WITHDRAWN: The effect of different cage densities on keel bone damage in brown and white laying hens

Abstract

Fractures and deviations of the keel bone are an important welfare problem for laying hens. In this study, keel bone damage (KBD) was investigated by the X-ray method in brown and white laying hens, which were housed at three different cage densities during the laying period. Two different breeds of laying hens, namely, the Isa Tinted (IT) and Hy-Line Brown (HB), were used in the study. The chickens were assigned to three experimental groups, which were housed at a low (5 hens/cage (LCD)), medium (7 hens/cage (MCD)) and high cage density (10 hens/cage (HCD)) during the laying period. In total 396 chickens, comprising 198 HB and 198 IT layers were housed in these cages. Radiographic examination and blood sampling were performed on one chicken from each cage at 35, 51 and 60 weeks, amounting to a total of 54 brown and white laying hens in each period and a total of 162 hybrids for all three periods. X-ray images taken at the end of the study period were scored (0:no deviation, 1:deviation; 0:no fracture, 1:fracture). According to the results obtained, among the hormones involved in calcium metabolism (OC, CT, PTH), only PTH was found to be significantly affected by age (P<0.05) and breed (IT>HB) (P<0.001) The scoring data showed that while the effect of age on fracture and deviation was insignificant; cage density insignificantly affected fracture but significantly affected deviation (P=0.009) (higher rate at LCD). The results of this study demonstrated that conventional cage systems pose a risk for KBD.