Macronutrient composition of milk from captive southern pig‐tailed macaques (Macaca nemestrina)

Abstract

Milk composition is a fundamental aspect of mammalian reproduction. Differences in milk composition between species may reflect phylogeny, dietary ecology, lactation strategy, and infant growth patterns, but may also vary within a species due to maternal body condition. This study presents the first published data on milk macronutrient composition of southern pig‐tailed macaques (Macaca nemestrina) and compares the results with data on two other Cercopithecine species. Milk samples were obtained from five dams at 10‐ and 14‐weeks postparturition. Macronutrient composition was determined at the Smithsonian's National Zoo and Conservation Biology Institute using proven methods developed over 30 years. On average (±SEM), the milk contained 83.9 ± 0.4% water, 6.7 ± 0.4% fat, 7.6 ± 0.1% sugar, 1.8 ± 0.1% protein, and 0.22 ± 0.01% mineral content. The Ca:P ratio was 1.8; concentrations of Ca and protein were correlated. Mean gross energy was 1.02 ± 0.03 kcal/g with most of the energy coming from fat (59.6 ± 1.5%), followed by sugar (29.9 ± 1.4%) and protein (10.5 ± 0.5%). The milks at 14 weeks of infant age were higher in energy than the milks at 10 weeks, with an increase in energy from fat (p = 0.005) and decrease in energy from sugar (p = 0.018). The energy from protein did not change (p = 0.272). Compared to captive rhesus macaque (Macaca mulatta) and olive baboon (Papio anubis) milk assayed by identical methods, captive pig‐tailed macaque milk was higher in energy, but after accounting for the higher milk energy there was no difference in the proportions of milk energy from protein, fat, and sugar. The captive pig‐tailed dams were significantly heavier than reported values for wild pig‐tailed macaques, suggesting high body condition. High body condition in captive Cercopithecines appears to result in milk higher in energy, with more energy coming from fat and less from sugar. However, variation in the proportion of milk energy from protein in captive Cercopithecine milks appears relatively constrained.

Local environment shapes milk microbiomes while evolutionary history constrains milk macronutrients in captive cercopithecine primates

“…We calculated gross energy (GE) using the following energy values: 3.95 kcal/g for sugar, 9.11 kcal/g for fat, and 5.86 kcal/g for protein (Perrin, 1958). This method of GE calculation has been shown to agree with experimentally measured GE using adiabatic bomb calorimetry for milk from multiple species including rhesus macaques (Hinde et al, 2009) and, specifically, the pig‐tailed macaque samples used in this study (Glick & Power, 2024). Using the calculated GE, the percentages of GE from fat, sugar, and protein were determined for all samples.…”

“…All four species fall roughly on the same linear pattern, although the pig‐tailed macaque samples in this study differ in all being of relatively high GE and displaying less variation than the other species. A comparison of the milk composition of the SNPRC rhesus macaque and olive baboons against a larger number of pig‐tailed macaque milk samples showed greater overlap and no significant difference in milk composition after accounting for milk GE (Glick & Power, 2024). Nevertheless, the data on weight for individuals in this study was confounded with species‐specific variation in body mass (i.e., olive baboons are a larger species and thus had greater weights, but were not necessarily over‐conditioned), making it difficult to definitively determine whether individuals were overweight.…”

“…In addition, we analysed overall milk nutrient composition by calculating measures of Bray–Curtis distance based on all GE proportions of all three nutrients. Data for the milk macronutrient composition of the pig‐tailed macaque (Glick & Power, 2024) and olive baboon and rhesus macaques from SNPRC (Glick et al, 2021) are published. The milk macronutrient data for the Japanese macaques and the rhesus macaques from ONPRC were analysed for this study.…”