Impact of Thyroid Perturbation on Pre- and Postnatal Growth and Development in Swine

Modern swine have the genetic potential for astounding growth and efficiency. However achieving this potential on farm requires metabolic and physiologic stability despite unavoidable disruptions. Thyroid hormones are the master regulator of metabolic activity, with additional functions in controlling fetal development, postnatal growth and lean muscle deposition. Our work has demonstrated that swine are particularly susceptible to thyroid perturbations following pathogenic infection and this response is strongly correlated with fetal development and postnatal performance. Further, our preliminary data indicates that non-pathogenic stressors associated with routine management induce similar effects. As yet, the direct cause and effect relationship between thyroid function and growth and development has not been established. Thus, the objectives of this proposal are 1) Investigate thyroidal responsiveness to postnatal stressors and the subsequent impacts on growth performance and gut function; and 2) Investigate the role of thyroid hormones in fetal and perinatal development. To accomplish Objective 1 we will evaluate thyroid biology following weaning, transport and feed withdrawal, and then use an established model of non-pathogenic hypothyroidism to study the cause-effect relationship with growth and gastrointestinal function. To accomplish Objective 2 we will evaluate thyroid hormones in low birth weight piglets and the relationship with subsequent development, and then characterize the impact of thyroid disruption during discrete periods of fetal development. The primary outcomes will be an improved understanding of porcine thyroid biology and impact of perturbations in this system on subsequent growth and intestinal function. Program Area Priority: Metabolic disorders and nutritional de?ciencies affecting production of meat.