Composition of the milk of the common marmoset (Callithrix jacchus) and milk substitutes used in hand-rearing programmes, with special reference to fatty acids

Preferential sugar utilization by bifidobacterial species

Aim: Bifidobacteria benefit host health and homeostasis by breaking down diet- and host-derived carbohydrates to produce organic acids in the intestine. However, the sugar utilization preference of bifidobacterial species is poorly understood. Thus, this study aimed to investigate the sugar utilization preference (i.e., glucose or lactose) of various bifidobacterial species. Methods: Strains belonging to 40 bifidobacterial species/subspecies were cultured on a modified MRS medium supplemented with glucose and/or lactose, and their preferential sugar utilization was assessed using high-performance thin-layer chromatography. Comparative genomic analysis was conducted with a focus on genes involved in lactose and glucose uptake and genes encoding for carbohydrate-active enzymes. Results: Strains that preferentially utilized glucose or lactose were identified. Almost all the lactose-preferring strains harbored the lactose symporter lacS gene. However, the comparative genomic analysis could not explain all their differences in sugar utilization preference. Analysis based on isolate source revealed that all 10 strains isolated from humans preferentially utilized lactose, whereas all four strains isolated from insects preferentially utilized glucose. In addition, bifidobacterial species isolated from hosts whose milk contained higher lactose amounts preferentially utilized lactose. Lactose was also detected in the feces of human infants, suggesting that lactose serves as a carbon source not only for infants but also for gut microbes in vivo. Conclusion: The different sugar preference phenotypes of Bifidobacterium species may be ascribed to the residential environment affected by the dietary habits of their host. This study is the first to systematically evaluate the sugar uptake preference of various bifidobacterial species.

Molecular evolutionary insights from PRLR in mammals

Prolactin (PRL) is a pleiotropic neurohormone secreted by the mammalian pituitary gland into the blood, thus reaching many tissues and organs beyond the brain. PRL binds to its receptor, PRLR, eliciting a molecular signaling cascade. This system modulates essential mammalian behaviors and promotes notable modifications in the reproductive female tissues and organs. Here, we explore how the intracellular domain of PRLR (PRLR-ICD) modulates the expression of the PRLR gene. Despite differences in the reproductive strategies between eutherian and metatherian mammals, there is no clear distinction between PRLR-ICD functional motifs. However, we found selection signatures that showed differences between groups, with many conserved functional elements strongly maintained through purifying selection across the class Mammalia. We observed a few residues under relaxed selection, the levels of which were more pronounced in Eutheria and particularly striking in primates (Simiiformes), which could represent a pre-adaptive genetic element protected from purifying selection. Alternative, new motifs, such as YLDP (318-321) and others with residues Y283 and Y290, may already be functional. These motifs would have been co-opted in primates as part of a complex genetic repertoire related to some derived adaptive phenotypes, but these changes would have no impact on the primordial functions that characterize the mammals as a whole and that are related to the PRL-PRLR system.

Estimates of milk constituents from lactating bonnet macaque (Macaca radiata) mothers between two and seven months post-partum

BACKGROUND

The literature regarding milk composition in non-human primates collected across offspring development is limited. We assayed milk samples from bonnet macaque (Macaca radiata) mothers as part of studies characterizing development of this species.

METHODS

Milk was obtained when possible longitudinally from seven lactating bonnet macaque mothers. Samples were frozen until analysis. Individual samples were analyzed to determine the concentrations of electrolytes including sodium, potassium, calcium, chloride, and magnesium, as well as urea, protein, lipids, glucose, and lactose.

RESULTS

A trend for increased lipids as well as protein percentage was noted with increasing infant age. Chloride and calcium showed an increase with age, whereas other electrolytes remained relatively stable across development.

CONCLUSIONS

The composition of the milk of this particular macaque species was similar to other Old World primates as well as humans. These data add to the limited information available on milk constituents among mammals.

Does the milk of Callitrichid monkeys differ from that of larger anthropoids?

The generalization that anthropoid primates produce dilute milks that are low in protein and energy is based primarily on data from large monkeys of the families Cebidae and Cercopithecidae, as well as humans. The marmosets and tamarins (Callitrichidae) are not only much smaller in body size, but also typically raise multiple offspring during a relatively brief lactation. We hypothesized that selection for small body size and high reproductive rate might favor secretion of milk of higher energy and protein concentrations. To test this hypothesis, 46 milk samples collected from 10 common marmosets (Callithrix jacchus, ca. 350 g) were assayed for dry matter (DM), crude protein (CP), fat, and sugar; and gross energy (GE) was calculated from these constituents. We also assayed five samples collected from three golden lion tamarins (Leontopithecus rosalia, ca. 700 g) and six samples collected from a single pygmy marmoset (Cebuella pygmaea, ca. 150 g) over two lactation periods. All samples were collected between days 10 and 57 post partum, representing mid lactation for these species. The milks of these three species were similar, containing 14.0%, 16.1%, and 13.7% DM; 2.7%, 2.6%, and 2.9% CP; 3.6%, 5.2%, and 3.7% fat; 7.4%, 7.2%, and 7.8% sugar; and 0.76, 0.90, and 0.82 kcal/g for common marmosets, golden lion tamarins, and the pygmy marmoset, respectively. These species produced milks with energy values that were within the range reported for large anthropoids, albeit with slightly higher protein concentration. However, milk composition did vary substantially among individual common marmoset females, especially in the proportion of milk energy derived from fat. In contrast, CP as expressed as a percent of GE was remarkably constant among common marmoset females. Callitrichid milk appeared to be similar to that of larger anthropoid primates in GE, but was higher in CP and in the proportion of GE from CP. However, the small sample sizes for the golden lion tamarin and the pygmy marmoset, and the wide variation in milk composition found among common marmoset females cautions against definitively characterizing the milks of callitrichids from these data.

Milk composition reflects pattern of maternal care in prosimian primates

Hypothesized relationships between milk composition and life history traits were examined by analyzing mid-lactation milks of seven lemurs (Eulemur fulvus, E. macaco, E. rubriventer, E. mongoz, Varecia variegata, Hapalemur griseus, Lemur catta), three bushbabies (Otolemur crassicaudatus, O. garnettii, Galago moholi), and two lorises (Nycticebus coucang, Loris tardigradus); partial data were also obtained for the lemuroid Cheirogaleus medius. There were no significant differences in milk composition among species within either Eulemur or Otolemur, but the four genera for which multiple samples were available (Eulemur, Varecia, Otolemur, and Nycticebus) exhibited large composition differences. Eulemur milk was, on average, very dilute (9.9% dry matter) and low in energy (0.49 kcal/g). These milks contained 0.9% fat, 1.2% protein, and 8.4% carbohydrate on a fresh weight basis. Protein energy comprised only about 15% of total milk energy. Varecia had significantly higher dry matter (13.5%), fat (3.2%), protein (4.2%), gross energy (0.80 kcal/g), and protein energy:total energy ratio (28%) than Eulemur. Milks of the lorisoid genera Otolemur and Nycticebus were very similar, and both had significantly higher dry matter (18.3, 16.3%), fat (7.6, 7.0%), and gross energy concentration (1.27, 1.13 kcal/g) than either lemuroid genus. Otolemur milk was higher in protein than Nycticebus milk. We conclude that lorises, bushbabies, and perhaps cheirogaleids produce relatively rich, energy-dense milks in comparison with anthropoid primates. However, dilute milks appear to be uniformly found among species of Eulemur and perhaps in Lemur catta. The milk of Varecia (and perhaps Hapalemur) is intermediate in composition. Differences in milk composition among prosimians may be related to differences in maternal care: prosimians that carry their young during lactation produce more dilute milks than do species which leave their young unattended for prolonged periods. When looking at primates as a whole, however, the picture somewhat less clear, since the milks of some "parkers" like Varecia do closely resemble those of large anthropoid primates who carry their young.

'Collaborative' rearing of marmoset triplets

A system of management is described in which all 3 offspring from triplet births to Callithrix jacchus can be successfully reared to weaning. Hand-rearing techniques are applied to the offspring in turn without depriving them of the maternal and family influences necessary for normal behavioural development.