Prospective Study on the Excretion of Mucous Stools and its Association with Age, Gender, and Feces Output in Captive Giant Pandas

SIMPLE SUMMARY: Captive pandas may excrete mucous stools, which are often accompanied by discomfort and decreased activity. Thus, the excretion of mucous stools is a welfare concern for pandas kept in zoos. In this study, we documented the frequency of mucous excretions and the daily feces weights of 18 giant pandas (Ailuropoda melanoleuca) in the Beijing Zoo from April 2003 to June 2017. We also explored possible associations between the excretion of mucous stools and the pandas’ gender, age, and feces output. During the study, 900 cases of mucous excretion occurred over 32,856 observation days. The frequency of mucous excretion was negatively correlated with the feces output and positively correlated with the pandas’ age. No correlation with gender was found. Moreover, the mean frequency of mucus occurrence showed monthly changes, with one significant peak in October, and the time series analyses showed that the time (month) change imposed the strongest negative effect on fecal output, while the biggest effects on fecal output and mucus excretion both occurred in August (seasonal factors were −2.261 and 0.0126, respectively). Our findings not only add to the literature concerning pandas but are also helpful for enhancing their welfare. Further studies addressing the underlying mechanisms for the occurrence of mucus in captive pandas are needed. ABSTRACT: The giant panda (Ailuropoda melanoleuca) has evolved a large number of mucous glands in the intestinal lining to adapt to the digestion of high-fiber foods. However, in captive pandas, excessive mucus might form a mass and then be eliminated, which is often accompanied by discomfort and decreased activity. This event is called ‘mucous excretion’. The causes of mucus excretions in captive pandas, however, remain unknown. The aims of this study were to document the occurrence of mucus excretion and to investigate its possible associations with pandas’ age, gender, and feces output. Eighteen giant pandas were studied at the Beijing Zoo from April 2003 to June 2017, and a total of 900 occurrences of mucous excretion and 32,856 daily defecation outputs in weight were recorded. The likelihood of mucous excretion occurrence decreased by 11.34% for each 1 kg of fecal output (Z = −4.12, p < 0.0001), while it increased by 5.89% per year of age (Z = 4.02, p < 0.0001). However, individual differences in gender had no significant effect on the mucous occurrence (Z = −0.75, p = 0.4508). A monthly change in mucus occurrence was also found. The mean frequency of mucus occurrence was significantly higher in October. In August, time (month) change showed the biggest negative influence on feces output but the biggest positive influence on mucus excretion (seasonal factors were −2.261 and 0.0126, respectively). Our results documented the occurrence of mucous excretions and confirmed their possible associations with the pandas’ age and fecal output based on a 15-year prospective study. This study not only adds to our knowledge of panda physiology but also suggests the need for further studies examining the causes of the excretion of mucous stools in captive pandas. Reducing the incidence of mucous excretion would promote ex situ conservation and enhance panda welfare.