| Dissertation note |
The main objective of the present study is to compare the two synchronization protocols (Ovsynch vs 2PG) on estrus response, follicular development, ovulation, pregnancy rate and fecundity in Beetal and Teddy breeds of Pakistan. The secondary objective is to determine the efficacy of GnRH at the time of breeding on pregnancy rate in Beetal goats. Experiment 1 was conducted with a total of 28 goats during breeding season (September-October) at Livestock Production Research Institute, Bahadurnagar, Okara. The goats were randomly allocated in one of two treatment groups, Ovsynch and two PGF treatments. The Ovsynch treated does received an intramuscular injection of GnRH analogue 12.5µg lecirelin (Dalmarelin®, Fatro, Italy), on "Day 0". On "Day 7" does were treated with injection of PGF2? analogue 37.5µg d-cloprostenol (Dalmazin®, Fatro, Italy,) followed by a second injection of 12.5µg lecirelin (Dalmarelin®, Fatro, Italy), after a 48h period. Animals in the double PGF group received two injections of 37.5µg d-cloprostenol (Dalmazin®, Fatro, Italy), 10 days apart. In order to determine the estrous response and its duration, two aproned bucks were used twice daily for 30 minutes after the last PGF2? injection in both groups until the termination of estrous signs. All goats were naturally bred 12h after the onset of estrus. Follicular and luteal activity was monitored by transrectal Ultrasonography (ALOKA, SSD 900 Japan) with the aid of a 7.5-MHz linear array transducer daily- from the start of treatment, until estrus and then twice a day until the cessation of large follicles (apparent ovulation). On day 7 after breeding, all goats were re-examined by transrectal ultrasonography to determine the ovulation rate, based upon the number of CL's present. Pregnancy rate and fecundity (no of embryos per doe) was again determined at Day 30 after breeding by transrectal ultrasonography. Experiment 2 was performed on 25 goats. These does were randomly allocated to two groups (GnRH, n=11 and Control, n=14). GnRH does received 12.5µg lecirelin on the day of natural breeding (12h after standing estrus), while the control does did not receive any treatment. Timing of ovulation, pregnancy rate and fecundity were assessed by transrectal ultrasonography as in Experiment 1. Estrus (Experiment 1) was detected in 10 out of 14 does (71%) in Ovsynch group, while all 14 goats (100%) of double PGF responded group. The interval from the last PGF injection to estrus was 48.0 ± 2.6h in the Ovsynch group, while 36.0 ± 1.2h in the double PGF group (P<0.05). The interval from the last PGF injection to ovulation did not differ significantly between the Ovsynch (73.0 ± 4.8h) and double PGF (66.0 ± 2.7h) groups respectively. Similarly the interval from standing estrus to ovulation was not significant between the Ovsynch (24.0 ± 3.7h) and double PGF (30.0 ± 2.7h) treatments respectively. Estrous duration was similar in both treatment groups (44.7 ± 4.9h for Ovsynch and 47.1 ± 2.9h for the 2PGF). The size of ovulatory follicle was similar in both treatment groups (Ovsynch, 7.1 ± 0.2mm; 2PGF, 7.1 ± 0.1mm). On day 7 after breeding, the ovulation rate (no. of CL's on the ovary) were similar in both the Ovsynch (1.6 ± 0.2) and double PGF (2.0 ± 0.2) groups. The pregnancy rate as determined by transrectal ultrasonography on day 30 (Fig. 1) revealed 6/10 (60%) in the Ovsynch and 11/14 (78%) in the double PGF groups respectively (not significant). Fecundity was similar for both treatment groups (1.6 ± 0.2). In Experiment 2 the interval from standing estrus to ovulation recorded was not significant (31.2 ± 2.9h and 36.0 ± 5.3h), the ovulatory diameter (6.8 ± 0.1mm, 7.2 ± 0.5 mm (P<0.05), the pregnancy rate (54% (6/11) and 64% (9/14), and fecundity (1.5 ± 0.5, 1.7 ± 0.5) were not significant between GnRH treated and control does respectively (Table 2). From these experiments it can be concluded that the Ovsynch protocol, which is a non-steroidal and safe approach for estrous synchronization appears to be similar to the double PGF injection protocol, in terms of the reproductive performance in goats. However, this needs to be tested on larger number of animals. Furthermore, the use of GnRH at the time of breeding does not improve the reproductive performance in goats. The data generated has important implications for commercial goat farming in the developing countries.
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