GLUTAMINE, BUT NOT GLUTAMATE, CONCENTRATIONS CHANGE IN EQUINE MILK DURING LACTATION

Abstract

Recently it has been realized that glutamine (gln) and glutamate (glu) are the most abundant amino acids in mammalian milk. The aim of this study was to determine the gln and glu concentration in blood and milk in Quarter‐Horse mares during lactation. Nineteen (19) mares were used and samples were collected: after 8 hours parturition, and every 30 days until weaning (180 days after birth). Data were analyzed by ANOVA and Tukey's test, with P<0.05. Blood [glu] was 0.289±0.047 mol/mL at parturition day and when was 0.146+0.117 mol/ml at the end of the lactation, without significant changes (P>;0.05). In contrast, blood [gln], which was 0.582+0.078mol/mL at parturition, decreased to 0.300±0.032mol/mL at weaning (~52%). In milk, [gln] was 0.738+0.113 mol/ml 8h after delivery, increase to 1.333±0.198 mol/ml at 3 months of lactation, and then decreased to 0.511±0.098 mol/mL at weaning. Also, [glu] changes significantly, with large concentration observed at 3rd month of lactation (0.862±0.085 mol/ml) and lowest at parturition (0.449±0.057 mol/ml). These changes in blood and milk gln content indicate major changes in glutamine but the site of synthesis, skeletal muscle or mammary gland remains to be determined.