Reproduction in Domestic Animals

Reprod Dom Anim 43 (Suppl. 2), 1–7 (2008); doi: 10.1111/j.1439-0531.2008.01136.xISSN 0936-6768The Manipulation of Gametes and Embryos in Farm AnimalsC Galli 1,2 and G Lazzari 11 Laboratorio di Tecnologie della Riproduzione, Istituto Sperimentale Italiano Lazzaro Spallanzani, CIZ srl, Cremona, Italy; 2 Dip. ClinicoVeterinario, Universita` di Bologna, Bologna, ItalyContentsThis paper summarizes the major advances in farm animalassisted reproduction in the last 20 years with particularattention to the contributions of the authors. A main emphasisis on the biology of the oocyte, including a description ofmethods for isolation of developing follicles and culture of thecorresponding oocytes. Milestones that have led to optimizationof procedures for maturation of fully grown oocytes,fertilization, intracytoplasmic sperm injection and embryoculture in sheep, cattle, pigs and horses are described. Thecurrent status of nuclear transfer, cloning and embryonic stemcell generation and culture is also summarized for all majorfarm animal species. It is concluded that the manipulation ofearly development in farm animals is of crucial importance foragricultural purposes and that reproductive biotechnologies infarm animals are expected to play an increasing role in the nextdecades due to the growing demand for agricultural productsfrom the emerging economies worldwide. In the biomedicalfield large animals represent increasingly important researchmodels especially in the stem cell field for creating geneticallymodified animals for specific purposes. Finally, the successfultranslation of large animal research in the applied contextrequires solid science, long-term resource commitment frominvolved institutions, and vision, dedication and entrepreneurialskills from the scientists involved.IntroductionDespite the many scientific advances that have characterizedreproduction research, the science of reproductionretains an aura of wonder. This feeling is captured inHarvey’s phrase: ‘ex ovo omnia’ and this fundamentaltruth explains the central role that reproduction has inbiology of all life including our own. In livestockbreeding, as well as for companion animals and wildlifeconservation, reproduction and selection allow maintenanceand propagation of species and breeds. Mostimportantly, farm animal reproduction is a centralphenomenon required for genetic selection to improveproductive ⁄ reproductive traits in the next generation.Genomics, proteomics and marker-assisted selectionwould all be limited technologies if not exploited throughreproduction. The development of assisted reproductiontechniques, as advanced tools for animal breeding, hasbeing instrumental for the acquisition of in-depth knowledgeof the molecular mechanisms of the reproductionprocesses, for studying gametes and embryos and forallowing the manipulation of early development in farmanimals. The strong driving force behind the advancementof reproductive technologies has been the need foragricultural and, more recently, biomedical applications.In many instances, the technical achievements havesurpassed the full understanding of the underlyingbiological mechanisms for those achievements.In this paper, we will discuss the in vitro reproductivetechnologies that have had the greatest impact onanimal breeding and highlight our contributions to theirdevelopment. For this reason, it was not the aim of thepaper to make an extensive review of the publishedliterature but rather to mention the work and publicationsthat have directly inspired our work. We apologizein advance for those citations that are not included.At the beginning of our career in science, in the mid-1980s, the only embryo technology that was applied inpractice was superovulation and embryo transfer [multipleovulation embryo transfer (MOET)]. At that time,soon became apparent that the MOET technique hadmany limits and other ways could be developed forproducing embryos required by the cattle industry. Aseminal paper published by Staigmiller and Moor (1984)drew our attention, as it demonstrated that immatureoocytes, after in vitro maturation (IVM), could beconverted into viable embryos and offspring at a level ofefficiency that was remarkably high. Our interest wasparticularly attracted to the female germ line. On theone hand, we dreamed about the possibility of exploitingthe large pool of growing oocytes in the ovaries and,on the other hand, we aimed at rescuing those fullygrown oocytes present in medium to large size folliclesthat exist throughout the reproductive lifetime of femalecattle. The aim was to overcome the physiologicallimitation of conventional breeding, especially in themonotocycous Bos taurus, and make a better use offemale gametes that were otherwise destined to wastageby atresia. In this way, the genetic impact of females ofsuperior genotype and performance on a given populationcould be greatly amplified. Indeed the oocyte is themost interesting cell in biology and may play the mostcrucial role in successful breeding. A significant proportionof successful embryo development can be relatedback to the oocyte (Staigmiller and Moor 1984) and theproduction of large number of good quality oocytesusing in vitro techniques opened a new era in embryotechnologies for farm animals.In this paper, we will review our work of the last20 years. Efforts started with a specific interest in theoocyte and evolved into building novel approaches toembryo-related biotechnologies ranging from control ofmeiosis, in vitro fertilization (IVF), embryo culture,nuclear transfer, stem cells and genetic modification oflarge domestic animals. We always worked in anultrashort feedback loop between fundamental researchand technology application, in close contact with theend users of the technologies that we were working on.Such contacts have served as a strong reminder thatany new technology has to have application. In ourÓ 2008 The Authors. Journal compilation Ó 2008 Blackwell Verlag