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- Volume 1, 2013
Annual Review of Animal Biosciences - Volume 1, 2013
Volume 1, 2013
- Preface
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After 65 Years, Research Is Still Fun
Vol. 1 (2013), pp. 1–20More LessIn 1946, at the end of World War II, I entered graduate school at Cornell University, where I remained for 44 years. During that time, my laboratory produced more than 300 publications in the field of reproductive biology, including studies on nutrition and reproduction, the role of the hypothalamus in pituitary gonadotropin release, corpus luteum formation and function, hormone assays, and estrous cycle synchronization. At age seventy, I retired from Cornell and accepted the Gordon Cain Endowed Professorship at Louisiana State University, where I continued my work on the bovine corpus luteum and added research on the collection, maturation, in vitro fertilization, and culture of bovine oocytes. In 1994, I moved to the Pennington Biomedical Research Center and soon thereafter started the research that led to development of the lytic peptide–gonadotropin conjugates, which target and destroy cancer cell membranes. I am continuing my work on the development of targeted cancer cell drugs and, yes, research is still fun!
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Cross Talk Between Animal and Human Influenza Viruses
Vol. 1 (2013), pp. 21–42More LessAlthough outbreaks of highly pathogenic avian influenza in wild and domestic birds have been posing the threat of a new influenza pandemic for the past decade, the first pandemic of the twenty-first century came from swine viruses. This fact emphasizes the complexity of influenza viral ecology and the difficulty of predicting influenza viral dynamics. Complete control of influenza viruses seems impossible. However, we must minimize the impact of animal and human influenza outbreaks by learning lessons from past experiences and recognizing the current status. Here, we review the most recent influenza virology data in the veterinary field, including aspects of zoonotic agents and recent studies that assess the pandemic potential of H5N1 highly pathogenic avian influenza viruses.
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Porcine Circovirus Type 2 (PCV2): Pathogenesis and Interaction with the Immune System
Vol. 1 (2013), pp. 43–64More LessPorcine circovirus type 2 (PCV2) is the primary causative agent of porcine circovirus–associated disease (PCVAD). The virus preferentially targets the lymphoid tissues, which leads to lymphoid depletion and immunosuppression in pigs. The disease is exacerbated by immunostimulation or concurrent infections with other pathogens. PCV2 resides in certain immune cells, such as macrophage and dendritic cells, and modulates their functions. Upregulation of IL-10 and proinflammatory cytokines in infected pigs may contribute to pathogenesis. Pig genetics influence host susceptibility to PCV2, but the viral genetic determinants for virulence remain unknown. PCV2 DNA and proteins interact with various cellular genes that control immune responses to regulate virus replication and pathogenesis. Both neutralizing antibodies and cell-mediated immunity are important immunological correlates of protection. Despite the availability of effective vaccines, variant strains of PCV2 continue to emerge. Although tremendous progress has been made toward understanding PCV2 pathogenesis and immune interactions, many important questions remain.
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Evolution of B Cell Immunity
Vol. 1 (2013), pp. 65–97More LessTwo types of adaptive immune strategies are known to have evolved in vertebrates: the VLR-based system, which is present in jawless organisms and is mediated by VLRA and VLRB lymphocytes, and the BCR/TCR-based system, which is present in jawed species and is provided by B and T cell receptors expressed on B and T cells, respectively. Here we summarize features of B cells and their predecessors in the different animal phyla, focusing the review on B cells from jawed vertebrates. We point out the critical role of nonclassical species and comparative immunology studies in the understanding of B cell immunity. Because nonclassical models include species relevant to veterinary medicine, basic science research performed in these animals contributes to the knowledge required for the development of more efficacious vaccines against emerging pathogens.
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Comparative Biology of γδ T Cell Function in Humans, Mice, and Domestic Animals
Vol. 1 (2013), pp. 99–124More Lessγδ T cells are a functionally heterogeneous population and contribute to many early immune responses. The majority of their activity is described in humans and mice, but the immune systems of all jawed vertebrates include the γδ T cell lineage. Although some aspects of γδ T cells vary between species, critical roles in early immune responses are often conserved. Common features of γδ T cells include innate receptor expression, antigen presentation, cytotoxicity, and cytokine production. Herein we compare studies describing these conserved γδ T cell functions and other, potentially unique, functions. γδ T cells are well documented for their potential immunotherapeutic properties; however, these proposed therapies are often focused on human diseases and the mouse models thereof. This review consolidates some of these studies with those in other animals to provide a consensus for the current understanding of γδ T cell function across species.
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Genetics of Pigmentation in Dogs and Cats
Vol. 1 (2013), pp. 125–156More LessColor variation in companion animals has long been of interest to the breeding and scientific communities. Simple traits, like black versus brown or yellow versus black, have helped to explain principles of transmission genetics and continue to serve as models for studying gene action and interaction. We present a molecular genetic review of pigmentary variation in dogs and cats using a nomenclature and logical framework established by early leaders in the field. For most loci in which molecular variants have been identified (nine in dogs and seven in cats), homologous mutations exist in laboratory mice and/or humans. Exceptions include the K locus in dogs and the Tabby locus in cats, which give rise to alternating stripes or marks of different color, and which illustrate the continued potential of coat color genetics to provide insight into areas that transcend pigment cell biology.
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Cats: A Gold Mine for Ophthalmology
Vol. 1 (2013), pp. 157–177More LessOver 200 hereditary diseases have been identified and reported in the cat, several of which affect the eye, with homology to human hereditary disease. Compared with traditional murine models, the cat demonstrates more features in common with humans, including many anatomic and physiologic similarities, longer life span, increased size, and a genetically more heterogeneous background. The development of genomic resources in the cat has facilitated mapping and further characterization of feline models. During recent years, the wealth of knowledge in feline ophthalmology and neurophysiology has been extended to include new diseases of significant interest for comparative ophthalmology. This makes the cat an extremely valuable animal species to utilize for further research into disease processes affecting both cats and humans. This is especially true in the advancement and study of new treatment regimens and for extended therapeutic trials. Groups of feline eye diseases reviewed in the following are lysosomal storage disorders, congenital glaucoma, and neuroretinal degenerations. Each has important implications for human ophthalmic research.
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Comparative Aspects of Mammary Gland Development and Homeostasis
Vol. 1 (2013), pp. 179–202More LessMammary glands are crucial to the reproductive strategy of mammals, and the milk of domesticated ruminants serves as an important source of nutrients for the human population. The majority of mammary gland development occurs postnatally, and the mammary gland undergoes cyclical periods of growth, differentiation, lactation, and regression that are coordinated to provide nutrients for offspring or are driven by strategies to manage reproduction and milk production of domesticated species. Growth and maintenance of the mammary epithelium depends on the function of mammary stem cells and progenitor cells. In this review, we provide an overview of postnatal mammary gland development, cyclical phases of mammary gland regression (regression during lactation and between successive lactations), and mammary stem cells and progenitor cells. Where possible, these processes are related to animal production and compared across species, particularly bovine, porcine, murine, and human.
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Genetically Engineered Pig Models for Human Diseases
Vol. 1 (2013), pp. 203–219More LessAlthough pigs are used widely as models of human disease, their utility as models has been enhanced by genetic engineering. Initially, transgenes were added randomly to the genome, but with the application of homologous recombination, zinc finger nucleases, and transcription activator-like effector nuclease (TALEN) technologies, now most any genetic change that can be envisioned can be completed. To date these genetic modifications have resulted in animals that have the potential to provide new insights into human diseases for which a good animal model did not exist previously. These new animal models should provide the preclinical data for treatments that are developed for diseases such as Alzheimer’s disease, cystic fibrosis, retinitis pigmentosa, spinal muscular atrophy, diabetes, and organ failure. These new models will help to uncover aspects and treatments of these diseases that were otherwise unattainable. The focus of this review is to describe genetically engineered pigs that have resulted in models of human diseases.
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Accelerating Improvement of Livestock with Genomic Selection
Vol. 1 (2013), pp. 221–237More LessThree recent breakthroughs have resulted in the current widespread use of DNA information: the genomic selection (GS) methodology, which is a form of marker-assisted selection on a genome-wide scale, and the discovery of large numbers of single-nucleotide markers and cost effective methods to genotype them. GS estimates the effect of thousands of DNA markers simultaneously. Nonlinear estimation methods yield higher accuracy, especially for traits with major genes. The marker effects are estimated in a genotyped and phenotyped training population and are used for the estimation of breeding values of selection candidates by combining their genotypes with the estimated marker effects. The benefits of GS are greatest when selection is for traits that are not themselves recorded on the selection candidates before they can be selected. In the future, genome sequence data may replace SNP genotypes as markers. This could increase GS accuracy because the causative mutations should be included in the data.
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Integrated Genomic Approaches to Enhance Genetic Resistance in Chickens
Vol. 1 (2013), pp. 239–260More LessThe chicken has led the way among agricultural animal species in infectious disease control and, in particular, selection for genetic resistance. The generation of the chicken genome sequence and the availability of other empowering tools and resources greatly enhance the ability to select for enhanced disease resistance via genetic markers and to understand more deeply the biological basis of host resistance. In this review, we discuss how integrated genomic approaches are able to identify specific genes and genetic markers associated with disease resistance, give select examples of contemporary work involving various genomic strategies to identify disease resistance genes, and finish by giving some final thoughts on predicted applications in the near future.
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Conservation Genomics of Threatened Animal Species
Vol. 1 (2013), pp. 261–281More LessThe genomics era has opened up exciting possibilities in the field of conservation biology by enabling genomic analyses of threatened species that previously were limited to model organisms. Next-generation sequencing (NGS) and the collection of genome-wide data allow for more robust studies of the demographic history of populations and adaptive variation associated with fitness and local adaptation. Genomic analyses can also advance management efforts for threatened wild and captive populations by identifying loci contributing to inbreeding depression and disease susceptibility, and predicting fitness consequences of introgression. However, the development of genomic tools in wild species still carries multiple challenges, particularly those associated with computational and sampling constraints. This review provides an overview of the most significant applications of NGS and the implications and limitations of genomic studies in conservation.
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Phytase, a New Life for an “Old” Enzyme
Vol. 1 (2013), pp. 283–309More LessPhytases are phosphohydrolytic enzymes that initiate stepwise removal of phosphate from phytate. Simple-stomached species such as swine, poultry, and fish require extrinsic phytase to digest phytate, the major form of phosphorus in plant-based feeds. Consequently, this enzyme is supplemented in these species’ diets to decrease their phosphorus excretion, and it has emerged as one of the most effective and lucrative feed additives. This chapter provides a comprehensive review of the evolving course of phytase science and technology. It gives realistic estimates of the versatile roles of phytase in animal feeding, environmental protection, rock phosphorus preservation, human nutrition and health, and industrial applications. It elaborates on new biotechnology and existing issues related to developing novel microbial phytases as well as phytase-transgenic plants and animals. And it targets critical and integrated analyses on the global impact, novel application, and future demand of phytase in promoting animal agriculture, human health, and societal sustainability.
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Effects of Heat Stress on Postabsorptive Metabolism and Energetics
Vol. 1 (2013), pp. 311–337More LessEnvironmental-induced hyperthermia compromises efficient animal production and jeopardizes animal welfare. Reduced productive output during heat stress was traditionally thought to result from decreased nutrient intake. Our observations challenge this dogma and indicate that heat-stressed animals employ novel homeorhetic strategies to direct metabolic and fuel selection priorities independent of nutrient intake or energy balance. Alterations in systemic physiology support a shift in carbohydrate metabolism, evident through changes such as basal and stimulated circulating insulin levels. Hepatocyte and myocyte metabolism also show clear differences in glucose production and use during heat stress. Perhaps most intriguing, given the energetic shortfall of the heat-stressed animal, is the apparent lack of fat mobilization from adipose tissue coupled with a reduced responsiveness to lipolytic stimuli. Thus, the heat stress response markedly alters postabsorptive carbohydrate, lipid, and protein metabolism independently of reduced feed intake through coordinated changes in fuel supply and utilization by multiple tissues.
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Epigenetics: Setting Up Lifetime Production of Beef Cows by Managing Nutrition
R.N. Funston, and A.F. SummersVol. 1 (2013), pp. 339–363More LessLongevity of cattle is correlated to reproductive success. Many studies in different species report the influence of maternal nutrition on progeny performance, health, and reproduction. Maternal nutrient status can cause epigenetic alterations to the genome of the developing fetus, which potentially can impact future generations. This review discusses fetal programming mechanisms as well as maternal nutrition’s impact on placental development and progeny heifer performance and reproduction owing to nutrient restriction, age, or production status. Furthermore, we discuss how early neonatal nutrient intake and type can influence future productivity in the beef and dairy cow. Understanding how these factors influence progeny performance will enable cattlemen to produce replacement females better adapted to their environment through maternal nutrient regulation by stimulating fetal programming.
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Systems Physiology in Dairy Cattle: Nutritional Genomics and Beyond
Vol. 1 (2013), pp. 365–392More LessMicroarray development changed the way biologists approach the holistic study of cells and tissues. In dairy cattle biosciences, the application of omics technology, from spotted microarrays to next-generation sequencing and proteomics, has grown steadily during the past 10 years. Omics has found application in fields such as dairy cattle nutritional physiology, reproduction, and immunology. Generating biologically meaningful data from omics studies relies on bioinformatics tools. Both are key components of the systems physiology toolbox, which allows study of the interactions between a condition (e.g., nutrition, physiological state) with tissue gene/protein expression and the associated changes in biological functions. The nature of physiologic and metabolic adaptations in dairy cattle at any stage of the life cycle is multifaceted, involves multiple tissues, and is dynamic, e.g., the transition from late-pregnancy to lactation. Application of integrative systems physiology in periparturient dairy cattle has already advanced knowledge of the simultaneous functional adaptations in liver, adipose, and mammary tissue.
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In Vivo and In Vitro Environmental Effects on Mammalian Oocyte Quality
Vol. 1 (2013), pp. 393–417More LessThe oocyte is at the center of the equation that results in female fertility. Many factors influence oocyte quality, including external factors such as maternal nutrition, stress, and environmental exposures, as well as ovarian factors such as steroids, intercellular communication, antral follicle count, and follicular fluid composition. These influences are interconnected; changes in the external environment of the female translate into ovarian changes that affect the oocyte. The lengthy period during which the oocyte remains arrested in the ovary provides ample time and opportunity for environmental factors to take their toll. An appropriate environment for growth and maturation of the oocyte, in vivo and in vitro, is critical to ensure optimal oocyte quality, which determines the success of fertilization and preimplantation embryo development, and has long-term implications for implantation, fetal growth, and offspring health.
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The Equine Endometrial Cup Reaction: A Fetomaternal Signal of Significance
Vol. 1 (2013), pp. 419–442More LessA remarkable feature of equine pregnancy is the development of the invasive trophoblast of the chorionic girdle and its formation of the gonadotrophin-secreting endometrial cup cells in early gestation. The details of this process have been revealed only slowly over the past century, since the first description of the endometrial cups in 1912. This centennial presents an opportunity to review the characteristics of the cells and molecules involved in this early, critical phase of placentation in the mare. The invasiveness of the chorionic girdle trophoblast appears to represent an atavistic attribute more commonly associated with the hemochorial placentae of primates and rodents but not with the more recently derived epitheliochorial placentae of the odd-toed ungulates. The nature of and raison d’être for the strong fetal signals transmitted to the mare by the endometrial cup reaction, and her responses to these messages, are the subject of the present review.
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The Evolution of Epitheliochorial Placentation
Vol. 1 (2013), pp. 443–467More LessEpitheliochorial placentation is a derived condition and has evolved separately in strepsirrhine primates and laurasiatherians (pangolins, whales, and hoofed mammals). Usually it is associated with a long gestation period, small litters, and precocial young. Oxygen transfer is facilitated by indenting of the uterine and trophoblast epithelia by maternal and fetal capillaries, respectively. Histotrophic nutrition is important, and adaptations include areolas and hemophagous regions. In pigs and horses, for example, iron is transported as uteroferrin secreted from the uterine glands and taken up by areolas. In the horse, invasive trophoblast cells form cups within the endometrium that are the source of equine chorionic gonadotropin. In ruminants, binucleate trophoblast cells fuse with uterine epithelial cells to form trinucleate cells or plaques that secrete pregnancy hormones. There is evidence of immunosuppression in connection with these more invasive types of trophoblasts. The epitheliochorial condition may be advantageous for long pregnancies in large animals.
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The Role of Productivity in Improving the Environmental Sustainability of Ruminant Production Systems
Vol. 1 (2013), pp. 469–489More LessThe global livestock industry is charged with providing sufficient animal source foods to supply the global population while improving the environmental sustainability of animal production. Improved productivity within dairy and beef systems has demonstrably reduced resource use and greenhouse gas emissions per unit of food over the past century through the dilution of maintenance effect. Further environmental mitigation effects have been gained through the current use of technologies and practices that enhance milk yield or growth in ruminants; however, the social acceptability of continued intensification and use of productivity-enhancing technologies is subject to debate. As the environmental impact of food production continues to be a significant issue for all stakeholders within the field, further research is needed to ensure that comparisons among foods are made based on both environmental impact and nutritive value to truly assess the sustainability of ruminant products.
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Making Slaughterhouses More Humane for Cattle, Pigs, and Sheep
Vol. 1 (2013), pp. 491–512More LessWhen a stunning method is being evaluated, it is essential that the animal-handling and restraint methods that are used with it are also examined. This makes it possible to determine the effect of the entire system on animal welfare. Cattle, pigs, and sheep will move easily through the races at a slaughter plant if visual distractions such as reflections on shiny metal, dangling chains, moving equipment, or people up ahead are removed. The most important scientific research on captive bolt, CO2, and electrical stunning methods is reviewed. A common mistake made by people evaluating insensibility is to misinterpret reflexive leg kicks as a sign of return to sensibility. When religious slaughter is being evaluated, the variable of how the animal is restrained must be separated from the variable of slaughter without stunning. Slaughter can be done with a high level of animal welfare.
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