Effect of royal jelly and GnRH on the estrus synchronization and pregnancy rate in ewes using intravaginal sponges

Abstract

The influence of natural royal jelly (RJ) paste and gonadotropin releasing hormone (GnRH) on reproductive responses of Awassi ewes was evaluated. In May 1998, 20 Awassi ewes (aged 2–5 years and weighing 52 kg) were treated with 40 mg fluorogestone acetate (FGA) impregnated intravaginal sponges for a period of 12 days. Half of the ewes were administered orally a total of 3 g RJ paste in 12 equal doses of 250 mg per day starting at FGA sponge insertion while the remaining half received no RJ paste. Ewes were exposed to two fertile Awassi rams from the time of FGA sponge removal (0 h, 0 day). Blood samples were drawn on alternate days from days 0 to 19. Five ewes per group (RJ and control) were randomly selected to receive a 50 μg GnRH injection 28 h post-sponge removal. No interactions were detected between RJ and GnRH. Incidence of estrus was greater (8/10 versus 4/10) in RJ-treated than in control ewes and intervals from 0 h to detected estrus were similar (45±4.1 h versus 55±6.7 h, respectively). Progesterone concentration increased on days 5–7 in all ewes and remained elevated through day 19 in 60% of the RJ-treated and 20% of the control ewes. These ewes lambed on average 149 days later and the number of lambs born was similar between the two groups of ewes. Regardless of RJ treatment, GnRH administration decreased ( P<0.05) the interval from cessation of treatment to estrus. The first rise in plasma progesterone occurred on day 5 in GnRH-treated compared with day 7 for non-GnRH-treated ewes ( P<0.05). The results demonstrate that RJ treatment in conjunction with a source of exogenous progesterone can be used to induce estrus and increase first service conception rate in sheep. Administration of GnRH reduced the interval to estrus and advanced plasma progesterone elevation.