Rearing without early access to perches impairs the spatial skills of laying hens

The effect of rearing with and without perches on the spatial ability of do mestic hens (Gallus gallus domesticus) was investigated. No access or late access to perches during rearing has been shown to increase the later preva lence of floor eggs and cloacal cannibalism in loose-housed laying hens. Th is may be explained by either the birds reared without perches have difficu lty using perches due to low muscle strength, lack of motor skills, and ina bility to keep balance, or they have impaired spatial skills necessary for moving around in three-dimensional space. These alternative explanations ar e not mutually exclusive. Thirty, day-old chicks were randomly allocated into two equal groups and re ared in litter pens, one with access to perches (P +) and one without (P -) . At 8 weeks of age, all birds were given access to perches, and by 15 week s, all birds were using perches for roosting at night. At 16 weeks, 10 bird s from each group were tested in pens where food was presented on a wire me sh tier 40 cm above the ground (T40). Three consecutive tests, with increas ing difficulty for the bird to reach the food, were then performed. Firstly , the food was presented at 80 cm above the ground but with the tier at 40 cm still present; secondly, food was presented on the tier at 80 cm; and th en, finally, with the food on a 160 cm high tier with the tier at 80 cm sti ll present. All birds were food deprived for 15 h before each test and the time from the bird entering the pen until reaching the food was recorded. T here was no difference in the time to reach the food between P + and P- bir ds in the T40 test. But as the difficulty of the task increased, the differ ence between the P + and P - birds became significant, with the P - birds t aking a longer time to reach the food or not reaching it at all. Since ther e was no difference between P + and P - in the T40 test, it seems reasonabl e to suppose that the later differences did not depend on differences in ph ysical ability. Therefore, the results may imply that rearing without early access to perches, in some ways, impairs the spatial cognitive skills of t he domestic hen. (C) 2000 Elsevier Science B.V. All rights reserved.