ESTUDO RETROSPECTIVO DE FATORES QUE INTERFEREM NA FERTILIDADE DE VACAS RECEPTORAS DE EMBRIÕES

Abstract

The aim of this study was to identify critical points that have negative impact on fertility of bovine embryo recipients. In the experiment were used 6527 reproductive data from embryo recipients of a farm located in the state of São Paulo during the years 2000-2004. Data were analyzed using the Statistical Analysis System for Windows (SAS, 2001), by multivariate logistic regression using the LOGISTIC procedure of SAS. Variables were removed by reverse elimination, according to Wald„s statistical criteria with stipulated value P> 0.20. The final statistical model included the variables of quality of corpus luteum, embryo development, embryo quality, biotechnology‟s type used (TE-SOV or OPU- IVF) and number of transfer [repeat breeders (> 3 embryos transferred) or not repeat breeders]. After this initial analysis, the variables were analyzed for the binomial distribution using the GLIMMIX procedure of SAS. There was no interaction between these variables (P>0.05). In the study, it was found that the pregnancy rate was influenced by the number of embryos transferred in defined receptor [not repeat breeders (35.7%, 2019/5650) and repeat breeders (32.0%, 281/877); P=0.001], by the stage of embryonic development [morula (42.0%, 748/1782)a, by the early blastocyst (31.7%, 292/921)b, blastocyst (32.0%, 402/1224) and expanded blastocyst (32.8%, 790/2412)b; P=0.01], the quality of the corpus luteum [CL1 (35.7% (1631/4571); CL2 (36.2%, 458/1266) and CL3 (31.3%, 174/556), P=0.01] and type of embryo‟s production [fresh embryos produced in vivo (47.4%, 509/1074)a, the frozen embryos produced in vivo (38.8%, 590/1520)b and embryos produced in vitro, (30.3%, 1175/3875)c, P=0.001]. However, the pregnancy rate was not influenced by season [summer - November to February (35.8%, 596/1665) and winter - April to July (33.4% (945/2830), P=0.85] by sync donor/recipient [D-2 (39.7%, 418/1053), D-1 (34.5%, 1100/3189), D0 (35.5%, 639/1798), D+1 (29.4%, 143/487); P=0.13], by the side of transfer [right side (35.0%, 1398/3991) and left side (35.6%, 901/2534), P=0.98]. We concluded that fertility in recipient embryos is influenced by multiple factors in which there was less fertility in repeat breeders‟ receptors, in embryos up to the morula stage, low quality of the corpus luteum, and in frozen or in vitro produced embryos.