68 REPRODUCTIVE PERFORMANCE OF CLONED BULLS
R.T. Tecirlioglu A D , M.A. Cooney A D , N.A. Korfiatis A D , R. Hodgson B D , M. Williamson C , S. Downie B D , D.B. Galloway A B , M.K. Holland A D and A.J. French A DA Monash Institute of Reproduction and Development, Monash University, Clayton, Victoria 3168, Australia
B Genetics Australia Co-operative Limited, Bacchus Marsh, Victoria 3340, Australia
C The Gribbles Group, Clayton, Victoria 3168, Australia
D Cooperative Research Centre for Innovative Dairy Products, Melbourne, Victoria 3000, Australia. Email: tayfur.tecirlioglu@med.monash.edu.au
Reproduction, Fertility and Development 17(2) 184-184 https://doi.org/10.1071/RDv17n2Ab68
Submitted: 1 August 2004 Accepted: 1 October 2004 Published: 1 January 2005
Abstract
The generation of cloned animals by somatic cell nuclear transfer has been reported in a number of countries worldwide. However, progress has been impeded by the extremely low efficiency of cloning and health of some of the cloned animals. Surprisingly, little is known of the reproductive performance of viable clones when compared to the original cell donor, given that a major motivation of cloning is dissemination of superior genotypes. The aim of this study was to compare semen collected from three cloned bulls (Clones A1, B1, and B2) to that of the original donor bulls (Donors A and B). Parameters examined included ejaculate volume, sperm concentration and the motility characteristics of frozen/thawed semen using computed-assisted semen analysis (Hamilton Thorne Biosciences, Inc., Beverly, MA, USA). The fertilization ability of each semen sample was examined using in vitro matured oocytes derived from abattoir-source ovaries. Frozen/thawed semen samples from donor and cloned bulls were prepared on a Percoll gradient and diluted with fertilization medium to a concentration of 1 million sperm/mL prior to fertilization (IVF). The number of blastocysts and total cell counts were analyzed on Day 7 of culture. Finally, in vitro-fertilized blastocysts (Day 7) were transfer to synchronized recipients (n = 49) to examine in vivo development. Proportional data for the in vitro development of embryos and subsequent pregnancy rates were analyzed by chi-square test, and embryo cell numbers were analyzed using Student's t-test. Progressive motility percentage between donor and cloned bull did not differ: Donor A (62.25 ± 3.89, n = 12); Donor B (66.69 ± 4.47, n = 13); Clone A1 (71.37 ± 8.57, n = 8); Clone B1 (73.75 ± 2.42, n = 12); Clone B2 (72.41 ± 3.26, n = 12). No obvious differences in kinetic motility parameters were evident between cloned and non-cloned donor animals. However, blastocyst rates were significantly higher in cloned bulls (Clone A1: 30.9%, 81/262; Clone B1: 34.4%, 98/285; and Clone B2: 42.9%, 120/280) compared to donor bulls (Donor A: 20.7%, 54/261; Donor B: 20.9%, 76/364). Total embryo cell numbers did not differ significantly between donor bulls (Donor A: 138.3 ± 5.3, n = 39; Donor B: 133.2 ± 5.2, n = 47) and cloned bulls (Clone A1; 126.3 ± 4.4, n = 45; Clone B1: 134.4 ± 7.1, n = 26; and Cloned B2: 140.1 ± 3.9, n = 46). Initial pregnancy rates on Day 30 were also not different between Donor A (42.3%, 11/26) and Clone A1 (47.8%, 11/23). Preliminary observations from the small data set on postpubertal cloned bulls indicate that semen production, semen morphology, and reproductive performance (in vitro and in vivo) were similar in terms of semen characteristics and reproductive performances when compared to their original donor bulls.
