Emotions are an integral part of animal welfare.Facial expressions are increasingly used as a non-invasive method for assessing the emotional state of animals.Dogs(Canis familiaris)are closely related to humans,and facial expressions are crucial for interspecies communication and emotional expression.This paper reviews the neurobiological mechanisms of facial expressions and the anatomical structure of the facial muscles and their evolution in dogs,the analogy between dog and human facial expressions,and the expression of various parts of the dog's face under different emotions.These studies demonstrate that dog's facial expressions can be used as a potential indicator of animal welfare,and that dogs can be used as a model animal for studying interspecies facial emotional communication.The use of dog's facial expressions to assess emotions will aid multidisciplinary research,including in the fields of neuroscience,psychopharmacology,animal behavior,and animal welfare.

Emotions are an integral part of animal welfare.Facial expressions are increasingly used as a non-invasive method for assessing the emotional state of animals.Dogs(Canis familiaris)are closely related to humans,and facial expressions are crucial for interspecies communication and emotional expression.This paper reviews the neurobiological mechanisms of facial expressions and the anatomical structure of the facial muscles and their evolution in dogs,the analogy between dog and human facial expressions,and the expression of various parts of the dog's face under different emotions.These studies demonstrate that dog's facial expressions can be used as a potential indicator of animal welfare,and that dogs can be used as a model animal for studying interspecies facial emotional communication.The use of dog's facial expressions to assess emotions will aid multidisciplinary research,including in the fields of neuroscience,psychopharmacology,animal behavior,and animal welfare.

Objective To establish an osteoporosis model in tree shrews by bilateral ovariectomy.Methods One hundred healthy 6-24 month old female tree shrews were used in this study.The diagnosis and treatment of osteoporo-sis in the model tree shrews was assessed according to the Interpretation of the Clinical Practice Guideines for Primary Oste-oporosis 2011 released by the Chinese Medical Association of Osteoporosis and Bone Mineral Salt Disease Branch.① Ac-cording to the human natural life span, sexual maturation time and peak bone mineral density ( PBMD) and the tree shrew natural life span and sexual maturation time, we estimated the PBMD of tree shrew in the age of months.Six 6-, 12-, 18-and 24-month old tree shrews in each group were randomly taken for measurement of BMD, and compared the differences between groups to verify the PBMD age of tree shrews.②We chose 62 6-month old tree shrews from the rest of tree shrews to measure their BMD to determine the mean and standard deviation of BMD.Then we divided them into study group ( n =32) and control group (n =30).Bilateral ovariectomy was performed in the study group, while omentectomy was done in the control group.BMD was measured at 3, 6, 9, 12 months after the surgery, 6 animals from each group.The animals which met the criteria of guideline were taken for pathological examination.Results ①The PBMD of 6-, 12-, 18-, 24-month old tree shrews was 0.138 ±0.012, 0.143 ±0.010, 0.141 ±0.009, and 0.139 ±0.009) g/cm2 , respectively, showing no significant differences among them (P>0.05).②The mean PBMD of the tree shrews was 0.143 ±0.016 g/cm2 .③In the model groups, the number of tree shrews whose BMD met the criteria of guideline was 0, 5, 4, 5, respec-tively.The pathological examination of the proximal tibia from the model group showed sparse and some disrupted trabecu-lae and enlarged inter-trabecular space.In the control group, the tibia tissues showed normal histology of bone structure and no one tree shrew showed a BMD value which met the criteria of diagnosis of osteoporosis.Conclusions An osteopo-rosis model in tree shrews can be established at 6 months after bilateral ovariectomy, showing similar manifestation of osteo-porosis in postmenopausal women.The success rate of this modeling method is high and the model is stable.