormonal treated ewes of G3, G4 and G5 (3.60±0.87,
2.20±0.49, and 5.40±0.60 days, respectively) than those in G2 and G1 (12.80±2.63 and 17.20±1.65
days, respectively). Moreover, G5 (GPG) and G3 (CIDR) groups showed significant higher percent
of non- return to estrus (85.71 and 83.33%, respectively) than that observed in ram effect (G2) and
control (G1) groups (70 and 66.67%, respectively). The time to conception was significantly shorter
in G3, G4 and G5 than the control group (G1).
The number of large follicles of total ovaries was significantly low in ram effect group (G2)
compared to those in G3, G4 and G5, being the highest in G5. Moreover, hormonal treated ewes in
groups G3, G4 and G5 showed significantly higher total CLs numbers (1.00±0.32, 1.40±0.24 and
1.67±0.21/ ewe, respectively) than in ram effect and control groups (G2 and G1) (0.75±0.25 and
0.60±0.24/ewe, respectively), where it was the highest in G5 (GPG group).
Progesterone levels, recorded before treatments, were significantly lower in hormonal treated
groups G3, G4 and G5 (0.87±0.20, 0.77±0.70 and 0.80±0.59 ng/mL, respectively) than in G1 and
G2 (9.19±0.15and 3.86±1.07 ng/mL, respectively). Their levels decreased in all experimental groups
reaching minimal values at the onset of estrus (< 0.5 ng/ml). On day 30 post mating, G4 and G5
showed significantly the highest progesterone concentration comparing to other groups.
The pregnancy rate and number of lamb born/ ewe lambed were significantly the highest in G5
(80 and 127%, respectively) while the lowest in G1 (46.67 and 53.33%, respectively). In addition,
percentage of ewes lambed twins was higher in ewes treated with GPG protocol (G5, 58.33%)
followed by those treated with 500 IU PMSG after MAP (G4) and CIDR (G3) withdrawal (50 and
40 %, respectively).
In conclusion, GnRH– PGF2α– GnRH (GPG) protocol found to be more effective for estrus
synchronization than CIDR and MAP+ PMSG. Treatment of Rhamani ewes during summer season
with GPG protocol increased estrus and ovarian activities, as well as, pregnancy, lambing and
multiple birth rates.