Differences in Faecal Nutritional Components in Three Species of Saharan Gazelles on Standard Diets in Relation to Species, Age and Sex

SIMPLE SUMMARY: The study examines how different factors influence the nutritional content of faeces from three gazelle species, with particular interest in the inter-specific factor. Through the contents of nitrogen and fibre, faeces can tell us about their digestive process. The research focuses on 193 captive individuals of three gazelle species and applied Near InfraRed Spectroscopy technology. The results show that different species have varying faecal nutrient levels. Cuvier’s gazelle had lower nitrogen content, suggesting less efficient digestion than other gazelles. Factors like sex and age also played a role, but their effects were not the same for all species. Fibre content, related to diet quality, remained consistent. This study shows that factors affecting faecal nutrients are species-specific. ABSTRACT: Various environmental, individual, and species-specific factors may affect digestive efficiency in wild ruminants. The study of faecal nutritional components is a commonly used technique to understand these effects, assuming that faecal nitrogen and fibre contents reflect the diet’s nutritional quality and digestibility. Recent studies have highlighted the relatively high influence of factors like sex, age, weight or body condition on digestive efficiency. This manuscript is focused on the inter-specific variability in faecal nutritional components under the same feeding regime, using three captive populations of closely related gazelles as model species. Faecal samples from 193 individuals were analysed through Near InfraRed Spectroscopy. Species, sex and age influence on faecal nitrogen and fibres (ADF and NDF) were investigated. We found inter-specific differences in the faecal content of the three studied nutritional components. Cuvier’s gazelle showed lower faecal nitrogen content, suggesting lower digestive efficiency than dorcas and dama gazelles. Sex and age also had a moderate effect, especially in faecal nitrogen, but these effects were not constant across the three studied species. On the contrary, faecal fibres were highly constant (i.e., dependent on diet quality). These results confirm that individual factors affecting faecal nutritional components are also species-specific.