128 Features and developmental potential of oocytes collected from Nelore (Bos taurus indicus) calves at the early and late prepubertal phase
T. S. Kawamoto A , J. H. M. Viana B , T. P. Pontelo C , O. A. C. Faria D , A. A. G. Fidelis D , M. A. N. Dode B , L. N. Vargas A and R. A. Figueiredo BA Federal University of Uberlandia, Uberlandia, MG, Brazil
B EMBRAPA, Genetic Resources and Biotechnology, Brasilia, DF, Brazil
C Federal University of Lavras, Lavras, MG, Brazil
D University of Brasilia, Brasilia, DF, Brazil
Reproduction, Fertility and Development 34(2) 302-302 https://doi.org/10.1071/RDv34n2Ab128
Published: 7 December 2021
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
The use of calves as oocyte donors for in vitro embryo production (IVEP) is a strategy to shorten generation interval and to accelerate herds’ genetic gains. However, oocytes recovered from calves are less competent and generate fewer embryos than those obtained from adult cattle. This study evaluated the features and developmental capacity of oocytes obtained from Nelore calves at 2 to 5 and 8 to 11 months of age. Eight calves underwent oocyte retrieval every other 15 days, from 2 to 5 months of age by laparoscopic ovum pick-up (OPU) and from 8 to 11 months old by transvaginal OPU. Adult, multiparous cows were used as controls. The cumulus-oocyte complexes (COC) were used for IVEP. A subset of the oocytes was evaluated for morphology, diameter, and expression of genes related to oocyte transcriptional activity (HAT1, CREBBP, NCOA2, HDAC1, HDAC2, and HDAC3). Data were analysed by ANOVA or Kruskal–Wallis test, depending on normality (P < 0.05). Adult cattle produced more (P < 0.05) grade I (12.9% vs. 4.1% and 1.7%) and fewer grade III COC (30.1% vs. 44.5% and 49.0%, respectively) than 8- to 11-month and 2- to 5-month-old calves. Oocyte diameter in older calves was similar to that in cows but greater than that in younger calves (124.8 ± 8.5 μm and 126.0 ± 7.5 μm vs.121.3 ± 7.5 μm, respectively; P < 0.05). The expression of HDAC3 was up-regulated (P < 0.05) in cows compared to calves, and no difference was found for other genes. Blastocyst rates were similar between 8- to 11-month-old calves and adult controls (42.0% vs. 48.1%, respectively; P > 0.05), but lower in 2- to 5-month-old calves compared to their contemporaneous controls (31.0% vs. 71.6%, respectively; P < 0.05). When blastocyst rates were transformed to the proportion of the respective controls, they were lower in younger than in older calves (43.7% vs. 78.7%, respectively; P < 0.05). In summary, there is a progressive acquisition of oocyte developmental competence during the prepubertal period, and IVEP results in 8- to 11-month-old Nelore calves are similar to those of cows. These results should be considered when deciding whether is worth recovering oocytes from early prepubertal calves.
