Determining overweight and underweight with a new weight-for-height index in captive group-housed macaques

Abstract

Housing primates in naturalistic groups provides social benefits relative to solitary housing. However, food intake may vary across individuals, possibly resulting in overweight and underweight individuals. Information on relative adiposity (the amount of fat tissue relative to body weight) is needed to monitor overweight and underweight of group-housed individuals. However, the upper and lower relative adiposity boundaries are currently only known for macaques living solitarily in small cages. We determined the best measure of relative adiposity and explored the boundaries of overweight and underweight to investigate their incidence in group-housed adult male and female rhesus macaques and long-tailed macaques living in spacious enclosures at the Biomedical Primate Research Centre (BPRC), the Netherlands. During yearly health checks different relative adiposity measures were obtained. For long-tailed macaques, comparable data on founder and wild animals were also available. Weight-for-height indices (WHI) with height to the power of 3.0 (WHI3.0) for rhesus macaques and 2.7 (WHI2.7) for long-tailed macaques were optimally independent of height and were highly correlated with other relative adiposity measures. The boundary for overweight was similar in group-housed and solitary-housed macaques. A lower boundary for underweight, based on 2% body fat similar to wild primates, gave a better estimate for underweight in group-housed macaques. We propose that for captive group-housed rhesus macaques relative adiposity should range between 42 and 67 (WHI3.0) and for long-tailed macaques between 39 and 62 (WHI2.7). The majority of group-housed macaques in this facility have a normal relative adiposity, a considerable proportion (17-23%) is overweight, and a few (0-3%) are underweight.

Keywords: BMI; Macaca; adiposity; body mass index; colony management.

Figure 1

WHI3.0 plotted against height for adult female (black circles) and male (black triangles) rhesus macaques currently housed at the BPRC. WHI3.0 was optimally independent of height in females (black solid line), whereas there was a nonsignificant negative relationship between WHI3.0 and height in males (black dashed line). The dark gray bar represents the proposed relative adiposity boundaries by Raman et al. (2005), which correspond to 52 < WHI3.0 < 67. The light gray bar indicates the new lower boundary based on 2% body fat, similar to wild primates. BPRC, Biomedical Primate Research Centre; WHI, weight‐for‐height indices

Figure 2

WHI2.7 plotted against height for different adult long‐tailed macaque samples. First panel: Current BPRC females (black circles) and current BPRC males (black triangles); second panel: founder females (dark gray circles) and founder males (dark gray triangles); and third panel: wild females (light gray circles) and wild males (light gray triangles). The dark gray bar represents the proposed relative adiposity boundaries by Raman et al. (2005), which correspond to 48 < WHI2.7 < 62. The light gray bar indicates the new lower boundary based on 2% body fat, similar to wild primates. WHI2.7 values of different sex‐population groups were generally independent of height. WHI, weight‐for‐height indices

Figure 3

Relationship between body condition score and (a) WHI3.0 (rhesus macaque females) and (b) WHI2.7 (long‐tailed macaque females) at the BPRC. The dark gray bar represents the proposed relative adiposity boundaries by Raman et al. (2005), which are 52 < WHI3.0 < 67 in rhesus macaques and 48 < WHI2.7 < 62 in long‐tailed macaques. The light gray bar indicates the new lower boundary based on 2% body fat levels in the wild, which corresponds to WHI3.0 = 42 (rhesus macaques) and WHI2.7 = 39 (long‐tailed macaques). The y‐axes are differently scaled. BPRC, Biomedical Primate Research Centre; WHI, weight‐for‐height indices