Sheep

Sheep have been used as models in medical research since 1667, when a French physician transfused a 15-year-old boy with blood from a lamb. Since the lamb's blood was incompatible with the boy's body chemistry, this experiment led to further work on the compatibility of blood for transfusion.

The arteriovenous shunt is a device which allows for use of hemodialysis for patients with kidney disease. The materials used to construct the first successful shunt, allowing patients with kidney failure to be connected to dialysis machines for long-term treatment, were perfected through research in sheep with kidney failure. The surgical techniques for implanting these shunts were also developed in sheep.

Pregnant female sheep, or ewes, have been used extensively as models for human pregnancy. Unlike other laboratory animals, sheep have very short gestation periods and give birth to lambs with birth weights similar to those of human babies.

This research has led to an understanding of the hormonal changes that occur in mother and fetus shortly before birth, as well as to improved treatment methods of respiratory distress in premature infants. This work has also contributed to an understanding of patent ductus arteriosus.

Other areas in which sheep have proven to be useful models include research on aneurysms, joint reconstruction, fetal alcohol syndrome, organ transplantation, and decompression sickness.

Sheep were also essential to research which led to a vaccine for anthrax, an infectious disease of farm animals which can be transmitted to people.