Feather pecking and cannibalism in free-range laying hens as affected by genotype, dietary level of methionine + cystine, light intensity during rearing and age at first access to the range area

Abstract

An experimental small-scale free-range system was used in the two experiments reported here and consisted of 24 independent units. Experiment 1 was designed to test genotype and level of dietary methionine+cystine. Four genotypes were used: ISA brown (ISA), new hampshire (NH), white leghorn (WL) and a cross between NH and WL (C). In the laying period the content of the essential amino acids methionine+cystine in the food was either low (4.0 g/kg) or high (8.0 g/kg). Experiment 2 was designed to test three genotypes, two levels of light intensity (3 or 10 lx) and early (4 weeks old) versus late (16 weeks old) access to the range area. The genotypes used were ISA, Lohmann selected leghorn (LSL) and Danish landrace (DL). The level of feather pecking was in general low in both experiments. In experiment 1, at 14 weeks, NH-birds gave significantly fewer bouts of feather pecking than ISA and C, while C gave more pecks than NH and WL. In experiment 2, at 11 weeks, ISA gave significantly fewer bouts as well as feather pecks compared to DL and LSL. In experiment 1, the plumage of 98% of ISA-hens, 70% of C-hens, and 31% of NH-hens was damaged at 35 weeks, while none of WL-hens had any damage. Damage to feathers at the back, which mostly results from feather pecking, corresponded well with these figures of general damage. In experiment 2 this was not so. The plumage of 54% of DL, 10% of ISA and 70% of LSL was damaged, but 54, 1 and 1%, respectively, had suffered damage to the back feathers, indicating feather pecking in DL and not in the other genotypes. Age at access to the range and light intensity during rearing did not affect the plumage condition of ISA and LSL at 35 weeks. In experiment 1, mortality from cannibalism was higher in ISA compared to the other genotypes (17.5, 2.4, 0 and 1.1% in ISA, NH, WL and C, respectively). Mortality from impaction (mainly grass) was higher in NH than in ISA and WL. A high and significant, positive correlation (0.60–0.80) was found between feather or skin damage and mortality from cannibalism. Plumage condition recorded at the post mortem examination was worse for hens diagnosed dead from cannibalistic pecking compared to other diagnoses (16.4 versus 19.7 points, P<0.001).