180 PREGNANCY LOSS (BETWEEN 30 AND 60 DAYS) IN HIGH-PRODUCING REPEAT-BREEDER HOLSTEIN COWS SUBMITTED TO EMBRYO TRANSFERC. A. Rodrigues A , A. A. Teixeira B , R. M. Ferreira B , H. Ayres B , A. L. Ranieri C , B. G. Freitas B and P. S. Baruselli B
A Clínica Veterinária SAMVET de São Carlos Ltda, São Carlos, SP, Brazil;
B Universidade de São Paulo, São Paulo, SP, Brazil;
C Universidade Estadual Paulista, Jaboticabal, SP, Brazil
Reproduction, Fertility and Development 22(1) 248-248 http://dx.doi.org/10.1071/RDv22n1Ab180
Published: 8 December 2009
Reproductive efficiency has a major impact on profitability of dairy farms. Pregnancy loss in cattle is one of the major impediments for adequate reproductive performance. The aim of the present study was to evaluate factors associated with pregnancy loss between 30 and 60 days of gestation in high-producing repeat-breeder (>4 services) Holstein cows submitted to embryo transfer (ET). A retrospective analysis was performed using data from 1 commercial dairy farm, located in Descalvado, Brazil (22°01′27″S; 47°53′19″L). Overall, 2096 ET were analyzed from 2004 to 2008. High-producing Holstein cows from the same herd were used as embryo donors. Embryos were produced by superovulation using the same protocol (8 decreasing injection of FSH) and were transferred, either fresh or frozen-thawed, to repeat-breeder Holstein recipients 6, 7, or 8 days after estrus (synchrony of Day 1, Day 0, or Day 1 with the donor, respectively). Statistical analysis was performed using PROC GLIMMIX of SAS (SAS Institute Inc., Cary, NC, USA). Variables included in the model were synchrony between recipient and donor at ET day, fresh and frozen-thawed embryos, stage of embryo development, and embryo quality. All cows were examined for pregnancy by ultrasonography 23 and 53 days after ET (30 and 60 days of pregnancy). There was no effect of year. The pregnancy loss was greater (P = 0.005) for fresh (22.9%, 141/615) v. frozen-thawed embryos (19.4%, 288/1481). Also, pregnancy loss was influenced (P = 0.002) by the synchrony between recipient and donor at ET day [Day -1:18.3% (53/290); Day 0: 18.9% (233/1234); D1: 24.9% (144/578)]. However, there was no difference in pregnancy loss when the stages of embryo development [morula: 20.7% (295/1428); early blastocyst: 18.9% (67/355); blastocyst: 23.0% (59/256); expanded blastocyst: 14.0% (8/57; P = 0.31)] and embryo quality [grade 1: 17.6% (78/443); grade 2: 20.1% (216/1073); grade 3: 23.3% (135/580); P = 0.31] were compared. In conclusion, pregnancy loss was greater in high-producing repeat-breeder Holstein cows receiving fresh embryos compared to frozen-thawed embryos and when Day 1 recipients were used compared to Day -1 and Day 0.