Supplementary material from "Milk metabolite composition of a semi-captive population of Asian Elephants"

Lack of maternal milk commonly leads to Asian elephant calves’ death in captivity. Currently available supplements seem inefficient. Hence we aimed at characterising the composition of Asian elephant milk to provide information on calves’ nutritional needs. Seventy milk samples from 22 Asian elephants living in semi-captivity in their natural environment in Myanmar were collected. Total protein content, free amino acids, organic acids of the tricarboxylic acid cycle, acylcarnitines, phospholipids and fatty acids were analysed.. Associations with lactation stage (months postpartum) were investigated through repeated measure mixed models. We identified 160 compounds: 22 amino acids, 12 organic acids of the tricarboxylic acid cycle, 27 fatty acids, 15 acyl-carnitines and 84 phospholipids. The milk contained substantial amounts of free glutamate (Median: 1727.9, Interquartile range (IQR):1278.4 μmol/L) and free glycine (2541.7, IQR:1704.1 μmol/L). The fatty acid profile was mostly constituted by saturated fatty acids, particularly capric acid (40.1, IQR:67.3 g/L). Milk samples also contained high amounts of carnitines, phospholipids and organic acids. The wide array of nutritional metabolites identified and quantified, some of which present high concentrations in the milk from this species as opposed to other species, suggests underpinning physiological functions that might be crucial for the survival of Asian elephant calves.