1Nutrition Laboratory, Smithsonian Conservation Biology Institute, National Zoological Park, 2Anthropology, The George Washington University, 3Veterinary Care, Fresno Chaffee Zoo, 4Anthropology, Indiana University, 5Research Department, American College of Obstetricians and Gynecologists
Thursday Evening, Park Concourse
Data on milk composition of nonhuman apes are essential for testing hypotheses about derived features of human milk composition, and for understanding species-specific infant nutritional requirements and links between ontogeny and lactation. These comparative data are rare, particularly from orangutans. Here we report on longitudinal milk samples (n = 15) collected between 6-12 months of lactation from a Sumatran orangutan (Pongo abelii) at the Fresno Chaffee Zoo. Each sample was assayed for nutrients [dry matter (DM), crude protein (CP), fat, sugar, and ash (total mineral)], the metabolic hormone adiponectin, the growth factors epidermal growth factor (EGF), transforming growth factor beta 2 (TGF-β2), and their receptors (EGF-R and TGFβ-R3). The nutrients and bioactive molecules are expressed as a concentration (percent for nutrients, pg/ml for other molecules) and on a per energy basis (mg/kcal, pg/kcal), with gross energy (GE) calculated from CP, fat and sugar. Mean nutrient values are: DM=11.3% (SD=1.8%); CP=0.8% (0.2%), fat=2.9% (0.8%); sugar=7.4% (1.4%); ash= 0.13% (0.05%); GE=0.535kcal/g (0.096 kcal/g). Nutrient composition was not related to infant age whether expressed as concentration or per kcal. Concentrations of adiponectin (r=-.846, p=.001), TGFβ-R3 (r=-.630, p=.038) and EGF (r=-.569, p=.068) declined with infant age, but appear relatively constant over lactation when expressed as pg/kcal (p>.2, all molecules). Adiponectin was positively correlated with EGF (r=.789, p=.004) and TGFβ-R3 (r=.860, p=.001). These correlations were strengthened when expressed as pg/kcal. These findings suggest that mammary synthesis of these molecules may be linked to other metabolic pathways in the orangutan, and possibly other apes, including humans.
This study was partially funded by the GW-SI Opportunity Fund Research Grant "Endocrine Signaling via Milk in Primates" to RB and MP.