Research

The research programs of the Department of Poultry Science range from quite fundamental to applied, with many having direct application to Pennsylvania's commercial poultry industry. Current ongoing research examines the regulation of biolgical clocks, functional and integrative genomics, the modification of egg composition, avian reproduction and management, skeletal biology, environmental poultry management, and molecular and metabolic endocrinology. In addition to improving the efficiency of production and wholesomeness of poultry meat and eggs, strategies for the management of wastes and by-products of poultry production are currently being addressed from an environmental standpoint.  Meat-bird research encompasses neuroendocrine regulation of muscle and adipose tissue deposition, genetic influences on growth and development, attenuating reproductive problems in commercial strains of broilers and turkeys, and the cellular basis of bone formation and resorption.  At the cellular and molecular level of investigation, these research efforts have significant biomedical relevance as well.  Egg production, quality, nutrient composition, and safety are also being addressed by Penn State poultry scientists.  Other program areas transcend avian species, such as the regulation of biological clocks and their influence on behaviors, life history stages, and reproduction.

 

The departent houses a laboratory to research the regulation of biological clocks at the systems level in birds.  Behavioral, molecular, and electrophysiological techniques are used to understand the neural and endocrine mechanisms by which these daily clocks and yearly calendars control the temporal organization of behaviors and life history stages. Current projects are broadly focused along two categories: the determination that biological clocks temporally organize pre-migratory and migratory behaviors; and identifying the sgnals that the biological clock transmits or amplifies in the initiation of reproductive development and maintenance of reproductive viabilty. Currently, we seek to identify the changes in protein and gene expression that allow normally diurnal birds to become nocturnally active during migration, functioning at a high performance level despite very little sleep.  

Our functional and integrative genomics research, focuses on the physiological genetics of growth and development. A portion of his work centers on genetic variation in the reproductive aspects of gene transmission. Work involving the male reproductive system, specifically genetic relationships of sperm membrane characteristics, has resulted in a novel method to evaluate the fertilizing ability of sperm from a variety of the avian (Peking duck, turkey, and Japanese quail) to the mammalian (rat and mouse) species. Furthermore, we have begun to concentrate on genetic elements of the oocyte. Recent studies have demonstrated the inheritance of a novel protein isolated from the chicken oocyte that accounts for approximately 65 percent of idiopathic female infertility among broiler-type chickens. We are also investigating several environmental and pharmacological agents that influence this family of genes. Continued work will elucidate the mechanisms of action.

 

Research in the modification of egg compositions is centered in the metabolic effects of dietary modification in domestic fowl and their subsequent influence on the composition of poultry products consumed by humans. Specifically, our research centers on the alteration of cholesterol and lipoprotein metabolism in laying hens, with the overall goal of producing consumable eggs with markedly reduced fat and cholesterol contents.

 

Avian reproduction and management research investigates commercial broiler and turkey reproductive problems and opportunities. The program has involved both university-based studies and field research conducted in collaboration with companies in their hatcheries or breeder operations. Research topics include sperm cell management, egg-hatching incubation, and breeder male and female body weight control. Management studies involving market broilers and turkeys are conducted to determine the environmental and nutritional factors that can optimize growth, meat yield, and carcass quality. All studies involve the immediate application and adoption of research principles to aid the commercial poultry industry.

 

The overall goal of the skeletal biology research program is to develop an understanding of the key physiological processes involved in avian skeletal metabolism. One tissue under investigation is the epiphyseal growth plate, the tissue responsible for longitudinal bone growth. Chondrocytes in this tissue undergo an intricate series of developmental steps culminating in the replacement of cartilage by metaphyseal bone.  Disruption of this process can result in a wide variety of skeletal abnormalities such as dwarfism, rickets and tibial dyschondroplasia (TD).  The latter condition (TD) is common in rapidly growing broilers and turkeys. Our recent research has utilized gene expression and immunolocalization of gene products to study this skeletal abnormality, with results leading to the development of a hypothesis which explains the pathophysiology of TD. Current research involves the use of microarray technology to gain a wider perspective on gene expression in normal growth plate tissue with a second area of research centering on medullary bone, a tissue that is unique to laying avians and serves as a source of calcium for egg shell formation.  In commercial laying hens medullary bone provides 30 to 40 percent of the calcium in each egg shell, and it is our hypothesis that medullary bone has a unique composition which allows for the daily cycling of calcium for egg shell formation. We are in the process of isolating and identifying the matrix components of medullary bone responsible for the different staining and calcium exchange properties of this tissue.

 

The department heads a combined research and extension program in environmental poultry management.  Research efforts in this area focus on discovering and promoting efficient poultry production systems that place a minimum burden on the environment.  While managing manure nutrients, emissions, and by-products of poultry production are obvious endeavors, less tangible efforts include the impact of odor, flies, traffic, etc., on the environment at the urban-rural interface. Other research efforts emphasize egg production, quality, and food safety.

 

Research performed in th molecular endocrinology laboratory is interested in characterizing the influence of adipose tissue hormones on avian growth and reproduction.  Adipose tissue is considered an endocrine organ secreting a variety of hormones that are involved in the development of obesity, cardiovascular diseases, diabetes, cancer, and reproductive disorders. Our laboratory has cloned the chicken genes that encode for two adipose tissue hormones, adiponectin and visfatin. We are determining the factors that influence the biological functions and formation of multimeric forms of adiponectin and visfatin. Overall, we are interested in characterizing the physiological role of adiponectin and visfatin on carbohydrate and lipid metabolism, hypothalamic control of pituitary gland function and gonadal functions. Additionally, our laboratory is studying the neuroendocrine control of female reproduction, as we are elucidating the role of a novel neuropeptide, gonadotropin-inhibitory hormone, and its receptor in controlling pituitary hormone secretion and ovarian follicular maturation. We use a variety of experimental approaches to study gene and protein expression along with post-translational modifications at the cellular, tissue and organismal levels.

 

Our metabolic endocrinology laboratory, focuses on the biological actions of growth hormone (GH), with emphasis on components of the signal transduction pathway that are essential for GH action. We have found through this research that chronic GH induces expression of JAK2 protein and tyrosine phosphorylation in liver and skeletal muscles, and that this expression is tissue-specific with respect to JAK2 isoforms. An important focus of this lab is on the metabolic effects of GH, specifically, regulation of hepatic type III iodothyronine deiodinase (5DIII) gene expression, and have found that GH decreases 5DIII message, ultimately resulting in a secondary hyperthyroid state in vivo, with loss of skeletal muscle mass. Although GH has long been recognized to have direct metabolic effects, and is currently administered to non-GH deficient children and adults for therapeutic purposes, the unrecognized consequences for growth or even preservation of muscle mass may be significant. A recent new emphasis in our laboratory, in collaboration with Dr. Ramachandran's laboratory, is the role and regulation of adiponectin in avian models.