Efeito da época do ano na transferência de embriões bovinos

Abstract

In order to study the effect of season changes in bovine embryo transfers (ET), the results of 397 ET, performed in 4 herds of different European breeds, located in 3 cities of the State of Minas Gerais were analyzed, considering 2 seasons: wet period (October to March) and dry period (April to September). The climatic charaterization of the different regions, using the average maximum temperature (Tmax) and the absolute preciptation (rain), demonstrated a similar climatic profile for all of them. Furthermore, climatic differences between wet and dry periods were demonstrated (p<0.05), revealing distinct enviromental conditions related to Tmax and rain. No variations were observed in the average number of recovered structures per flushing in the analysis between seasons or even between herds. The average number of viable structures did not vary among seasons or between breeds, but when the values of all breeds were considered together, a higher number of viable structures recovered in dry season was delected (p<0.05). Expanded blastocists, blastocists, and Young blastocists were the more often developmental stages of embryos recovered, respectivaly. Ther was no statistical variation for pregnancy rates in both analysis, between season or among breds, The relation between morphological classification and pregnancy rates was not coherent in the intermediate classes. Although climatic differences in annual seasons did not alter any parameter, the values of all breeds considered together showed that a higher number of viable embryos was recovered in the dry period. Additionally, the ET performance was not altered by the breed differences, as well.