bluuebunny/crossref_metadata_2025_split huggingface dataset:
Endocrine Disruptors and Other Food‐contaminating Environmental Pollutants as Risk Factors in Animal Reproduction
Authors: Rhind SM 
Published: July 2008

ContentsPollutants of many chemical classes, derived primarily from anthropogenic activities, are ubiquitous in the environment, persistent, biologically available and can exert adverse effects on the reproductive and other, indirectly related, physiological systems. Food is generally considered to be the major route of animal exposure in vertebrate species but the relative contributions of other routes of exposure such as through lungs, gills or skin are not well studied and may be of importance for certain animal groups, depending on their immediate environment. Animals are particularly sensitive to exposure during developmental stages but the pattern of exposure to chemicals is likely to be different to that of adults. Quantification of the risk posed by the ingestion of pollutants in food is complex and depends on many factors including species, diet composition, duration of exposure to the food, efficiency of pollutant absorption, subsequent metabolism, sensitivity of target organs and stage of development. While the effects of high doses of single chemicals are proven, dietary exposure to pollutants generally involves prolonged, low‐level exposure to a large number of compounds, each of which has different chemical characteristics, exerts different biological effects and is present at varying concentrations. Thus, while exposure to pollutants through feed is undoubtedly a significant risk factor for many species and may be the most important one for many terrestrial vertebrates, other routes of exposure may be more important in other groups.
Long Chain Fatty Acids of Diet as Factors Influencing Reproduction in Cattle
Authors: Santos JEP , Bilby TR , Thatcher WW , Staples CR , Silvestre FT 
Published: July 2008

ContentsCattle are fed moderate amounts of long chain fatty acids (FA) with the objective to enhance lactation and growth; however, recent interest on lipid feeding to cows has focused on reproduction, immunity and health. Increasing the caloric density of the ration by fat feeding has generally improved measures of cow reproduction, but when milk yield and body weight losses were increased by fat supplementation, positive effects on reproduction were not always observed. Feeding fat has influenced reproduction by altering the size of the dominant follicle, hastening the interval to first postpartum ovulation in beef cows, increasing progesterone concentrations during the luteal phase of the oestrous cycle, modulating uterine prostaglandin (PG) synthesis, and improving oocyte and embryo quality and developmental competence. Some of these effects were altered by the type of FA fed. The polyunsaturated FA of the n‐6 and n‐3 families seem to have the most remarkable effects on reproductive responses of cattle, but it is not completely clear whether these effects are mediated only by them or by other potential intermediates produced during rumen biohydrogenation. Generally, feeding fat sources rich in n‐6 FA during late gestation and early lactation enhanced follicle growth, uterine PG secretion, embryo quality and pregnancy in cows. Similarly, feeding n‐3 FA during lactation suppressed uterine PG release, and improved embryo quality and maintenance of pregnancy. Future research ought to focus on methods to improve the delivery of specific FA and adequately powered studies should be designed to critically evaluate their effects on establishment and maintenance of pregnancy in cattle.
Reproductive Biotechnology and Gene Mapping: Tools for Conserving Rare Breeds of Livestock
Authors: Long JA 
Published: July 2008

ContentsToday’s livestock diversity originated from the wild ancestor species and was subsequently shaped through the processes of mutation, genetic drift, and natural and human selection. Only a subset of the diversity present in the ancestral species survives in the domestic counterparts. A 2007 report released by UN Food and Agriculture Organization ‘The State of the World’s Animal Genetic Resources’, compiled from surveys conducted in 169 countries, found that nearly 70% of the world’s remaining livestock breeds live in developing countries. The UN report was presented to more than 300 policy makers, scientists, breeders, and livestock keepers at the First International Technical Conference on Animal Genetic Resources, held in September 2007 in Interlaken, Switzerland. The conference aims were to adopt a global plan of action for conserving animal genetic resources as its main outcome. In this paper, the current and potential contributions of reproductive and molecular biotechnology are considered as tools of conserving rare breeds of livestock.
Genetic Improvement of Dairy Cow Reproductive Performance
Authors: Berglund B 
Published: July 2008

ContentsThe welfare of cow along with profitability in production are important issues in sustainable animal breeding programmes. Along with an intense/intensive selection for increased milk yield, reproductive performance has declined in many countries, in part due to an unfavourable genetic relationship. The largely unchanged genetic trend in female fertility and calving traits for Scandinavian Red breeds shows that it is possible to avoid deterioration in these traits if they are properly considered in the breeding programme. Today’s breeding is international with a global selection and extensive use of the best bulls. The Nordic countries have traditionally recorded and performed genetic evaluation for a broad range of functional traits including reproduction. In recent years many other countries have also implemented genetic evaluation for these traits. Thus, the relative emphasis of dairy cattle breeding objectives has gradually shifted from production to functional traits such as reproduction. Improved ways of recording traits, e.g. physiological measures, early indicator traits, assisted reproductive techniques and increased knowledge of genes and their regulation may improve the genetic selection strategies and have large impact on present and future genetic evaluation programmes. Extensive data bases with phenotypic recordings of traits for individuals and their pedigree are a prerequisite. Quantitative trait loci have been associated to the reproductive complex. Most important traits, including reproduction traits are regulated by a multitude of genes and environmental factors in a complex relationship, however. Genomic selection might therefore be important in future breeding programmes. Information on single nucleotide polymorphism has already been introduced in the selection programmes of some countries.
Nutrient Prioritization in Dairy Cows Early Postpartum: Mismatch Between Metabolism and Fertility?
Authors: Leroy JLMR , Vanholder T , Van Knegsel ATM , Garcia‐Ispierto I , Bols PEJ 
Published: July 2008

ContentsFor several decades, researchers worldwide report a decrease in fertility in high‐yielding dairy cows, most probably based on conflicting metabolic and reproductive needs. The dairy herd manager’s success at improving milk production has been accompanied by a negative trend for the most visible reproductive parameters such as calving intervals, number of days open and number of inseminations needed per pregnancy. In parallel, many research groups studied the metabolic and endocrine factors that influence follicular growth and the developmental competence of oocytes and embryos. In the past, herd managers and reproductive biologists each tried to tackle the same problems with limited consultation. More recently, the situation has improved significantly and theriogenologists, nutritionists and veterinarians now conduct research in multidisciplinary teams. This review paper starts in a general way by discussing nutrient prioritization towards the udder to guarantee milk production and by describing interactions between the somatotropic and gonadotropic axis. It then focuses on the consequences of the negative energy balance on follicular growth and environment, oocyte and embryo quality, not only by summarizing the currently accepted hypotheses but also based on clear scientific evidence at the follicular level. All this, with one question in mind: is there a mismatch between metabolism and fertility and what can the dairy manager learn from research to tackle the problem of reduced fertility?
Corpus Luteum–Endometrium–Embryo Interactions in the Dairy Cow: Underlying Mechanisms and Clinical Relevance
Authors: Robinson RS , Hammond AJ , Wathes DC , Hunter MG , Mann GE 
Published: July 2008

ContentsConception rates of dairy cows are currently declining at an estimated 1% every year. Approximately, 35% of embryos fail to prevent luteolysis during the first three weeks of gestation. Interactions between the corpus luteum, endometrium and embryo are critical to the successful establishment of pregnancy and inadequacies will result in the mortality of the embryo. For example, as little as a one day delay in the post‐ovulatory rise of progesterone has serious consequences for embryo development and survival. Recently, we found that LH support, degree of vascularization and luteal cell steroidogenic capacity were not the major factors responsible for this luteal inadequacy, but are nevertheless essential for luteal development and function. Progesterone acting on its receptor in the endometrium stimulates the production of endometrial secretions on which the free‐living embryo is dependent. However, their exact composition and effects of inadequate progesterone remains to be determined. The embryo is recognized through its secretion of interferon tau (IFNT), which suppresses luteolytic pulses of prostaglandin F2α. In the cow, it is most likely that IFNT inhibits oxytocin receptor up‐regulation directly and does not require the prior inhibition of oestrogen receptor α (ESR1). Unravelling the precise luteal‐endometrium and embryo interactions is essential for us to understand pregnancy establishment and development of strategies to reverse the declining fertility of dairy cows.
The Importance of Interactions Among Nutrition, Seasonality and Socio‐sexual Factors in the Development of Hormone‐free Methods for Controlling Fertility
Authors: Scaramuzzi RJ , Martin GB 
Published: July 2008

ContentsAround the world, consumers are demanding animal products that are produced to agreed standards for human health, environmental management and animal welfare. This has led to the development in Australia of the concept of ‘clean, green and ethical’ (CGE) animal production based on the manipulation of nutrition (‘focus feeding’) and the application of phenomena, such as the ‘male effect’, to provide ‘natural’ methods for managing small ruminant production systems. With respect to the management of fertility, CGE involves utilization of the inherited responses of animals to environmental factors to manipulate their reproductive processes. The successful development and implementation of this new generation of management tools depends on a thorough yet holistic understanding of the interactions among environmental factors and the ways these interactions affect reproductive physiology and behaviour of the animal. For sheep and goats, a central aspect of CGE management is the way in which ovarian function is affected by three major factors (nutrition, photoperiod and socio‐sexual signals) and by interactions among them. Nutrition can exert two profound yet contrasting types of effect on ovarian activity: (i) the complete inhibition of reproduction by undernutrition through the hypothalamic mechanism that controls ovulation and (ii) the enhancement of fecundity by nutritional supplementation, through a direct ovarian mechanism, in females that are already ovulating. A similarly profound control over ovarian function in female sheep and goats is exerted by the well‐known endocrine responses to photoperiod (seasonality) and to male socio‐sexual signals. The ‘male effect’ already has a long history as a valuable technique for inducing a synchronized fertile ovulation during seasonal and post‐partum anoestrus in sheep and goats. Importantly, experimentation has shown that these three major environmental factors interact, synergistically and antagonistically, but the precise nature of these interactions and their significance to reproductive outcomes are not well understood. Most research to date has been with small ruminants but CGE principles can be applied to any species in a managed environment. For example, a male effect has been reported for lactating cattle and, in the horse, the pattern of seasonality of oestrus can be altered by nutrition. Well‐fed mares have a longer breeding season and some animals become non‐seasonal. Similar observations have been reported for sheep and goats. By working towards a holistic perspective of the physiology, nutrition, genetics and behaviour of our animals, we will be able to formulate ways to manipulate the animals’ environment that will improve management, productivity and profitability and, simultaneously, promote a CGE industry.
Developmental Capabilities of Embryos Produced In Vitro from Prepubertal Lamb Oocytes
Authors: Morton KM 
Published: July 2008

ContentsBreeding from prepubertal females, known as juvenile in vitro embryo transfer (JIVET), reduces the generation interval and increases the rate of genetic gain in animal breeding programs. While the birth of the first lambs from prepubertal ewes occurred nearly 30 years ago; and there is considerable interest in the commercialization of this technology, its efficiency remains too low. The advent of in vitro production (IVP) of embryo resulted in the more widespread use of JIVET. Morphologic and metabolic differences coupled with reduced in vitro and in vivo development of oocytes derived from prepubertal animals have been reported. Research has been undertaken to optimize donor selection and hormone stimulation methods in an attempt to reduce the variability and increase the proportion of donors responding to hormone stimulation and increase oocyte developmental competence. Yet, this variation persists and the development of oocytes and embryos from prepubertal animals remains reduced when compared with adults. Recent improvements to JIVET, resulting from a modified hormone stimulation regime, have eliminated the failure of donors to respond to hormone stimulation, and increased both the number and developmental competence of oocytes harvested from very young prepubertal lambs. This increased efficiency has facilitated the incorporation of other reproductive technologies such as sperm sexing with JIVET, resulting in the birth of lambs of a pre‐determined sex from prepubertal lambs. Increased rates of genetic gain in sheep breeding programs can be achieved by combining sexed sperm with oocytes obtained from lambs as young as 3–4 weeks of age. Continued increases in the efficiency of JIVET resulting from further improvements to hormone stimulation regimes and an increased understanding of the differences between oocytes from adult and prepubertal animals will result in the commercialization of this technology.
The Ethics and Role of AI with Fresh and Frozen Semen in Dogs
Authors: England GCW , Millar KM 
Published: July 2008

ContentsThe use of artificial insemination (AI) with fresh semen has resulted in many benefits for the management of dog breeding, but there are disadvantages that can sometimes be overlooked. Furthermore, poorer quality semen arising as a result of cryopreservation necessitates uterine insemination, which raises the potential for surgical insemination. A number of significant ethical concerns have been raised by key stakeholders (such as The Kennel Club and the Royal College of Veterinary Surgeons) about AI per se, but particularly about the use of surgical insemination. This paper discusses the technological development of AI and explores a number of the ethical issues raised by its application to dog breeding. An Ethical Matrix method is used to map the potential ethical issues for key interest groups, namely dogs, breeders, owners, veterinarians and wider society. There are national variations in the way in which institutions have evaluated potential ethical impacts, and this is reflected in the different regulatory frameworks governing the use of AI in dogs. In order to facilitate decision‐making and reduce some of the ethical risks associated with this technology, the veterinary research community could take several proactive steps including: (i) clarifying clinical decision‐making processes, (ii) enhancing informed choice among clients and (iii) increasing the knowledge‐base of potential impacts of AI.
Controlling Animal Populations Using Anti‐Fertility Vaccines
Authors: Fayrer‐Hosken R 
Published: July 2008

ContentsThe goal for fertility control of animal populations is the development of a safe, economical and effective contraceptive. One offshoot of the development of this technology is the acquisition of multiple therapeutic strategies for diseases, such as immunotherapy probes for cancer. In the long run, successful population control requires multifactorial strategies. One component of population control is immunocontraception. Development of effective antigens for immunocontraceptive vaccines has been remarkable and has greatly advanced our understanding of the molecular mechanisms of fertilization. The chasm between the discovery of an antigen in the laboratory, to the implementation of an effective field program, is immense. The zona pellucida (ZP) immunocontraceptive that has been most extensively evaluated as a fertility vaccine antigen and the porcine ZP has received particular attention. The long‐term goal of population control would be the use of a synthetic vaccine, e.g. the ZP, tailored to a target species. In the future, if populations’ levels are to be controlled by fertility vaccines, we should consider that the vaccinated animals could receive other health protective agents at the same time. For example, if a species were immunocontracepted, then they could be simultaneously vaccinated against habitat diseases such as rabies (Plumb et al., Rev Sci Tech, 26, 2007, 229).
Recent Progress in Embryonic Stem Cell Research and Its Application in Domestic Species
Authors: Brevini TAL , Antonini S , Pennarossa G , Gandolfi F 
Published: July 2008

ContentsMany reports described cell lines derived in domestic species, which presented several important features typical of embryonic stem cells (ESCs). Such features unfortunately did not include the capacity to generate germ‐line chimeras, therefore limiting the possibility to use these cells as tools for the genetic manipulation. However, farm animal ESCs may still be useful for the generation of transgenic animals as usually have a self‐renewal capacity more prolonged than normal primary cultures thus increasing the possibility to transform and select cells to be used as nucleus donors in cloning procedures. Farm animal ESCs may also be an excellent experimental model in pre‐clinical trials, assessing the feasibility of cell therapy because of the close morphological and physiological resemblance to humans of species like the pig. However, the persistent lack of standard methods for the derivation, maintenance and characterization of ESCs in domestic species stimulated the search for alternatives. Embryonic germ cells may represent such an alternative. Indeed, these cells showed a higher plasticity than ESCs as contributed to embryonic development forming chimeric newborns but, as for ESCs, standardization is still far away and efficiency is very low. Recent results indicated spermatogonial stem cells as possible tools for germ‐line genetic modifications with some proof of principle results already achieved. But, a real break through could arrive from the multipotent germ‐line stem cells, virtually equivalent to ESC, derived from newborn and adult mouse testis.
Reproduction in Domestic Buffalo
Authors: Perera BMAO 
Published: July 2008

ContentsThe domestic buffalo is an indispensable livestock resource to millions of smallholder farmers in developing countries, particularly in Asia. Although its reproductive biology is basically similar to that of cattle, there are important differences and unique characteristics that need to be considered in order to apply modern reproductive technologies to improve its productivity. Under most smallholder production systems, the reproductive efficiency of buffalo is compromised by factors related to climate, management, nutrition and diseases. However, when managed and fed properly, buffalo can have good fertility and provide milk, calves and draught power over a long productive life. The basic technical problems associated with artificial insemination in buffalo were largely overcome two decades ago, but the technology has not had the expected impact in some developing countries, because largely of infrastructural and logistic problems. Approaches involving the use of hormones for treating anoestrus and for synchronizing oestrus have had varying rates of success, depending on the protocols used and the incidence of underlying problems that cause infertility. Embryo technologies such as multiple ovulation embryo transfer, in vitro embryo production, cryopreservation and cloning are being intensively studied but have had far lower success rates than in cattle. Improving the productivity of buffalo requires an understanding of their potential and limitations under each farming system, development of simple intervention strategies to ameliorate deficiencies in management, nutrition and healthcare, followed by judicious application of reproductive technologies that are sustainable with the resources available to buffalo farmers.
Mother–Offspring Interactions in Zebu Cattle
Authors: Paranhos da Costa MJR , Schmidek A , Toledo LM 
Published: July 2008

ContentsThe knowledge of the interaction between mother and offspring might contribute to enhance the welfare of the offspring and to improve the reproductive efficiency of the cow. However, there is still little information available about such interaction in some cattle breeds. A series of observational studies were set up, addressing the mother–offspring relationships of Nelore, Guzerat and Gyr cattle breeds. Firstly, the behaviour of cows and calves around the time of parturition was described, and then, the underlying factors that affect the calves’ survival and development were studied. Special attention was given to the failure or delay in the first suckling. The results together are indicative of genetic variability for some studied variables, indicating the possibility of selection for calf vigour (using latency to stand up and latency to suckle as its indicators) and maternal ability (using percentage of time in contact with the calves), in spite of the estimates of heritability were low and presented high standard deviation for all variables. The individual variability in their suckling behaviour and the efficiency in first suckling cannot be explained by a single isolated underlying factor. By now, there are some results available, although there are many questions without answers. The field is still open for the development of future research.