Effects of different claw-shortening devices on claw condition, fear, stress, and feather coverage of layer breeders

Natural mating colony cage systems for parent-stock layer breeders have been widely adopted by many commercial farms in China. However, the environment is still relatively barren, so enrichment devices such as claw abrasives can be provided. Hens living in wire cages lack the opportunity to abrade their claws, resulting in uncontrolled claw growth. The objective of this study was to investigate the effects of claw abrasive devices (CADs). Three different CADs were investigated: abrasive strips (T1), metal plates with holes (T2) and rubber mats with grooves (T3); cages without CADs acted as controls (T4). Claw length and sharpness, foot health, feather coverage, fear and physiological stress and mortality of the layer breeders were evaluated. Twelve replicates were used for each treatment, a total of 48 identical cages. Results showed that CADs had significant effects on claw length and sharpness of both hens and roosters. Birds in the T1 group had the shortest claw length and bluntest claw sharpness at 22, 32, 42, and 52 wk of age (P < 0.05). T1, T2, and T3 had higher scores for claw condition and significantly better overall plumage condition on the back and rump than T4 (P < 0.05). Hens in the T4 group were more susceptible to the tonic immobility, novel object, and avoidance distance tests. No significant differences were found between groups in concentration of triiodothyronine, thyroxine or 5-HT, except a significantly higher concentration of corticosterone in T4 compared to T1, T2, and T3 (P < 0.05). Overall mortality and mortality from cannibalism were both significantly higher in T4 than in T1, T2, and T3 (P < 0.05). In conclusion, hens with access to CADs during the laying period had shorter and blunter claws, less damaged plumage, a lower plasma corticosterone secretion and mortality rate and were less fearful.