Keel bone damage (KBD) is a critical issue facing the laying hen industry today as a result of the likely pain leading to compromised welfare and the potential for reduced productivity. Recent reports suggest that damage, while highly variable and likely dependent on a host of factors, extends to all systems (including battery cages, furnished cages, and non-cage systems), genetic lines, and management styles. Despite the extent of the problem, the research community remains uncertain as to the causes and influencing factors of KBD. Although progress has been made investigating these factors, the overall effort is hindered by several issues related to the assessment of KBD, including quality and variation in the methods used between research groups. These issues prevent effective comparison of studies, as well as difficulties in identifying the presence of damage leading to poor accuracy and reliability. The current manuscript seeks to resolve these issues by offering precise definitions for types of KBD, reviewing methods for assessment, and providing recommendations that can improve the accuracy and reliability of those assessments.

The objective of this study was to compare the flock-level prevalence of healed keel bone fractures and to benchmark other indicators of well-being in laying hens housed in conventional cages and single-tier floor housing systems at several points during the production period. Commercial farms in Ontario, Canada, that housed hens in cages (n=9) or floor barns (n=8) were included. Flocks were beak-trimmed brown hens of various strains. Each flock was visited at 20, 35, 50, and 65 wk of age. At each visit, 50 hens were weighed, palpated for healed keel fractures, and feather scored over 4 areas of the body. Data were collected from the farm records on cumulative mortality. Keel fracture prevalence was higher in floor-housed flocks compared to cage-housed flocks (48.3±0.04% vs. 24.8±0.03%; P<0.001). The majority of keel fractures occurred by 50 wk. Cumulative mortality tended to be higher in floor-housed flocks compared to cage-housed flocks (2.13±0.42% vs. 1.29±0.19%; P=0.078). Mean BW was lower (1,827±28.8 g vs. 1,888±26.8 g; P=0.02) yet more uniform (CV of BW 9.43±0.40% vs. 10.10±0.32%; P<0.001) in floor-housed flocks compared to cage-housed flocks. Feather condition was not affected by housing system type (P=0.618), although it declined with age (P<0.001). Individual hen factors assessed using Pearson partial correlations indicated that hens with fractures were heavier at 65 wk in both housing types (P<0.05) and that heavier hens housed on the floor had better feather scores (P<0.001) from 35 wk onward. Floor-housed hens with fractures had lower feather scores at 35 wk (P<0.05) but not at 50 or 65 wk. Housing hens in single-tier floor systems increased the flock-level prevalence of keel fractures and resulted in a lower, yet more uniform, BW compared to hens in conventional cages under commercial conditions in Ontario. Benchmarking welfare indicators from alternative housing systems for laying hens is important to ensure that progress is made in improving their well-being.

No abstract

The objective of this study was to assess the interobserver reliability (agreement) and accuracy of keel palpation for the purpose of detecting old fractures in an end-of-lay flock of commercial laying hens. The low level of invasiveness and the relative speed at which this evaluation can be carried out lends itself well to use in a welfare audit, but only if the results are reliable and accurate from various assessors. The palpation technique first described by Wilkins and others (2004) was used to manually palpate for keel fractures. The technique was modified in that only keel fractures were considered. Eight assessors with varying laying hen experience palpated 100 live ISA Brown hens that had been in lay for 49 weeks. The hens were then euthanased and examined by dissection to establish whether there had been a keel fracture present (yes/no). The accuracy for individual assessors ranged from 87.1 to 96.8 per cent, with a mean of 91.8 per cent among all eight assessors. The interobserver reliability among all eight assessors was moderate (κ=0.44). Accuracy and κ values were 84.8 per cent and 0.41 for the first 50 hens, and 99.5 per cent and 0.47 for the last 50 hens, respectively, indicating that there was increased accuracy and agreement as the assessors became more experienced at palpation. This level of agreement, and the high level of accuracy, would make this technique an acceptable measure of keel fracture prevalence in a welfare audit.

No abstract