Produção in vitro de embriões bovinos de doadoras zebuínas (Bos indicus) e taurinas (Bos taurus)

Abstract

The aim of the present study was to evaluate the effect of race on the in vitro production of bovine embryos from zebu and taurine donors. The cumulus-oocyte complex were obtained from 167 Bos taurus donors and 161 Bos indicus, was performed using phosphate-buffered saline at 36 °C added heparina and then oocytes were classified as grade I, II, III (GI, GII, GIII) or naked (D) according to morphological quality, packed in straws with maturation medium and sent to the laboratory on a carrier.They were cultured in a maturation medium for 22-24h. Following maturation, oocytes were submitted to fertilization between 18 and 22 h. The zygotes were transferred to a culture médium where remained for seven days. After the in vitro culture, the embryos were classified into morula (MO), initial blastocyst (BI), blastocyst (BL) and expanded blastocyst (BX) and packed in reeds containing culture medium, transported in a 5% CO2 atmosphere, 5% O2 at 36°C, for transfer in receivers properly synchronized. After 30 and 45 days of the innovation, the diagnosis of gestation was performed. The data were evaluated by the ShapiroWilk test, not attending normality criteria. The Mann-Whitney test was used to compare the means, considering a level of significance lower than 0.05. Bos indicus presented a greater oocyte recovery (n=2556), 15,9 oocytes/donors compared the Bos taurus (n=1903), 11,4 oocytes/donors (P=0,008). There was a difference in the morphological quality of COCs (689 and 444 in GI, P<0,0001; 681 and 509 in GIII, P=0,010), with zebu cattle superiority. There was no difference between breeds only for GII oocytes (1101 zebu cattle and 889 taurine cattle, P=0,110) and Doocytes (85 zebus cattle and 61 taurine cattle, P=0,311). Regarding the embryo production, was a difference in the percentages obtained from MO (0,44% zebu catlle and 6,42% taurine cattle, P=0,017), BL (14,18% zebu cattle and 3,74% taurine cattle, P<0,0001) and BX (81,43% zebu cattle and 75,13% taurine cattle, P<0,0001). There was no difference between breeds only for BI (3,96% zebu cattle and 14,71 taurine cattle, P=0,149). There was no difference between pregnancy rate (50,4% zebu cattle and 44,5 taurine cattle) (P>0,05). Bos indicus cows had a greater number of recovery oocytes and a higher number of viable oocytes compared to Bos taurus cows, as well as a higher production of viable embryos.