Environmental, morphophysiological, and individual factors affecting faecal indices: application of near-infrared reflectance spectroscopy to nutritional studies

Ing. Stipan Čupić

Disertační práce

Abstract:

Understanding the dietary patterns of free-ranging ungulates is of fundamental importance for wildlife management and conservation due to the influence of diet on the populations' well-being, health, and performance. Consequently, animals’ dietary efficiency determines the overall health and stability of forests and other habitats that they consist of, and very often, as the key modifying component. Animal faeces, particularly their nitrogen and fibre constituents, are the most extensively used organic materials/proxies in the nutritional ecology of ungulate species since they often display a positive correlation with the same dietary ones, therefore, allowing calculation of the animal’s digestive efficiency. Knowing the latter at a desired place and time allows wildlife managers and conservationists to make proper decisions and achieve goals consistent with stable and balanced animal populations and their surrounding habitats. The accuracy of interpretation of this critical information can be compromised by a wide range of environmental, inter-specific (morphophysiological), intra-specific (animal/individual-specific) factors and the interactions among them. Animal dietary patterns may now be studied in unprecedented detail thanks to technologically advanced tools, such as near-infrared reflectance spectroscopy (NIRS). This thesis aimed to assess the influence of intra-specific, basic environmental, and intra-specific factors on animal faecal constituents such as faecal nitrogen (fN) and faecal acid fibres (fADF and fNDF). Furthermore, the goal was to test the predictability power and accuracy of the NIRS technique for such research, define the advantages and limitations, and avoid future equivocal results and interpretations, potentially leading to wrong management and conservation decisions. The work was divided into two imaginary parts. First, the captive animals were used to assess the effects of sex, age, reproductive status, body mass, and body condition (intra-specific; red deer was the model species due to its pronounced sexually dimorphic characteristics), effects of season and pasture availability, and morphophysiological characteristics (closely related mhorr, dama, and Cuvier’s gazelle) for which also effects of sex and age were assessed. After assessing the impact of these factors under the controlled environments, the aim was to conduct two case studies with free-ranging populations of overlapping roe and red deer populations in the Czech Republic and free-ranging Andean bear in Ecuador, as examples of uncontrolled conditions. Even in a controlled environment with healthy animals and similar feeding sources, red deer showed relatively high variability in the analysed faecal nutrients, sometimes above 25%. All studied individual factors, season, and pasture availability significantly explained such variability. Morphophysiological factors and age significantly affected fN and, to a smaller extent, faecal fibres, while the effect of sex varied depending on species (except Cuvier’s gazelle). NIRS generally showed satisfactory predictive power and the potential to answer important ecological questions relevant to wild population management and conservation. Still, shortcomings can lead to wrong interpretations and conclusions, as in the case of free-ranging roe and red deer, therefore with the possibility of advancement. Before conducting research in the wild, it is strongly advisable to previously validate the study on captive populations or carefully plan the research, not setting up too ambitious goals. The predictive power, and thus the applicability of NIRS in this kind of research, could be elevated just by adding analysis of N bound to ADF in faecal, which would allow calculation of metabolic faecal nitrogen (MFN).

Keywords

red deer, ungulates, NIRS, gazelles, nutrition

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 25. 4. 2024

Obhajoba závěrečné práce

• Obhajoba proběhla 21. 3. 2023
• Vedoucí: doc. Ing. Vlastimil Hart, Ph.D.

Česká zemědělská univerzita v Praze

Fakulta lesnická a dřevařská

Doktorský studijní program / obor:
Forestry Engineering / Forest Protection and Game Management