Resumption of ovarian cycles of shami goat does throughout postpartum period using gnrh agonist and pgf2a analogue

الملخص EN

A total of 100 adult Shami goat does was used to determine the effect of early postpartum treatment with gonadotropin releasing hormone (GnRH) and/or prostaglandin F2? (PGF2?), on estrous and ovulation incidence as well as subsequent fertility.

Does were randomly allocated into four groups.

Does in groups 1 (G1) and 2 (G2) received 8 μg GnRH (Receptal) between day 10 and 14 postpartum while does in groups 3 (G3) and 4 (G4) were injected with saline solution.

Ten days later, does of G2 and G3 received 25 mg PGF2? (Lutalyse) and does in G1 and G4 received the same volume of saline solution.

Visual observation for signs of estrus throughout the day by the herdspersons were supplemented by two daily 30-min observations between 07:00 and 08:00 h and between 17:00 and 18:00 h.

Blood samples were collected thrice weekly via vein puncture from all does and continued until 6 weeks post mating or 120 days postpartum for progesterone assay.

Progesterone profile was used for characterization of estrus and ovulation.

All does were hand mated with 5 fertile bucks at the onset of the first estrus after 6 weeks postpartum and fertility in terms of non return to estrus, days open and conception rate were also recorded.

Results revealed that treatment with GnRH reduced intervals to first ovulation (P<0.05) and first detected estrus as well as increased the proportion of does with more ovulations before first service (83%) compared with saline treated group (57%).

Treatment with PGF2? reduced (P <0.05) intervals to second and third ovulation (20 and 19 day) as compared to G4 (26 and 27 day) group, respectively as well as shortened (P <0.05) interval to the first estrous cycle.

There was a numerical tendency of insignificant increases for G2 does (pre-treated with GnRH) to respond to PGF2? (45.0 vs.

35.0%) as well as decreasing percentage of those with no luteal function (20 vs.

25.0%), at the time of PGF2? treatment, than those of G4 treated does.

Does in G2 have the shortest (P< 0.05) interval to first estrus (35 days) compared to the other treated groups.

Interval to the second estrus was ranged from 22 to 26 day with differences being insignificant among treatments.

Percentage of does with cycles classified as short (<18) d), normal (18 - 24 d), or long (> 24 d) duration appeared similar, but when the ratio of normal to abnormal length cycles was examined, G1and G3 does showed more (P< 0.05) normal estrous cycles than G4.

The average frequency (number of estrus per doe) before either 6 weeks postpartum or first service was unaltered by treatment.

Treatment of does in G1 and G3 increased the proportion of does having estrous cycles of normal duration (P<0.05).

Days open, improved (P< 0.01) in the G1 and G2 groups compared with control (115 d, Table 7).

Days open in the G3 (96 d) were intermediate between the G4 and other treated groups.

Does of G1, and G3 showed less services for conception by 26 and 22% compared with G4.

Days open, Interval from kidding to conception, was reduced by 27-29 d (P <0.05) for does treated with either GnRH or PGF2? compared with control group.

The obtained results revealed that early resumption of ovulation and estrous cyclicity has been found in groups treated either with GnRH between d 10 and 14 (G1), or followed by PGF2? (G2) between days 20 and 24 as compared with control group (G4).

It could be concluded that treatment with GnRH or PGF2 2α, but not their combination, improved fertility of dairy goats.