Donna G. Layne

Lactation, maternal behavior and infant growth in common marmoset monkeys (Callithrix jacchus): effects of maternal size and litter size

Abstract. We examined the relationship between lactation performance and infant growth in a captive population of common marmosets (Callithrix jacchus) that varied in both maternal and litter size. Though common marmosets display a typical primate pattern of dilute milk and relatively slow infant growth rates (factors associated with low daily lactation investment and minimal maternal size effects), we hypothesized that the marmosets small body size would make lactation investment more sensitive to maternal size than is true for larger-bodied primates. Smaller mothers rearing twins had lower milk fat, lower gross energy in milk samples collected in mid to late lactation and lower nursing-bout frequencies than did large mothers nursing twins. Lactation performance and maternal behavior did not differ between large and small mothers when rearing singletons, with a single exception: small mothers had a lower gross energy in mid-lactation milk samples. Relative growth rates in twins but not singletons were affected by maternal size, such that small mothers supported more growth per infant when rearing singletons while large mothers supported more growth per infant when rearing twins. Among the larger mothers, only, older mothers supported somewhat, though not significantly, less growth per infant, regardless of litter size. Twin infants of small mothers appeared to respond to below-optimal levels of milk yield by initiating maternal carrying less often. The relative energy intake of mothers was similar regardless of litter or maternal size. Small mothers rearing twins drew more heavily on reserves, reflected in a linear weight loss during lactation; however, the reserves drawn upon were inadequate to meet the lactation demand, resulting in lower milk energy output. In addition, small mothers rearing twins were more likely to be ill and less likely to be fertile in the year following lactation than were large mothers of twins or mothers of any size rearing singletons.

Energy restriction initiated at different gestational ages has varying effects on maternal weight gain and pregnancy outcome in common marmoset monkeys (Callithrix jacchus)

With relatively high fertility and short lifespan, marmoset monkeys (Callithrix jacchus) may become useful primate models of prenatal nutritional effects on birth condition and adult disease risk. The present study determined the effects of energy restriction to 75% of expected ad libitum consumption during mid- (day 66) or late (day 99) gestation on maternal weight, fetal growth and pregnancy outcomes in this species. Mid-restriction reliably induced the loss of pregnancy before term, at 92 d, on average. Of the late-restricted pregnancies, four of seven were normal term length while three were preterm deliveries, at 101, 117 and 132 d. Control females had a mean mid-pregnancy weight gain of 0.67 g/d while mid-restricted females lost -0.65 g/d, on average. Control pregnancies averaged a 1.06 g/d gain during late pregnancy, while energy-restricted females lost -0.67 g/d, on average. Restriction-related weight change was highly variable, ranging from +0.55 to -2.56 g/d for mid-restriction pregnancies and from +0.79 to -3.91 g/d for late-restriction pregnancies. For mid-restriction pregnancies, the number of restriction days was best explained by linear weight change and total weight loss while the number of restriction days in late pregnancy was best explained by linear weight change alone. In late-restriction pregnancies, smaller females had higher daily weight losses. Restrictions did not induce litter-size reduction or growth restriction in those infants that were delivered at term but the size of aborted fetuses suggested that at least some pregnancies lost preterm may have involved impaired intra-uterine growth.

ESTIMATION OF GESTATIONAL AGES IN THE COMMON MARMOSET (CALLITHRIX JACCHUS)FROM PUBLISHED PRENATAL GROWTH CURVES

This report compares estimated gestational ages from published cubic spline curves to gestational ages estimated retrospectively from delivery dates in 28 pregnancies from ten common marmosets (Callithrix jacchus). Both CRL‐ and BPD‐based estimates of gestational age were closely correlated with delivery‐based gestational age estimates. Of the three ultrasound machines used, the one with 16 shades of gray and a sequential linear array overestimated gestational age during early pregnancy, based on CRL measures. Measures from the other two machines (64 or 264 shades of gray; linear sector and annular array or electronic phase array) were similar and resulted in a correlation of the two estimates of gestational age of 0.94 and a mean difference between the two estimates of 0.16 days with 80% of CRL‐based gestational age estimates being within ± 5 days of the delivery‐based estimate. The reliability of BPD‐based estimates of gestational age was strongly related to pregnancy outcome. BPD‐based estimates underestimated gestational age in poor outcome pregnancies (i.e., those in which infants died within 7 days of birth) but not in good outcome pregnancies. The combined CRL‐ and BPD‐based estimates on poor outcome pregnancies suggest that there was less growth in BPD in late gestation for those pregnancies that resulted in nonviable offspring. For good outcome pregnancies, the correlation between BPD‐based and delivery‐based estimates of gestational age was 0.871 and the mean difference between the two estimates was −0.06 days with 83.3% of BPD‐based estimates falling within ± 5 days of delivery‐based estimates.

Ingestion of calcium solutions by common marmosets (Callithrix jacchus)

Callithrix jacchus, the common marmoset, is a small New World primate that feeds on insects, fruit, and gum, and has a high reproductive rate for a primate. Insects are generally a poor source of dietary calcium, while gums may contain significant levels of calcium. Their high reproductive rate also suggests that reproductive female C. jacchus might be susceptible to calcium deficiency. Thus, we hypothesized that common marmosets might find solutions containing calcium to be palatable. We used choice experiments to examine this phenomenon in 14 male and 19 female common marmosets. Animals were presented with identical water bottles containing either deionized water or a calcium lactate solution (either 2% or 4% calcium lactate by weight) and intake was measured. Serum 25‐OH‐vitamin D was monitored in a subset of the animals in the experiment to examine the role of vitamin D in this behavior. Our results demonstrated that C. jacchus can distinguish between plain water and a calcium lactate solution, and that in general they prefer calcium solutions. Although animals with marginal vitamin D status did have strong preferences for calcium solutions, they did not ingest significantly more of the calcium solutions than animals that were vitamin D‐replete. Nulliparous females and males did not differ in the amounts of calcium solutions ingested. Lactating females ingested the greatest volume of the calcium solutions. Am. J. Primatol. 47:255–261, 1999.

Neonatal behavioral scoring of common marmosets (Callithrix jacchus): relation to physical condition and survival

A seven‐task behavioral test was performed on 86 common marmoset (Callithrix jacchus) infants, 24–36 h following birth. This report describes the test outcome and its relation to physical condition and survival of the infants. The percentage of infants receiving a perfect score on a given task ranged from 30.6 (rooting) to 70.6% (grasping). Heavier infants were more likely to have perfect scores for crawling (F=4.20, P=0.044) and infants with a longer knee–heel length tended to be more likely to have a perfect grasping score (F=3.63, P=0.06). While the modal score was a perfect score for most individual tasks, the modal number of total perfect scores that a given infant received was 3–4 and only 4.7% of infants received perfect scores on all seven tasks. These results suggest that this group of behavioral tasks will produce a variable response within a population of neonates. While no individual behavioral score predicted survival during week 1, the number of perfect scores across all tasks was predictive of survival outcome; infants with a higher total number of perfect scores were more likely to survive (F=6.02, P=0.018). When all combinations of tests were compared, the best predictor of survival was outcome on four of the seven tests, all related to motor skills (F=7.46, P=0.009).