Mortality in Laying Hens Caused by Differences in Cage Design

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Abstract
An introductory experiment with 3 802 Single Comb White Leghorn (SCWL) layers kept in six common different designs of battery cages within the same house was carried out in 1974/75. Each system housed between 476 and 810 hens. All birds were of the same breed and age and received the same feed. The study showed a surprisingly large number of accidents among the hens due to improper and complex cage design in several models. Frequencies of trapped birds varied between the six models from 0.6 to 3.5%, being directly mortal to 90%. Corresponding proportions of the total mortality, including also diseased birds, were 9% and 61% respectively, with an average of 28%. Most accidents happened in the cage front with the neck/head and toe/claw region as well as toes/claws being caught in gaps between cage partitions and the cage floor. In six subsequent trials of the same kind, efforts were made to reduce the incidents by having cage manufacturers alter their designs. Also completely new designs were gradually installed. In this paper 191 incidents in 7 trials from 1974 to 1984 are described, illustrated and classified according to the age of the birds. Steps taken to avoid this excessive mortality are also described. Each trial following the first introductory study comprised about 4000 SCWLs studied from 18 to 82 weeks of age. Altogether the experiments included 26364 birds and more than 40 designs of battery cages originating from 12 different manufacturers. Accidents as a percentage of total mortality averaged 6% in the latest experiment (1983/84). It is concluded that although it was possible to clearly reduce the excessive mortality in the cage designs studied here, there still appears to be a need for poultry farmers and battery cage manufacturers to consider the problem. This is shown to apply both for the welfare of the hen and the economy of the egg producer.

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