Relationships Between Food Composition And Plant Nutrition, Secondary Metabolites As Another, Of Red Deer (Cervus Canadensis Xanthopygus) In Muling, Heilongjiang Province, China

Nutritional ecology of large herbivores concerns how animals forage on plants to meet nutritional requirements and avoid plant secondary metabolites to resist phytochemical defenses simultaneously,both of which related to the successful acclimatization of animals directly.Existing theories related to nutritional ecology constrained research on how one or several(types)of nutrient(s)or non-nutrient(s)influences on animal feeding and nutritional strategies and considered the target(non-)nutrient(s)as the most influential ecological factor of animals’ survival.Moreover,the results are mostly based on controlled experiments,but nutritional ecological processes in wildlife are more complex.In this study,we selected a red deer(Cervus canadensis xanthopygus)population distributing in Heilongjiang Muling National Nature Reserve,northeast China to investigate the relationship between food composition and nutrients,plant secondary metabolites as another.We investigated different food composition patterns within the population and studied the relationship between food composition and secondary metabolites in terms of both food nutrition and secondary metabolites.This study aims at providing comprehensive data on the nutritional ecological process of wild large ungulates in high latitude zones during winter time intercept,and a basis for addressing potential nutritional limitations of populations and conservation of red deer.92 fecal samples were collected from the Heilongjiang Muling National Nature Reserve,in winter of 2020 and 2021.Food composition,food nutrients,and secondary metabolite contents of red deer were determined by fecal micro-histological,phytonutrient determination,and widely targeted metabolome respectively.Statistical methods including k-means clustering,principal component analysis and Mantel test were used to investigate the food composition pattern,differences in nutrient content of foraged plants and secondary metabolites,and factors influencing the food composition pattern within population in winter.Main results of the study are as follows.1.Food items of the red deer population was relatively stable during the winter sampling period,and red deer mainly foraged on 31 plant species.Winter food composition of red deer population was mainly woody plants,with less herbaceous plants.Deciduous trees were the staple food of red deer,and a high proportion of coniferous trees were also taken.K-means clustering results indicated that there were different food composition patterns within the red deer population.Fecal micro-histological analysis from both winters showed different food composition patterns within the population with red deer Taxus cuspidata,Acer barbinerve,and Corylus mandshurica as the main food items,respectively.2.Average contents of crude fat,ash,hemicellulose and cellulose in the nutrient content of the plants taken by the deer in different winter sampling periods showed significant inter annual difference.Coniferous had the highest crude protein and crude fat contents,and higher cellulose and hemicellulose contents,which were the types of plants foraged more by deer in winter.Deciduous trees had a balanced content of crude protein,crude fat,ash,and hemicellulose,and were the main food type chosen by the deer in winter.Meanwhile,there are many types of secondary metabolites in plants,with 638 metabolites measured in 11 plants in 2020 and 669 metabolites measured in 19 plants in 2021.Secondary metabolites also differed significantly across plant classes,with 187 and 208 differential metabolites in 2020 in coniferous trees compared with broadleaf trees and shrubs,and 208 differential metabolites between broadleaf trees and shrubs,respectively;and 234 and 279 differential metabolites in 2021 in coniferous trees compared with broadleaf trees and shrubs,and 132 differential metabolites.3.Effect of each nutrients and non-nutrients on food composition pattern within red deer population showed that the food composition of red deer in winter is influenced by a variety of factors rather than the result of a single factor,and when the animal’s intake of a certain substance reaches satisfaction,the content of other(non-)nutrients may become a limiting factor affecting its food composition.Nutrients such as crude protein,crude fat,fiber-like substances and secondary metabolites such as flavonoids,phenolic acids and tannins in plants are the main factors influencing the formation of different food composition patterns within population.Inequality of influences of(non-)nutrients on food composition pattern exists at different time intercept,within population and persuasive across nutritional ecological process.