Genetic variation for egg production, egg quality and bone strength in selected and traditional breeds of laying fowl.

1. A multi-breed experiment was conducted with 25 commercial and traditional lines of laying fowl to determine the extent of between-breed genetic variation for adult body weight, sexual maturity, rate of lay, egg weight and egg composition to 55 weeks of age. The genetic variability for bone strength and eggshell strength was determined at 55 weeks of age and a comparison of commercially selected and traditional breeds was performed. 2. The proportion of the total variation that was associated with breed or line of origin was high (> 0.8) for body weight, sexual maturity and shell colour; moderately high (0.4 to 0.7) for rate of lay, early and late egg weight, weights of egg yolk, albumen and shell at 55 weeks; and low (< 0.4) for egg weight at 42 to 45 weeks, albumen quality and the number of egg inclusions. 3. There were no detectable differences between breed within category (traditional and commercial lines) for rate of lay, and estimates of breed variation for egg weight and egg components were substantially decreased within category compared with the overall analysis. 4. Commercial lines displayed earlier sexual maturity, greater rates and persistency of lay, and higher egg weights at earlier (32 to 35 weeks) and later (52 to 55 weeks) ages. At 55 weeks, the larger eggs from commercial birds contained more albumen of higher quality and paler yolks of similar weight to those from traditional breeds. The relative weight of the eggshell was similar in both categories. 5. There was considerable genetic variation between commercial lines for bone density and a moderate proportion of genetic variability for bone strength. Commercial lines had very weak bones compared with traditional lines but there was relatively little genetic variation for eggshell strength. The results suggest that eggshell quality is maintained in genetically selected lines at the expense of bone strength and bone radiographic density.

Age-related changes in fear, sociality and pecking behaviours in two strains of laying hen.

1. Two lines of commercial hybrid layers (Tetra and ISA Brown) were reared from hatch to 30 weeks of age in groups of 8. The objectives of the experiment were to evaluate the significance of the different selection practices involved in the development of the lines and to assess the potential association between selected behavioural states and the potential for feather damage and cannibalism. 2. Behavioural tests related to fear (tonic immobility, novel object, open field), sociality (runway, proximity in the home pen) and pecking (feather bunch and focal observations of inter-bird and environmental pecking) were conducted at 0 to 2, 5 to 7, 12 to 14, 19 to 21 and 29 to 31 weeks of age. Scan sampling of general behaviour was also conducted at these ages. 3. Underlying sociality was greater in Tetras than in ISA Brown hens. 4. There were no apparent overall strain differences in fearfulness although ISA Brown hens showed significantly longer tonic immobility fear reactions than Tetras at 31 weeks of age. 5. ISA Brown hens gave and received more gentle pecks than Tetra hens whereas preening was commoner among Tetras. There were no strain differences in the number of pecks at litter or food. 6. As birds aged they showed less avoidance of novel objects and Tetras, though not ISA Browns, showed progressively shorter tonic immobility responses. Birds of both strains spent less time resting, more foraging (pecking and scratching) and pecked more at the feather bunch at older ages. 7. Measures taken in the TI, open field, runway (social affiliation) and feather bunch tests were stable over time whereas focal observations of pecking at hens and the environment were not. 8. Factor Analysis showed that 3 factors defined by the novel object test, environmental pecking and pecking ata feather bunch explained most of the variation in the correlation matrix between summary measures for the 8 behavioural traits.

Spatial distribution and behaviour of laying hens housed in an alternative system.

The spatial distribution and behaviour of perchery housed laying hens were compared at a constant stocking density (18.5 birds/m(2)) in eight pens with colonies of five different sizes (323 birds (N=1), 374 birds (N=2), 431 birds (N=2), 572 birds (N=1) and 912 birds (N=2)). The birds were placed in the perchery when they were 12 weeks old. Observations began when they were 26 weeks old and continued at 8 week intervals until 61 weeks of age. Colony size did not appear to affect the spatial distribution of birds, but more standing behaviour and less feeding behaviour were observed in the smallest and largest colony sizes. Older birds spent more time on the floor areas and less time on perches. Young birds (26-28 weeks) spent more time feeding, foraging, drinking and preening, and less time standing idle than older birds. In the afternoons, there were fewer birds on the perches and more on the floor levels, corresponding with less time spent resting and more time spent performing active behaviours. Birds did not distribute themselves evenly throughout their pens: within specific areas of pens densities varied between 9 and 41 birds/m(2). This variation, which reflects the flux of birds from one part of the pen to another, was greatest for the larger colony sizes, and may have adverse implications for welfare in terms of crowding and hysteria.