Animal Reproduction (AR)
https://animal-reproduction.org/article/5b5a6081f7783717068b47d2
Animal Reproduction (AR)
Original Article

Effect of synchronizing ovulation in cattle administered a norgestomet ear implant in association with eCG and estradiol treatments on pregnancy rate after fixed-time embryo transfer

R.M. Ferreira, C.A. Rodrigues, H. Ayres, R.F. Mancilha, P.H. Franceschini, C.R. Esper, P.S. Baruselli

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Abstract

This study evaluated the effect of changing the day of administration of eCG and d-cloprostenol (PGF) and the replacement of estradiol benzoate (EB) with estradiol cypionate (EC) in fixed-time embryo transfer (FTET) protocols in order to simplify embryo recipient management. Three-hundred cycling heifers (Bos taurus x Bos indicus) were allocated to one of three groups. On a random day of the estrous cycle (D0), all groups received 2 mg of EB and an ear implant containing 3 mg of norgestomet, which was removed on D8. The control group (G-C; n = 100) received 400 IU of eCG and 150 µg of PGF on D5 and 1 mg of EB on D9. Group EB (G-EB; n = 100) received a similar protocol, but D5 treatments were postponed until D8. Group EC (G-EC; n = 100) received the same treatments as G-EB, except for the replacement of EB on D9 with 0.5 mg of EC on D8. Ultrasonographic determination of the number and area of corpora lutea (CLs) was performed on D17 for all groups and was followed by embryo transfer. Recipients with multiple CLs or a single CL ≥ 15 mm in diameter received an in vitro produced embryo. Pregnancy was diagnosed by ultrasonography 23 d after embryo transfer. Transferred-to-treated rate was similar among groups (G-C = 92.0%, G-EB = 93.0%, and G-EC = 96.0%). However, pregnant-to-transferred and pregnant-totreated rates were higher (P = 0.03) in G-EC [61.5% (59/96) and 59.0% (59/100)] than in G-C [45.6% (42/92) and 42.0% (42/100)] and G-EB [45.2% (42/93) and 42.0% (42/100)]. As expected, multiple ovulation rate (multiple ovulation-to-treated) in G-C (31.0%) was higher (P = 0.002) than in G-EB (11.0%) and G-EC (13.0%). In conclusion, the modifications to the conventional protocol of FTET reduced animal handling and increased pregnancy rates.

Keywords

fixed-time embryo transfer, norgestomet, pregnancy rate, eCG, estradiol cypionate
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