Ochotona Curzoniae Physiological Adaptation To Oxytropis Ochrocephala Toxin And Food-Hoarding Behavior

Ochotona curzoniae is a unique small mammalian herbivore inhabiting the alpine meadow ecosystem in the Qinghai-Tibet plateau.Genus Oxytropis is plant species on the Qinghai-Tibet alpine meadow ecosystem with short growth season from early spring to late autumn.The species contains 10%~ 20% protein,and is one of major summer food items and main haypile ingredient for O.curzoniae.However,the indolizidine alkaloid swainsonine(SW)of oxytropis is toxic and even lethal to many livestocks,as it can inhibit the lysosomal a-mannosidase and Golgi mannosidase.Inhabiting on the meadow with hypotherimia and hypoxemia,O.curzoniae not only has to adapt to the severe environment,but also deals with the plant chemical defense of SW in oxytropis ingested.Therefore,in the long process of natural selection,O.curzoniae has evolved a wide range of behavioral strategies and physiological mechanisms to mitigate the negaitive effects of PSMs.The purpose of this study was to explore the O.curzoniae's digestive strategies and hepatic cytochrome P450 exposed to SW by feeding O.ochrocephala and SW crude extract.In addition,we also studied the nutrients dynamic changes of the O.curzoniae haypile during stored period.The hypotheses we tested were:(1)O.curzoniae may increase the intake and improve digestibility,and(2)when exposing O.curzoniae in O.ochrocephala with the rang of ecological concentration,O.curzoniae has a certain degree of tolerance to oxytropis SW,and its liver cytochrome P450 content may have compensatory adjustments responsibe for with the increase of diet SW does and exposed time.In addition,we predicted that the oxytropis containing toxic swainsonine and / or other PSMs,can slow the rate of degradation of plants from the haypiless,and preserve the nutritional value of haypile during storage.The results of the study were as follows:(1)The result of which the effect of O.ochrocephala on O.curzoniae digestibility showed plateau pikas improved food intake,absorption and digestibility of neutral detergent fiber exposed O.ochrocephala.This result supported our hypothesis that the oxytropis can improve plateau pikas digestibility.(2)The level of CYP450 in liver of O.curzoniae ingested SW decreased initially,and the inhibitory effect of the toxin on CYP450 level was overcome over time and the CYP450 level even increased.These results may suggest that O.curzoniae is capable of adjusting its production of CYP450 enzymes when the enzymes are needed for SW detoxification.(3)The biomass,protein and neutral detergent fiber of haypiles with O.ochrocephala preserved during storage were retained better compared haypiles without O.ochrocephala.At the end of storage,the biomass and protein for return were respectively 15.20%,35.86% higher in the oxytropis-added group than that in free-oxytropis group.This result supported the hypothesis that O.ochrocephala could enhance the preservation of nutrient of haypiles during storage.