动物造模 z-bo 2020-09-08 637

　　Introduction: Environmental enrichment can meet the behavioral needs of pigs to explore and forage, and help animals adapt to the environment. Pigs raised in barren or abundant environments behave differently. Pigs raised in barren environments are less active, explore less, and show less play behavior. In addition, there are differences in their diversity of behaviors, the development of verbal manipulation behaviors against their peers, the degree of aggression in social interactions, and their physiological responses to stress. Living in a barren environment is very stressful for pigs. At the time of slaughter, pigs raised in a barren environment had higher adrenal gland weight, presumably due to chronic activation of the hypothalamic-pituitary-adrenal (HPA) axis. It has been found that activation of the HPA axis increases the release of cortisol from the adrenal glands. However, recent studies have found that chronic stress can also cause low cortisol. Enriched pigs have a higher baseline cortisol concentration at 22 weeks of age. The hippocampus plays an important role in the stress response. The hippocampus contains a high concentration of glucocorticoid receptors, which are responsible for the negative feedback regulation of the HPA axis to restore allogeneic hyperplasia. In addition, the hippocampus is also involved in space navigation and long-term memory. Stress may have a negative impact on hippocampal function. In the eight-arm radial maze, the foraging behavior of pigs under different stress conditions was studied. They found that even slight pressure can damage the pig’s spatial performance. Environmental enrichment can improve cognitive function. Some rodent studies have shown that the abundance of treadmills, climbing materials and toys can lead to better spatial learning performance. This effect may be mediated by the hippocampus, because enrichment also produces hippocampal changes, such as stimulating neurogenesis in the dentate gyrus. The purpose of this study is to investigate the cognitive performance of pigs raised in barren or rich environments after weaning. The pig evaluates its spatial learning and memory ability in the space board identification task. This task, the hidden food reward, acts as an appetite stimulus, and the stimulating behavior is similar to that of naturally foraging pigs. Beginning at 11 weeks of age, they received two holographic trainings a day, and performed a total of 40 acquisition tests, followed by 20 tests to reverse the initial structure of the bait hole. The enrichment we use is more refined than previous studies, where enrichment only affects working memory. We hypothesize that pigs from a rich environment will perform better in working memory and reference memory than pigs in a barren environment. At the end of the study, their salivary cortisol levels indicate that the environment is poor. The pig will experience more stress.

　　Animals: Two days before weaning, 20 healthy piglets were selected from ten different litters. Choose the two female piglets closest to the average weight from the ten litters. . In each litter of piglets, one of them is randomly assigned to a barren environment, and the other is assigned to a rich environment. At 4 weeks of age, the animals were weaned and transferred to the laboratory. Ten animals under each condition were housed together. The two environments (barren and rich) are located side by side under the stable natural ventilation and natural light from large skylights. The two groups of animals cannot see, but can hear and smell each other. Record the stable temperature every day, the temperature range is between 8℃ and 20℃. The radio broadcasts 12 hours of popular music from the radio every day between 7:00 and 19:00. The barren environment is a concrete floor, 400×500 cm. It has a 130 360-centimeter pigsty with a rubber mattress, two heating lamps, a rubber bite bar, and a drinking and feeding place. The enriched environment is twice as large as the barren environment, with an area of 850×530cm and a rooting area of 360×270cm, full of peat. Add new peat (150 L) every week. A layer of straw bedding is spread on the concrete floor. Add fresh straw every day. In addition, one of four different toys is provided-sticks, balls, jute bags and rope-which change randomly every day. There is a straw pig house, two warm lamps, two drinking places, one feeding place and two rubber biting rods. Thereafter, in order to increase the motivation for finding the hidden bait in the holographic board task, the pigs were fed 1/3 of the daily food at about 7:30 in the morning before the test, and the remaining 2/3 of the food was fed to the pigs every day at about 16:00 after the test.

　　Experimental area and cardboard device: Enviromentally enriched and barren pig houses, pig houses used as waiting areas before the test, and test equipment are all located in the research room and connected by corridors. During the test, pigs enter the waiting area first. The maximum waiting time for the last pig in the experimental group is 45 minutes, which is reduced to 20 minutes during the experiment. When testing environmentally enriched pigs, provide different enrichment toys-sticks, balls, jute bags and ropes in the waiting pigsty. The pigs were then brought individually into the test device. During the test, in the holographic board device, a pig could hear and smell the same group of companions and pigs in other groups, but could not see it. The test equipment is a cognitive holographic panel specially built for pigs. Plate 535 × 535 cm. It has a composite of blue and gray slats, 80 cm high wall. The entire test device is 30 cm high above the ground. The test site has a 4×4 food bowl matrix (the distance between the bowls is 95 cm, and the space between the wall and the bowl is 73 cm). Each food bowl has a fake bottom, and three M&Ms (coated chocolate candies) are placed on the bottom to control the flavor of the bait. These flavors are emitted from the hole, which prevents the pig from positioning the bait bowl based on the reward. Change M&M every day. Prevent pigs from locating the reward food bowls, each bowl is covered with a red synthetic ball. Pigs have to use their noses to lift the ball to reach and eat the food. When the pig retracts its head, the ball returns to its original position, covering the food bowl again.

　　Habituation and behavior test: The experiment was carried out within 12 weeks. After weaning at 4 weeks of age, the pigs were allowed to get used to their new companions and environment. For the first 5 days, the pigs were left undisturbed in their house. Then the pigs in each barn gradually adapt to their testers, test rooms and test equipment. Acclimation takes 3 weeks, 30 minutes twice a day. During the training, the pigs are free to stay with the trainer. In the beginning, the breeder fed the pigs chocolate raisins. These raisins were soft and easy to eat in order to attract the pigs to approach the breeder and have the opportunity to pet the pigs. After 5 days, let the pigs get used to M&M for later testing on the panel. After five days, the handler stopped feeding M&M and petted the pig as much as possible during the habituation period. The habit of testing room and testing equipment lasts for 1 week, twice a day for 30 minutes each time. Then, for a 3-week pre-training phase, the pigs were 7 weeks old. Pigs are trained to lift the ball in search of rewards. Before training, all holes are always rewarded (M&M). During the first 3 days, the pigs used to stay in the five-pig test device twice, each lasting 30 minutes. On the first training day, all the gates of the board were opened. In the next two days of training, only two doors were open (1 and 3; 2 and 4). Then the pigs were trained in pairs for 5 days, twice a day, for a total of 15 minutes. In the first two days, two doors were opened during training, after that, only one of the four doors was opened. Finally, the pigs were trained individually for 1 week, twice a day, until all rewards were consumed or a maximum of 10 minutes. The pigs started formal testing on the board at 11 weeks. The test is divided into two phases: the acquisition phase and the reversal phase. Each pig is assigned to its own reward hole device. Each configuration consists of four bonus holes out of 16 holes. In every rewarded hole, the pig can find an M&M. 20 pigs, using four different configurations. Each pig is tested once in the morning and in the afternoon during the board task. The order in which the pigs enter the experimental field is randomly changed in each trial. The entrance was randomly selected for each pig. During the acquisition phase, the pigs underwent 40 trials in 4 weeks. During the reversal phase, each pig undergoes 20 trials in 2 weeks. During the test (acquisition and reversal), two observers recorded the order of the access holes, the number of reward and non-reward hole visits, the number of reward and unrewarded holes, the number of consumed M&M, and the The incubation period and total test duration of the cavity of a visit. At the beginning of the experiment, the pig entered the test stage. At the end of the experiment, the pig had visited all four bonus holes. When 5 minutes passed, no matter which event occurred first. When the pig uses its nose to arch the ball, the opening between the ball and the bowl can be seen. The device washes feces and urine with water after the pig is tested.

　　Saliva acquisition and basic cortisol analysis: When the pig is about 119 days old, saliva is collected once. In order to explain the circadian variability, saliva was collected at the peak of the cortisol circadian rhythm of pig saliva at 10:00. Use a cotton swab to get saliva. In the laboratory, the saliva samples were centrifuged at 400×g for 10 minutes and stored at -20°C until analysis. A radioimmunoassay kit was used to determine pig saliva cortisol. To avoid batch-to-batch variation, all samples are tested in duplicate on the same day.

　　Result: Spatial memory: Before the start of the formal training, the number of participating different holes was scored 6 days before the training, and all holes were decoyed. During these 6 days, the number of different holes in the two groups was similar. During the acquisition phase, pigs found all four rewards in approximately 95% of the 40 trials. During the reversal phase, pigs found all four rewards in approximately 89% of the 20 trials. Most incomplete trials, i.e. trials where the pig did not find all the rewards, occur in the early stages of acquisition and reversal, respectively.

　　Reference memory: In the acquisition phase, pigs in enriched environments have better memories than pigs in barren environments, but not found in the reversal phase. The reference memory performance of all pigs similarly improved during acquisition and reversal. In the process of acquiring the reversal, the enriched pigs have a better reference memory on average. Working memory (MW): Environmental enrichment has no effect on the average WM performance in the acquisition phase, and has a tendency to improve the WM performance in the reversal phase. The WM performance of both groups improved similarly during acquisition and reversal.

　　Incubation period and duration: First hole latency (LFV): In the acquisition phase and the reversal phase, the environment does not affect the LFV, and the two groups increase in the acquisition phase. Instead, it remains stable during the reversal process. Interview Interval (IVI): During the acquisition phase, the IVI of the poorly raised pigs is longer than the IVI of the environmentally enriched pigs. IVI follows an inverted U shape on the test block during acquisition. Test duration (TD): The average TD-poor pigs in the acquisition phase and the reversal phase are longer than the rich pigs. Both groups similarly reduced the time required to find the four bait holes during acquisition and reversal.

　　Growth curve: The average starting weight of the two groups is similar. The growth curve of enriched pigs wants to have a slightly steeper growth curve than that of barren pigs. Saliva-based cortisol: The average cortisol level of environmentally enriched pigs is lower than that of poor pigs.

　　Conclusion: The results show that pigs raised in a rich environment after weaning show better cognitive ability in the spatial full board task than pigs raised in a barren environment. Both groups improved the performance of RM, WM and GWM in the acquisition and reversal phases. In the acquisition phase, the enriched pigs showed better reference memory performance, while in the reversal phase, they showed slightly better general working memory performance. During the acquisition and reversal phases, environmentally enriched pigs visit the cave faster and require less time to complete the test than barren pigs. The board task is an effective measurement tool for pig spatial discrimination learning. However, it is not clear to what extent the holographic plate test procedure itself can provide enrichment, which may (partially) offset the effects of pigs living in barren environments and may lead to underestimation of the effects of barren environments. Therefore, it may be difficult to test the effects of different environments on the cognitive ability of pigs by using complex test procedures with a longer period of time and appetite motivation.