Suplementação com soro sanguíneo de vacas leiteiras em diferentes períodos de lactação na produção in vitro de embriões bovinos

Abstract

The transition period of dairy cows is characterized by several metabolic changes, leading to negative energy balance (NEB). NEB affects fertility in a negative way. The purpose of this work was to evaluate the effect of blood serum supplementation of dairy cows at different lactation periods in the maturation medium on the rates of nuclear maturation, cleavage and initial embryonic development. In 13 replicates, 1634 cumulus oocyte complexes (COCs) were collected and aspirated from ovaries of bovine females from local slaughterhouses. The COCs were randomly divided into three treatments containing 50 COCs each: SO: sheep serum used as control; FL: cow serum with 354 ± 3.8 days postpartum (pp) and PP: cow serum with 10.8 ± 4.8 days pp. Subsequently, the COCs were incubated at 39 ° C with 5% CO2 for 24 hours in the maturation medium according to the treatments. The insemination was carried out with a concentration of 1x106 spermatozoa / mL using mini-Percoll® gradient for spermatic selection. After insemination, the COCs were incubated for 18 hours. The zygotes remained in SOFaa culture medium under the same IMV conditions for 7 days. For analysis of nuclear maturation, four routines were used with a total of 320 oocytes which were collected after IMV, stripped and stained with Hoechst®. The time of insemination was considered as day 0, the cleavage was evaluated at day 3 and the overall embryonic development rate at day 7. According to the results no difference was observed in the number of oocytes that reached the stage of metaphase II between treatments. The cleavage rate was better in SO: 66.9% (368/577) than in PP: 47% (243/517) (P <0.05). Embryonic development was better at SO: 22.7% (131/577) when compared to FL treatments: 15% (81/540) and PP: 16.6% (80/517) (P <0.05). It was concluded that blood serum supplementation of cows at different lactation periods in the bovine oocyte IVM medium did not interfere with the rate of nuclear maturation, cleavage and early embryonic development with treatments FL and PP.