Production of prolific microsheep by embryo transfer into large non-prolific sheep.

The Garole is a prolific breed of microsheep that possesses the FecB gene, which increases ovulation rate. The purpose of this study was to compare embryo production by multiple ovulation in seven Garole ewes with that in seven normal size, non-prolific Malpura ewes, and assess the influence of the large body size of Awassi crossbred recipient ewes on the birth-weight of Garole lambs. Oestrus was synchronised with two intramuscular injections of 7.5 mg prostaglandin F(2alpha) administered 10 days apart. The donor ewes were superovulated by the use of pregnant mare serum gonadotrophin and follicle-stimulating hormone. The onset and duration of oestrus were similar in both breeds. The Garole donors had higher total mean (se) ovarian responses (15.6 [3.6] v 9.1 [2.3]), ovulation rate (13.6 [3.1] v 8.4 [2.2]) and produced more transferable embryos (6.0 [3.5] v 4.0 [0.9]) than the Malpura donors, but the differences were not statistically significant. The Garole lambs produced by embryo transfer were on average 57.8 per cent heavier at birth than contemporary Garole lambs produced by natural mating.

Effect of two doses of progesterone on estrus response and fertility in acycling crossbred Bharat Merino ewes in a semi-arid tropical environment.

The efficacy of two doses of progesterone (P4), i.e. 350 and 300mg was evaluated in acycling crossbred ewes (50) during the autumn breeding season. Ewes were treated with intravaginal progesterone sponges with either 350mg or 300mg for 12 days. At standing estrus, ewes were hand mated (three cycles). Progesterone (350mg) gave a better (P<0.05) estrus response (75%), compared to 300mg dose (42%). Ewes treated with 350mg P4 also showed better (P<0.05) synchronization response (93%) than those treated with 300mg (56%) at 72h after sponge removal. Lower doses of progesterone (300mg) significantly delayed (P<0.01) the onset of estrus. However, dose had no significant influence(P>0.05) on estrus length, conception rate and the proportion of ewes lambing at term. This study indicates that dose of progesterone may have an effect on estrus exhibition and response time without altering the conception rate and lambing in acycling crossbred Bharat Merino ewes during the major breeding season in a semi-arid tropical environment.

The effect of gonadotrophin releasing hormone and follicle stimulating hormone in conjunction with pregnant mare serum gonadotrophin on the superovulatory response in crossbred sheep in India.

Thirty-two mature crossbred (Fine Wool Synthetic, FWS) sheep developed for fine wool production in India were treated for superovulation and oestrus synchronization in spring season. The ewes were randomly allocated to four treatment groups in a factorially designed experiment. For induction of superovulation, pregnant mare serum gonadotrophin (PMSG) was administered alone (group 1), in combination with gonadotrophin releasing hormone (GnRH) (group 2) or with follicle stimulating hormone (FSH) (group 3) and with both (group 4). Oestrus was synchronized in all the ewes by two injections of prostaglandin F2 alpha (PGF, 10 mg each) administered at an interval of 10 days. Superovulation treatment started 48 h prior to the second PGF injection. The proportion of ewes in oestrus did not differ significantly (p > 0.05) in the four groups. The use of GnRH set the ewes into oestrus earlier than the ewes in the other groups. Treatment with PMSG (800 IU) in conjunction with 4 micrograms of Buserilin (GnRH) increased the ovulation rate (9.1 +/- 2.6 corpora lutea (CL)) above that observed when PMSG was used alone (3.0 +/- 0.7 CL). The use of FSH (0.5 U ovagen) in conjunction with PMSG was characterized by a decrease in the proportion of ewes with < or = 2 CL (4/8 vs 7/8; p < 0.05) and in the number of ovulations, i.e. CL observed (2.4 +/- 0.6 vs 9.1 +/- 2.6), and a nonsignificant increase in the incidence of large follicles (LF) (4.6 +/- 1.28 vs 3.25 +/- 0.6; p > 0.05). The interaction between treatments of FSH and GnRH was not significant (p > 0.05). It is concluded that use of GnRH, in conjunction with either PMSG alone or PMSG plus FSH treatment, advanced the onset of oestrus and increased the ovulation rate in FWS sheep.