The development and distribution of mucosal enzymes in the small intestine of the fetus and young foal.

This study investigates the development and distribution of mucosal enzymes in the small intestine of unborn and newborn horses, finding that some enzymes reach peak levels at birth then decrease, while others slowly increase to adult levels by approximately seven months.

Mucosal enzymes in fetal intestine

• The enzymes lactase and cellobiase are present in the fetal intestine from the third month of gestation. There is little change in their levels by the ninth month.
• However, at birth, these enzymes reach their maximum levels and then gradually decrease after four months.

Development of maltase, sucrase, and trehalase

• Contrary to lactase and cellobiase, enzymes such as maltase, sucrase and trehalase barely exist in the fetus’s system.
• Maltase is present only in low amounts at birth. However, during the suckling period, all these enzymes increase to reach their adult levels when the foal is around seven months old.

Alkaline phosphatase activity and other mucosal enzymes

• The activity of the enzyme alkaline phosphatase matures faster than that of the disaccharidase enzymes.
• Except for alkaline phosphatase, other mucosal enzymes are almost completely absent from meconium (the first stool of a mammalian infant) and the large intestine.

Implications for lactose ingestion

• Due to the observed decrease in lactase levels after birth, continuous ingestion of lactose could be harmful to foals suffering from severe diarrhea, as their bodies may lack the necessary lactase to properly digest lactose.