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Nursery rearing of infant monkeys (Macaca fascicularis) for toxicity studies
Insights
Infant cynomolgus monkeys (Macaca fascicularis) exhibit distinct growth patterns and physiological changes in early life. Early social development and appropriate rearing environments are crucial for preventing behavioral abnormalities.
Area of Science:
- Primate developmental biology
- Comparative physiology
- Behavioral neuroscience
Background:
- Understanding early life development in non-human primates is essential for biomedical research and conservation efforts.
- Cynomolgus monkeys (Macaca fascicularis) serve as a valuable model for studying primate growth, physiology, and behavior.
Purpose of the Study:
- To characterize the growth, caloric intake, hematological parameters, and behavioral development of infant cynomolgus monkeys from birth to approximately 6 weeks of age.
- To establish normative data for early development in this species.
Main Methods:
- Longitudinal monitoring of body weight and food intake in infant male and female cynomolgus monkeys.
- Analysis of hematological parameters including erythrocyte counts, packed cell volume, and hemoglobin.
- Observation and documentation of behavioral development, including social interactions and temperament.
Main Results:
- Infant males showed a higher average birth weight and growth rate compared to females.
- Caloric intake per kilogram body weight peaked early and subsequently declined, with sex-specific differences observed.
- Hematological values (erythrocytes, packed cell volume, hemoglobin) decreased initially and then stabilized; lymphocyte counts increased while neutrophils decreased.
- Early signs of temperament and aggression were noted, with social order development beginning around 30-40 days; isolation-reared behavioral abnormalities were absent in this group.
Conclusions:
- Infant cynomolgus monkeys display predictable patterns of growth, metabolic adaptation, and physiological maturation in the early postnatal period.
- The observed behavioral development, including early social structuring, suggests that adequate rearing conditions support normal development and mitigate common abnormalities.
Abstract:
At birth, nine infant male cynomolgus monkeys (Macaca fascicularis) weighed an average of 402 g and 16 infant female cynomolgus monkeys weighed an average of 362 g. Both female and male infants last 15-20 g by the fourth day after birth. Female and male infants showed a growth rate of approximately 4 and 5 g body wt/day, respectively, from 4 to 150 days of age. Caloric intake increased from approximately 140 cal/gkg body weight/day in both females and males on the first day after birth to peak values of 325 and 290 cal/kg body weight/day in females and males, respectively, and subsequently declined to about 200 cal/kg/day in males and 250 cal/kg/day for females. Total calories consumed per day increased from 53 cal/day in females and 68 cal/day in males to approximately 200 cal/day after 60 days of age in both females and males. Erythrocyte counts, packed cell volume, and hemoglobin values decreased from birth to 2 weeks of age, then stabilized. An increase in lymphocyte count, with a concomitant decrease in mature neutrophils, was observed from birth to 6 weeks of age. "Temper fits" and certain aggressive behavioral signs were observed as early as 3-4 days after birth, and infants began to develop social orders as early as the 30-40th day. Behavioral abnormalities frequently seen in infants reared in isolation were not observed.