Alternatives to estrus synchronization and superovulation in ewes in the tropics
Neves, Jairo PereiraRamos, Alexandre FlorianiSilva, Bianca Damiani Marques
Background: With expansion of the market, sheep rearing has increased in Brazil, which means there an increase in the use of economically viable biotechnologies to increase production indices. The objective of this study is to show alternative protocols of oestrus synchronization and superovulation with the aim of increasing reproductive indices of sheep herds in the tropics. An alternative to the traditional protocol of MPA with eCG is the use of PGF2α. Review: Synchronization rate, hours between the end of protocol to estrus, size of largest and second largest ovarian follicles and ovulation rate did not differ between protocols (100.0%; 66.0 ± 2.5; 3.5 ± 0.2; 2.4 ± 0.2; 1.5 ± 0.1 and 100.0%; 67.3 ± 2.8; 3.1 ± 0.2; 2.2 ± 0.2; 1.7 ± 0.2 for PGF2α and MPA + eCG, respectively, P > 0.05). Ewes synchronized with MPA + eCG had higher serum P4 concentrations than ewes synchronized with PGF2α (3.9 and 2.8 ng/mL, MPA+ eCG and P4, respectively, P < 0.05). Based on these results, it may be concluded that the PGF2α was equivalent to traditional protocol in terms of estrus synchronization. Another alternative is the use of GnRH to induce ovulation. The use of GnRH associated with long (12 days) and short (7 days) protocol compared to no use showed efficient ovulation induction. Animals on the long + GnRH (36.4%) and short + GnRH (30%) showed lower estrus manifestation than long (80%) and short (90%), possibly due to induction of LH peak before estrus manifestation. In protocols that had GnRH injection, 100% of ewes ovulated, while 70% and 80% ovulated in long and short protocol without use of GnRH, proving that GnRH was efficient in inducing ovulation in these protocols. The interval between sponge withdrawal and estrus manifestation was the same (P > 0.05) among groups (37.0 ± 7.0; 44.2 ± 6.2; 42.0 ± 6.0; 45.6 ± 11.6 hours; for long + GnRH, long, short + GnRH and short, respectively). GnRH brought forward (P < 0.05). Similarly, no difference in number of viable embryos was observed between treatments (1.6 ± 2.0 e 1.7 ± 2.4 traditional and Day 0, respectively). Within viable embryos, the traditional protocol (0.4 ± 1.0) resulted in a higher (P < 0.05) number of morulae than that of the Day 0 protocol (0.1 ± 0.3). Conclusion: In summary, no difference in parameters evaluated was observed between both protocols. Considering the experiments all the alternatives protocols had the same efficiency that the traditional ones, could be alternatives to increase the reproduction in ewes.
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