Jeffrey L. (Jeff) Vallet
The primary goal of Dr. Vallet's research is to increase the number of piglets weaned per sow. The number of piglets weaned depends on the number of fully formed piglets at farrowing, the stillbirth rate, and preweaning mortality. The number of fully formed piglets is primarily limited by uterine capacity, and Dr. Vallet's studies on uterine capacity focus on the role of placental development in the efficiency of nutrient transport to the fetus during gestation. These studies focus primarily on development of the folded epithelial bilayer that makes up the functional unit of the pig placenta. Another set of experiments deals with control of the farrowing process, specifically those factors that determine the length of birth intervals of individual piglets, since this has a profound effect on stillbirth rate. Birth intervals shorten as litter size increases, and the mechanisms controlling this relationship are not known but do not appear to be due to placental estrogen, reductions in birth weight in response to increased litter size, or the occurrence of empty uterine space that occurs in small litters in utero. Finally, studies on factors influencing preweaning mortality currently focus on the role of brain myelination in neonatal piglet survival and the role of dam initiation of lactation and neonatal piglet nursing ability on preweaning survival. The latter studies deal with the use of the "immunocrit," a rapid and simple measure of neonatal piglet serum IgG concentrations, for assessing the dam-piglet nursing interaction.