Early conceptus loss causes a significant financial burden to horse breeders. In the January 1998 issue of the Lloyd’s Equine Disease Quarterly, maternal recognition of pregnancy and the relationship of progesterone, prostaglandin F2a(PGF) and oxytocin were discussed. This article will examine some aspects of the communication that occur between the conceptus and the maternal environment during the first few critical weeks of gestation.

One of the current researcher’s approaches in studying conceptus-maternal interactions is to look at changes in protein production. They have examined proteins synthesized and released by equine conceptuses and from uterine endometrium and oviducts of cycling and pregnant mares. Major proteins synthesized and secreted by the uterine endometrium include retinol binding protein and oxytocin.

Retinol binding protein carries metabolites of vitamin A to the developing embryo and placenta. Studies in laboratory animals have shown that these metabolites are responsible for proper formation of the developing embryo. Either too much or too little of the vitamin A metabolites are lethal to the embryo. Uterine oxytocin may be involved in regulating PGF production and maternal recognition of pregnancy, as discussed previously.

Major protein products of the equine conceptus include transferrin and alpha-fetoprotein. Transferrin services to carry iron to the developing embryo and placenta. Iron is important in a variety of functions, including formation of hemoglobin, and is necessary during early development to establish the circulatory system for the embryo and the placenta. Transferrin also functions in cell growth, immunoregulation and organ differentiation.

Alpha-fetoprotein serves a variety of functions, including