31 Overall Goat Cloning Efficiency Under Suboptimal Conditions — A 6-Year Experience
L. H. Aguiar A , C. E. Méndez-Calderón A , F. L. Ongaratto A C , R. Rossetto B , D. Rondina B , J. L. Rodrigues A , L. R. Bertolini C and M. Bertolini AA Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil;
B Ceará State University, Fortaleza, Ceará, Brazil;
C Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
Reproduction, Fertility and Development 30(1) 155-155 https://doi.org/10.1071/RDv30n1Ab31
Published: 4 December 2017
Abstract
Animal cloning involves a combination of several simple steps that need to be carried out at the highest efficacy to provide acceptable yet low overall cloning efficiency. Oocyte competence is key for proper somatic cell nucleus reprogramming, and technical elements must be refined to minimize interference in the overall outcome. The aim of this study was to compare the progress of a goat-cloning program over a 6-year period in which oocyte donors’ protocols and oocyte and embryo manipulation were continuously refined to cope with success under Brazilian semi-arid conditions. The cloning dataset was divided in 3 periods (P1, 2011-2012; P2, 2013-2014; P3, 2015-2016), using either in vivo- or in vitro-matured goat oocytes for cloning by nuclear transfer (NT) with different cell lines for subsequent transfer to synchronized recipients to produce transgenic liveborn kids. Over time, protocols for recovery of competent oocytes were adapted to existing conditions, also optimizing animal well being and nutritional status to attain better success. Data on total and viable oocytes, oocyte maturation, pregnancy, and cloning efficiency were analysed by the Chi-squared or t-test (P < 0.05). After 111 replicates, viable and matured oocyte rates were improved during the time, but mean number of total oocytes/donor were higher in the second period (25.4 ± 8.9 v. 18.5 ± 10.8 for P1 and 19.5 ± 6.1 for P3), whereas the mean of viable and matured oocytes were similar between P2 (19.4 ± 6.0 and 9.8 ± 4.6) and P3 (18.8 ± 7.0 and 9.6 ± 3.7), but higher than in P1 (12.8 ± 7.6 and 6.0 ± 4.1), respectively. Higher pregnancy rate was achieved in P1 and lower in P2, with both being similar to P3. However, the efficiency based on transferred embryos was similar between periods (Table 1). When compared with total oocytes, birth rate improved from the first to the last period (P1, 0.01%; P2, 0.02%; and P3, 0.09%). Cloning efficiency was measured by the number of transferred embryos compared with matured structures used for cloning, which showed an improvement over time (P1, 34.5%; P2, 43.9%; P3, 60.1%). A 5-fold enhancement was observed in the number of matured oocytes needed to produce a liveborn animal (P1, 2,779/1; P2, 1,892/1; P3, 545/1). Also, the number of donors (P1, 432; P2, 193.5; P3, 56.6) and recipients (P1, 114; P2, 57; P3, 27) needed to produce 1 animal was reduced by 7.6- and 4.2-fold between periods. In conclusion, complex and inefficient procedures such as cloning by NT require technical refinement and adjustments to existing conditions, including animal nutrition and welfare, and cumulative gain of expertise to attain successful results.
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