Efficiency of Two Different Synchronization Protocols in Conception in Simmental Heifers

Abstract

This study aimed to reveal the effects of timed artificial insemination applied after the synchronization protocol known as day5 (D5) and the prostaglandin F2α (PGF2α) protocol applied in 11-day intervals (D11) on pregnancy rates in Simmental heifers. A total of 88 heifers were divided into two treatment groups. In the D5 group (n: 56), after gonadotrophin releasing hormone (GnRH) application, PGF2α injection was made on the 5th day and the second PGF2α injection was given one day later. The second GnRH was applied at the time of TAI and at the 44th hour of the second PGF2α application. In the D11 group (n: 32), double-dose PGF2α was given in 11-day intervals. GnRH was applied at the time of TAI and at the 81st hour following the second PGF2α injection. Pregnancy-associated glycoprotein visual test was carried out for determining to pregnancy on the 28th day. Additionally, for the purpose of determining embryonic deaths, the pregnancies were checked again by ultrasonography on the 63rd day following TAI. The 28th-day pregnancy rates in the synchronized heifers were 51.8% (29/56) in the D5 group and 43.8% (14/32) in the D11 group P>0.05. The 63rd-day pregnancy rates were 48.21% (27/56) in the D5 group and 40.62% (13/32) in the D11 group P>0.05. Consequently, although there was no statistically significant difference in terms of pregnancy rates between the D5 and D11 protocols, there was a numerical increase in the D5 protocol. Considering its short application time, D5 may be used for TAI in Simmental heifers.