Cognition in the chicken (Gallus Gallus Domesticus) : a study of different feather pecking solutions and its effect on learning, memory and emotional reactivity in animals of the White Leghorn and Silver Nick laying hen strain
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The aim of this study is to investigate the influences of two of the main methods for reducing feather pecking in the poultry sector on cognition and behavioral aspects Chickens have highly developed sense of sight and hearing, sense of taste, smell and touch are less represented. However touch is well represented in the beak. Chickens are a highly social species with varied communications patterns. One of the most important behavioral patterns is feeding, this can take op to 90% of the time in the wild. Feather pecking is one of the most severe welfare implications in the poultry sector. Two of the main methods of fighting this problem are genetic selection and beak trimming. The influence of the methods on cognition is important in understanding how these methods relate to the feather pecking problem. Furthermore understanding the performance of cognition and behavioral aspects in chickens are of great importance to establish what chickens need from a (production) environment. Genetic selection is one of the methods used to control feather pecking. However, the way it influences the feather pecking problem is not yet fully known. This was researched by comparing the results of a fourth generation low mortality line with a control line of the white leghorn laying hen strain. The study revealed that chickens have a highly developed working memory and a well developed reference memory. The chickens showed good learning abilities in a spatial hole-board task. No differences were found in performance between the two genetic lines of hens, indicating no effect of this specific selection line on cognition. Beak trimming is a method which has been used for a long time, this method however has its implications on the integrity and welfare. Depending on the method used and the time of trimming, this method can have long lasting repercussions in the form of sensory aphasia, long lasting pain sensation and loss of function in regards to the beak. The effect of beak trimming on behavior was researched by comparing the results with a control line of Silver Nicks of the laying hen strain. If pain sensation as a result of the beak trimming is present this may have influence on sociability, fearfulness or cognition. Sociability tested in a T-maze apparatus revealed no significant differences. This however did not reveal the whole extend of the sociability between the two groups because not all the chicks fully participated in the apparatus. Fearfulness in the two groups was investigated with an open field test; this did not reveal any significant differences. The influence of beak trimming on food manipulation and preference was tested by letting the chickens choose between live and dead bait. The test showed no significant differences between the two groups. However the beak trimmed birds did marginally spent more time eating and pecking at live bait suggesting that they had more difficulty manipulating live bait. Fearfulness and recognition was tested by offering a reward by a familiar and unfamiliar researcher. The test showed no group differences but did show that both groups learned the connection between the researcher and the reward. Both groups approached faster in the second session regardless of the fact that this was with an unfamiliar researcher. This study revealed that genetic selection does not seem to have influence on cognitional aspects as memory and spatial orientation. Other studies suggested that selection does influence sociability, fearfulness and stress response. Beak trimming also did not seem to have influences on sociability and fearfulness but did show slight difference in food manipulation. The chickens in this study do not seem to experience major pain sensation but it is possible they experience sensory aphasia. The influences of genetic selection and beak trimming on cognition and other behavioral aspects need to be further investigated. The results were analyzed with repeated measures ANOVAs and the T-test procedure.