Abstract
ABSTRACT The objective of this study was to quantify the superovulatory response and embryo production of Brazilian Bergamasca sheep and to evaluate the link to the follicular condition before superovulatory treatment, as a reference for selection of donors with potential for superovulation. Follicular population of twenty-three sheep was evaluated by ultrasound during metestrus phase of the estrous cycle and divided into groups of low, medium and high follicular population. Subsequently, they were synchronized, superovulated with 133mg of pFSH, mated and subjected to embryo collection. The superovulatory response (9.0±3.3 vs 10.7±6.2 vs 13.8±7.1) and embryo production (4.0±3.8 vs 2.6±2.0 vs 1,8±4.0) were similar between groups (P>0.05). There was a positive correlation between the number of follicles during the metestrus phase and the number of corpus luteum with premature regression (PLR) (0.52) and a negative correlation between the recovery rate and PLR (-0.44) (P<0.05). The sheep that presented PLR had more follicles during metestrus (16.9±7.8 vs 12.7±3.2) and lower embryo recovery rate (38.8±29.3 vs 72.2±29.9) than those with functional CLs (P<0.05). Follicular quantification during metestrus phases was unable to identify donors with high embryo production. Animals with PLR had a larger follicular population during metestrus and lower embryo recovery rate.
Highlights
Brazilian Bergamasca sheep were introduced in Brazil in the early 20th century, more precisely in the 1930s during the wave of Italian immigration
The results showed a superovulatory response ( 3 corpus luteum in both ovaries) in 82.61% (19/23) of Brazilian Bergamasca sheep submitted to the SOV protocol, presenting an average recovery rate of 52.10% (113 structures collected / 217 corpus luteum), where 46.20% of these structures were viable embryos, reaching an average of 2.26 ± 2.95 embryos per sheep collected
There are studies where 20 to 40% of the sheep did not respond to the treatment (D’Alessandro et al, 1996; Cordeiro et al, 2003). These results show the potential of Brazilian Bergamasca sheep in the use of assisted reproduction tools such as superovulation and embryo collection to support animal conservation and breeding programs
Summary
Brazilian Bergamasca sheep were introduced in Brazil in the early 20th century, more precisely in the 1930s during the wave of Italian immigration. They are large, white, flocked, polled, hardy sheep with dangling ears. Among the most used conservation methods is the preservation of gametes and cryopreserved embryos in germplasm banks (Mariante et al, 2011). In order to make the conservation of Brazilian Bergamasca possible, studies are needed to quantify the superovulatory response of these animals and to assist in the selection of donors with greater potential for embryo production, increasing the efficiency of conservation actions and reducing their cost
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