Refinement of rearing practices in marmosets

Improvements in the diet of common marmosets bred for
research has led to an increase in litter size from two to
three or even four infants. This increase is associated with
high infant mortality, birth complications and rearing
practices that involve temporarily removing one or more
infants from the family unit, which is known to affect
behaviour and physiology. This project will compare the survival, development, behaviour and welfare of marmosets reared under different husbandry practices to
identify the best breeding and rearing methods. The
findings could have far-reaching implications for the
welfare of marmosets in breeding and research facilities,
and for the reliability of the marmoset as a model in
research and testing."

The project will investigate how to refine breeding and rearing to promote best practice for welfare and research in the common marmoset (Callithrix jacchus). This small monkey is the most frequently used New World primate in European laboratories, primarily for toxicology. There are considerable welfare problems associated with breeding marmosets, including high infant mortality from large litter sizes (twins are the norm in the wild), birth complications, and rearing practices that often necessitate early deprivation from the family which is known to have adverse effects on behaviour and physiology. Studies will be conducted at a breeding facility which supplies marmosets to laboratories. Carefully designed experiments will compare infant development, family interactions, response to routine stressors, weight gain, learning and motivation in marmosets born to litters of different sizes and reared in different conditions. These conditions include (a) marmoset-reared twins (control) (b) marmoset-reared infants from triplets (c) rotationally-reared triplets (d) foster-reared triplets (e) human-reared infants from triplets and (f) marmoset-reared singletons. The findings, combined with back record analyses will determine factors affecting litter size, dam mortality and best rearing practices for welfare when litters exceed two. Should, as anticipated, the results demonstrate that marmoset-reared twins have the best welfare, the lowest mortality, fewest birth complications and produce the best models, then evidenced-based recommendations to husbandry to promote twin births will be trialled. As heavier dams produce larger litters, this may include maintaining dams at weights similar to wild counterparts to increase the incidence of twins births. When litters exceed two, another Refinement may be to train marmosets to allow care staff to provide supplementary food for carried infants to obviate separation. The findings should have far-reaching implications for quality of life of marmosets in breeding facilities, and for the reliability of the marmoset as a model in research and testing.