Comparison of four synchronization protocols for fixed-time bovine embryo transfer in Bos indicus x Bos taurus recipients.
The objective was to evaluate the effects of 400 IU of eCG given on Days 5 or 8 of an estrus synchronization protocol with progesterone-releasing intravaginal devices (PRID) and estradiol benzoate (EB), in recipients for fixed-time embryo transfer. A secondary objective was to determine the effects of injectable progesterone (given concurrent with EB treatment). Three-hundred-and-four crossbred Bos taurus x Bos indicus beef heifers were randomly assigned to one of four treatment groups (2 x 2 factorial design). At unknown stages of the estrous cycle (Day 0), all heifers received a progesterone-releasing intravaginal device (PRID), plus 2mg of EB i.m., with or without a concurrent treatment of 50mg of progesterone i.m. Heifers were further subdivided to receive 0.15 mg of d-cloprostenol (PGF) i.m. and 400 IU of eCG i.m. on Days 5 or 8. In all heifers, intravaginal devices were removed on Day 8 and 1mg of EB was given i.m. on Day 9 (Day 10 was arbitrarily considered the day of estrus). On Day 17, all heifers with >1 CL or a single CL with a diameter > or =18 mm (based on ultrasonographic examination), received an in vitro produced (IVP) embryo by non-surgical transfer. On Day 17, there was an effect of day of eCG administration on the number of CL (1.35 +/- 0.08 versus 1.13 +/- 0.04, for Day 5 versus Day 8, respectively; P = 0.02) and (in a subset of 154 heifers) mean (+/-S.E.M.) plasma progesterone concentrations (2.41 +/- 0.26 versus 1.74 +/- 0.19 ng/mL; P = 0.03). Although the proportion of recipients transferred/treated and pregnant/transferred did not differ among groups, the proportion of recipients pregnant/treated tended (P = 0.1) to be higher in heifers treated with eCG on Day 5 versus Day 8 (47.0% versus 40.7%, respectively). Progesterone treatment had no significant effect. In conclusion, treatment with eCG (and D-cloprostenol) on Day 5 significantly increased the number of CL and plasma progesterone concentrations and tended to increase pregnancy rates, although progesterone treatment had no significant effect.
Nasser
L F
LF
Departamento de Reprodução Animal, FMVZ-USP, CEP 05508-000 Saã Paulo, Brazil.
Reis
E L
EL
Oliveira
M A
MA
Bó
G A
GA
Baruselli
P S
PS
D000282:Administration, Intravaginal; D000818:Animals; D002417:Cattle; D006063:Chorionic Gonadotropin / Q000008:administration & dosage; D003008:Cloprostenol / Q000008:administration & dosage; D004343:Drug Implants; D004624:Embryo Transfer / Q000662:veterinary*; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D006064:Gonadotropins, Equine / Q000008:administration & dosage; D011247:Pregnancy; D011374:Progesterone / Q000008:administration & dosage / Q000097:blood; D013997:Time Factors
D006063:Chorionic Gonadotropin; D004343:Drug Implants; D006064:Gonadotropins, Equine; D003008:Cloprostenol; D011374:Progesterone