127 Does selection for oocyte yield indirectly affect production traits in Gir cattle (Bos taurus indicus)?
L. Feres A , L. Siqueira B , M. Palhao A , L. Santos C , L. Pfeifer D and J. Viana EA Universidade Jose do Rosario Vellano, Alfenas, MG, Brazil
B Embrapa Gado de Leite, Juiz de Fora, MG, Brazil
C Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
D Embrapa Rondonia, Porto Velho, RO, Brazil
E Embrapa Recursos Genéticos e Biotecnologia, Brasilia, DF, Brazil
Reproduction, Fertility and Development 34(2) 301-302 https://doi.org/10.1071/RDv34n2Ab127
Published: 7 December 2021
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
In vitro embryo production (IVEP) has been broadly used in animal breeding programs worldwide, resulting in an increasing contribution of selected donors to the cattle population’s genetic status. However, the association between donor potential for IVEP and other important production traits is still not fully understood. The aim of the present study was to evaluate whether selection of donors, based on oocyte yield, could potentially impact the genetic progress of other production traits. To address that, we evaluated a database containing records of OPU-IVEP sessions performed on 658 Gir (Bos taurus indicus) donors from a dairy farm located at the state of Minas Gerais, Brazil. We considered only data from the very first OPU of each cow to avoid any bias due to the expected reduction in oocyte recovery observed when donors are repeatedly subjected to OPU. We analysed the numbers of total, viable, grade I oocytes, and the percentage of viable oocytes, as well as the number of embryos produced and blastocyst rates. Then, the genomic predicted transmitting ability for milk (GPTAm) and for age at first calving (GPTAafc) were determined for each donor using the GeneSeek Genomic Profiler (GGP) Bovine 50K microchip (Neogen Corp.). For data analysis, donors were first ranked into quartiles according to total oocyte yield, where the first quartile represents donors with the lowest oocyte numbers. All other endpoints were then compared among quartiles by ANOVA using the PROC GLM of SAS (SAS Institute Inc.). The associations between oocyte/embryo yield and GPTAm or GPTAafc were determined using the Pearson correlation method. Results are shown as mean ± s.e.m. or R (correlation coefficient) values. The average GPTAm was 235.2 ± 8.1 (ranging from −385 to 815) and GPTAafc was −5.7 ± 0.7 (ranging from −47 to 68). As expected, OPU-IVEP outcomes differed among quartiles (total oocytes: 11.4 ± 0.3a, 22.4 ± 0.2b, 33.2 ± 0.3c, and 54.8 ± 1.2d; viable oocytes: 8.2 ± 0.3a, 17.3 ± 0.3b, 26.0 ± 0.4c, and 44.1 ± 1.2d; and embryos produced: 1.6 ± 0.1a, 2.0 ± 0.2a, 3.3 ± 0.3b, and 4.7 ± 0.5c for quartiles I, II, III, and IV, respectively; P < 0.0001). Cows within the last quartile produced 2.9-fold more embryos (37.2% of total) than those within the first quartile. Nevertheless, there was no difference in GPTAm (P = 0.2721) or GPTAafc (P = 0.2178) among quartiles. There was also no correlation between GPTAafc and total oocytes (R = 0.05, P = 0.17); viable oocytes (R = 0.01, P = 0.87); embryos produced (R = −0.01, P = 0.91); or embryo rate (R = 0.03, P = 0.43). In contrast, a low but significant correlation between GPTAm and the number of total and viable oocytes recovered (R = 0.09, P = 0.02, and R = 0.12, P = 0.002, respectively) was observed, even though GPTAm did not affect embryo production nor blastocyst rate (R = 0.07, P = 0.08, and R = −0.06, P = 0.13, respectively). In summary, our results suggest that intensive use of IVEP in Gir donors may result in a low but positive selection for GPTAm over time.
This research was supported by Fazendas do Basa, Fapemig CVZ APQ 03430-17.
