Maternal factors affecting reproduction in a breeding colony of cynomolgus macaques (Macaca fascicularis)

A breeding colony of cynomolgus macaques (Macaca fascicularis), composed of imported and colony-born animals and established for 9 years, was evaluated for maternal factors associated with reproductive failure. The factors evaluated included age, gravidity, parity, origin, previous stillbirths, clinical incidents and type of housing. The effects of each factor on pregnancy rate (PR), stillbirth rate (SR), infant mortality rate (IMR) and pregnancy success (PS) were evaluated. The overall colony rates were: PR = 53%, SR = 22%, IMR = 22%, and PS = 60%. Neonatal death rate for the group was 12%. Pregnancy rate was most affected by maternal factors. Clinical incidents occurring during pregnancy were associated with a significant increase in the stillbirth rate, but did not affect infant mortality rate. Maternal age did not affect any of the measures of reproductive output. Pregnancy rate peaked at 6-8 years of age and decreased thereafter, while pregnancy success peaked at 9-11 years of age. Gravidity and parity had a positive linear relationship with pregnancy rate.