as well as their cohorts who dissected animals. Development The size of the fetal pig depends on the time allowed for the mother to gestate: Nutrition No studies have found significant data regarding the mother swine’s diet and fetal pig survival rate. However, there is a correlation between a mother pig having a nutritious diet containing proteins, vitamins and minerals during gestation period and the survival rate of piglets. The correlation, however, is not statistically different. Weight is also not a factor of survival rate because a healthier diet does not lead to a heavier offspring or a greater chance of live birth. Placental development The placenta is used as a means of transferring nutrients from the mother to the fetus. The efficiency at which nutrients are transferred dictates the health and growth of the fetus. FRP, or fetal weight: placental weight ratio, was commonly used to determine placental efficiency. However, increasing FPR does not prove to increase litter size. Instead, a more accurate way of determining fetus growth is through certain characteristics of the placental lining. The placenta is made of a folded trophoblast/endometrial epithelial bilayer. The width and length of the placenta folds are positively related and increase as gestation progresses. The width of the placental folds decreases until day 85 of gestation. From here, the width increases with gestation and is at its largest around day 105. The rate at which these folds increase is negatively related to fetus size. Thus, greater fold widths will be seen in smaller fetuses. Although increasing placental fold width does increase the interaction between fetus and mother, nutrient exchange is not most efficient in smaller fetal pigs, as would be expected. Many other factors, including depth of placental folds, are also responsible for these interactions. Prenatal development The prenatal development of the fetus includes all the tissue and organ development. Within hours of mating, the sperm and egg undergo fertilization in the oviduct and three days later the egg moves into the uterus. The cells begin to specialize by day six, and attach themselves to the uterus lining by day eleven. From fertilization to day 18, the endoderm, ectoderm and mesoderm have been forming inside the embryo, and are completely formed by day 18, the same day the placenta forms. The endoderm transforms into the lungs, trachea, thyroid gland, and digestive tract of the fetus. The ectoderm has a greater role