Estimating body weight of pigs from posture analysis using a depth camera.

A noninvasive method for estimating the body weight (BW) of a pig considering its posture using a low-cost depth camera (Kinect v2) was proposed. A total of 150 pigs were used, and 738 depth images (point clouds) were obtained for them. The pig "volume" was calculated from the pig point cloud, and it was found to have a very high correlation to BW. To evaluate the posture of a pig quantitatively, seven posture angles were calculated based on the "spine" extracted from a pig point cloud. We found the posture angles representing the height of the head position correlated with the accuracy of BW estimation using the "volume." Based on this finding, we proposed an "adjusted volume," which was adjusted based on the relationship between the posture angles and the estimation error. The BW of pigs was estimated using the simple regression model with the "adjusted volume," and the MAPE and RMSPE were 4.87% and 6.13%, respectively. The accuracy of the suggested model was similar to that of the volume-based estimation models of other studies that used only data with an appropriate pig posture for BW estimation.

Assessment of nest building and social interaction behavior in mice exposed to acute social defeat stress using a three-dimensional depth camera.

Nest building is an instinctive behavior toward protection from predators, body temperature regulation, and courtship. Previously, we discovered that acute and chronic social defeat stress suppresses the onset of nest-building behavior in male mice (C57BL/6J). Here, we analyzed nest building and other behavioral deficits induced by acute social defeat stress (ASDS). We utilized a customized cage and specifically developed observational programs for nest building, social avoidance, and other behaviors using an infrared depth camera to acquire three-dimensional (3D) data of animal behavior (Negura system). We determined the volume of nesting materials from these 3D depth images. Mice exposed to ASDS showed increased spontaneous activities, decreased rearing, and delayed nest building; however, nest-building activity was gradually recovered during the dark period of the 24 hr observation interval. At the endpoint following 24 hr, the ASDS and control groups showed no differences in nest volumes. Furthermore, we observed the time courses of both nest building and social avoidance behaviors and their relationship using the Negura system. Our data demonstrated a weak positive correlation between nest-building delay and social avoidance in ASDS mice. The Negura system can observe various behaviors that reflect the effects of social defeat stress.

The acute social defeat stress and nest-building test paradigm: A potential new method to screen drugs for depressive-like symptoms.

Psychosocial stress can cause mental conditions such as depression in humans. To develop drug therapies for the treatment of depression, it is necessary to use animal models of depression to screen drug candidates that exhibit anti-depressive effects. Unfortunately, the present methods of drug screening for antidepressants, the forced-swim test and tail-suspension test, are limiting factors in drug discovery because they are not based on the constructive validity of objective phenotypes in depression. Previously, we discovered that the onset of nest building is severely delayed in mice exposed to subchronic mild social defeat stress (sCSDS). Therefore, a novel paradigm combining acute social defeat stress (ASDS) and the nest-building test (SNB) were established for the efficient screening of drugs for depressive-like symptoms. Since ASDS severely delayed the nest-building process as shown in chronically social defeated mice, we sought to rescue the delayed nest-building behavior in ASDS mice. Injecting a specific serotonin 2a receptor antagonist (SR-46349B), the nest-building deficit exhibited by ASDS mice was partially rescued. On the other hand, a selective serotonin reuptake inhibitor (fluoxetine) did not rescue the nest-building deficit in ASDS mice. Therefore, we conclude that the SNB paradigm is an another potential behavioral method for screening drugs for depressive-like symptoms including attention deficit, anxiety, low locomotion, and decreased motivation.

Murine Depression Model and its Potential Applications for Discovering Foods and Farm Products with Antidepressant-Like Effects.

Advanced societies face increased health problems related to various stresses. Chronic psychological stress is a major risk factor for psychiatric disorders such as depression. Although therapeutic agents reduce several symptoms of depression, most have side effects in a broad range of the population. Furthermore, some victims of depression do not show significant improvement with any drugs, so alternative approaches are needed. Good dietary habits may potentially reduce depressive symptoms, but there is little scientific evidence thus far. Murine depression models are useful to test nutritional approaches in vivo. Our model mice subjected to a subchronic mild social defeat stress (sCSDS) paradigm show several alterations in physiological parameters and social behavior. These stress-induced symptoms in sCSDS mice can be used as cues to identify antidepressant-like natural resources including foods and farm products. We previously discovered that sCSDS mice show more vulnerability to social stress by changing dietary condition. In addition, we developed a more objective system for analyzing mouse behavior using a 3D depth-sensing camera to understand relationships between diet and behavior. The combination of sCSDS mice with 3D behavioral analysis is a powerful method for screening ingredients in foods and farm products for antidepressant-like effects.

Subchronic and mild social defeat stress alter mouse nest building behavior.

Behavioral and physiological evaluations of animal models of depression are essential to thoroughly understand the mechanisms of depression in humans. Various models have been developed and characterized, and the socially defeated mouse has been widely used for studying depression. Here, we developed and characterized a mouse model of social aversion using a subchronic and mild social defeat stress (sCSDS) paradigm. Compared to control mice, sCSDS mice showed significantly increased body weight gain, water intake, and social aversion to dominant mice on the social interaction test. We observed nest building behavior in sCSDS mice using the pressed cotton as a nest material. Although sCSDS mice eventually successfully built nests, the onset of nest building was severely delayed compared to control mice. The underlying mechanism of this significant delay in nest building by sCSDS mice is unclear. However, our results demonstrate that nest building evaluation is a simple and useful assay for understanding behavior in socially defeated mice and screening drugs such as antidepressants.

Strain differences in temporal changes of nesting behaviors in C57BL/6N, DBA/2N, and their F1 hybrid mice assessed by a three-dimensional monitoring system.

Nest building is one of the innate behaviors that are widely observed throughout the animal kingdom. Previous studies have reported specific brain regions and genetic loci associated with nest building in mice. These studies mainly evaluated the nest structure, without observing the nesting process. In this study, we evaluated the effects of strain and learning on the nesting process of mice using a 3D depth camera. To determine the quality of the nest structure, a conventional scoring method, Deacon scores 1-5, was applied to the recorded depth images. The final score of the nest, latency to start nesting behavior, and latencies to reach Deacon scores 3-5, were determined using three genetically different mouse strains-C57BL/6NCrl (B6), DBA/2NCrlCrlj (DBA), and B6D2F1/Crl (B6D2F1). The final score of the DBA nest was significantly lower than that of the B6D2F1 nest, and DBA mice showed significantly longer latency to start nest building than the other two strains in the first trial. By observing the time course of nest building, we confirmed that DBA mice took significantly longer to build their nests than B6 and B6D2F1 mice. Although we did not find any significant differences between DBA and B6 mice in the final assessment of the nest based on the Deacon method, overnight monitoring of the nesting behavior using a 3D depth camera could elucidate the clear differences in the amount of time spent nesting between DBA and B6 mice. In addition, the learning effect was more evident in DBA mice than it was in B6 in terms of latencies to reach Deacon score 3-5 in five repeated trials. DBA mice showed a gradual decrease in latency to build, whereas nesting behaviors of B6 mice were relatively consistent throughout the five trials. Therefore, our 3D depth image method gives higher resolution and structural information regarding the nesting process in mice. Future genetic analyses using the 3D assessment system will provide novel insights into the complex genetic basis for nesting and other behaviors in animals.

Assessing nest-building behavior of mice using a 3D depth camera.

We developed a novel method to evaluate the nest-building behavior of mice using an inexpensive depth camera. The depth camera clearly captured nest-building behavior. Using three-dimensional information from the depth camera, we obtained objective features for assessing nest-building behavior, including "volume," "radius," and "mean height". The "volume" represents the change in volume of the nesting material, a pressed cotton square that a mouse shreds and untangles in order to build its nest. During the nest-building process, the total volume of cotton fragments is increased. The "radius" refers to the radius of the circle enclosing the fragments of cotton. It describes the extent of nesting material dispersion. The "radius" averaged approximately 60mm when a nest was built. The "mean height" represents the change in the mean height of objects. If the nest walls were high, the "mean height" was also high. These features provided us with useful information for assessment of nest-building behavior, similar to conventional methods for the assessment of nest building. However, using the novel method, we found that JF1 mice built nests with higher walls than B6 mice, and B6 mice built nests faster than JF1 mice. Thus, our novel method can evaluate the differences in nest-building behavior that cannot be detected or quantified by conventional methods. In future studies, we will evaluate nest-building behaviors of genetically modified, as well as several inbred, strains of mice, with several nesting materials.