Delivery of cloned offspring: experience in Zebu cattle (Bos indicus)

Abstract

The production of a healthy cloned calf is dependent on a multitude of successful steps, including reprogramming mediated by the oocyte, the development of a functional placenta, adequate maternal-fetal interaction, the establishment of a physiological metabolic setting and the formation of a complete set of well-differentiated cells that will eventually result in well-characterised and fully competent tissues and organs. Although the efficiency of nuclear transfer has improved significantly since the first report of a somatic cell nuclear transfer-derived animal, there are many descriptions of anomalies concerning cloned calves leading to high perinatal morbidity and mortality. The present article discusses some our experience regarding perinatal and neonatal procedures for cloned Zebu cattle (B. indicus) that has led to improved survival rates in Nellore cloned calves following the application of such 'labour-intensive technology'.

Avaliação ultrassonográfica da involução das estruturas umbilicais extra e intracavitárias em bezerros sadios da raça Nelore concebidos naturalmente e produtos de fertilização in vitro

“…Em alguns destes estudos foi observado peso ao nascimento superior em animais concebidos por biotécnicas artificiais (Garry et al 1996, Kruip & den Daas 1997, Jacobsen et al 2000, Batchelder et al 2007, Meirelles et al 2010.…”

“…aliadas ao gigantismo, são bem caracterizadas nos bezerros clonados, assim como o maior tamanho dos vasos umbilicais e a maior incidência de doenças envolvendo essas estruturas (Garry et al 1996, Batchelder et al 2007, Miglino et al 2007, Meirelles et al 2010). Nos produtos de PIVE isso não está bem elucidado.…”

“…Como evidenciado na rotina prática, esses bezerros podem nascer com os vasos umbilicais mais calibrosos, os quais se atrofiam mais lentamente. No caso dos bezerros clonados já está bem caracterizado que nascem com tamanho e peso maiores, com vasos umbilicais de maior diâmetro e apresentam maior chance de desenvolverem doenças umbilicais (Garry et al 1996, Batchelder et al 2007, Miglino et al 2007, Meirelles et al 2010. A ocorrência da síndrome do bezerro grande (Large Offspring Syndrome) é comumente descrita em animais frutos de processos artificiais de fertilização e não somente nos bezerros clonados (Behboodi et al 1995, Kruip & den Daas 1997, Young et al 1998, Jacobsen et al 2000, Bertolini & Anderson 2002, Farin et al 2006.…”

Insights on bovine genetic engineering and cloning

“…More than 15 years have passed since the birth of the sheep Dolly, the first mammal cloned from the cells of an adult animal, however cloning is still an inefficient process. Of all cloned embryos transferred into recipient cows, usually less than 5% may develop in a healthy animal (Wilmut 2002, Cibelli et al 2007, Meirelles et al 2010. Although SCNT efficiency is still low, it is the technique that presents greater transgene expression stability in modified animals.…”

Challenges and perspectives to enhance cattle production via in vitro techniques: focus on epigenetics and cell-secreted vesicles

“…Gestational losses generally occur in the first trimester, until 90 days of gestation. Although its benefits, the in vitro production of cloned animals by NT is inefficient ( VAN WAGTENDONK-DE LEEUW et al, 1998;MEIRELLES et al, 2010); the birth rate is approximately 5% or less of transferred blastocysts. The competence of in vitro produced blastocysts is a critical stage of the NT process.…”