Laying hens go undercover to improve production.

DURING 2007, all laying hen producers within the McDonald’s Restaurants UK supply base (McDonald’s Restaurants UK source eggs from free-range UK producers) were required to plant, if not present already, 5 per cent of the total range area in trees. Noble Foods supply free-range eggs into a variety of food retailers not all of which require tree cover on the range. In this study, the authors investigated whether there was a difference between two important production traits: (1) packing station egg seconds and (2) mortality, in matched free-range laying flocks with and without tree cover on the range. In commercial free-range laying systems, the provision of an outdoor range leads to larger space allowances, a higher number and diversity of stimuli, and opportunity to move between environments with different substrate, climatic and light conditions. There is a well-established link between tree cover, range use and injurious feather pecking (an abnormal behaviour that consists of pulling, plucking and damaging feathers of conspecifics (Savory 1995)) in commercial laying flocks; the higher the percentage of flock using the outdoor range, the lower the prevalence of injurious feather pecking (Green and others 2000, Bestman and Wagenaar 2003, Nicol and others 2003, Horton 2006, Lambton and others 2010, Bright and others 2011). If providing tree cover on the range improves bird welfare (as indicated by reduced injurious feather pecking), it might also be expected that tree cover improves production; in livestock production systems, welfare and production traits are invariably linked (Gregory and Grandin 2007). Demonstration of an economic benefit of tree-cover provision would be an added incentive for free-range egg producers to invest in tree planting. Two important production traits for egg producers are egg seconds and mortality. Egg seconds due to poor shell quality are a significant cost to the egg industry (in the UK, a seconds egg is worth about 30 per cent that of a Grade A egg; A. Joret, D. Brass, personal communication). Shell quality is influenced by a number of factors, including nutrition, stress, health status of the hen as well as environmental factors such as temperature, day length and light type (Roberts 2004). The average mortality for free-range laying hen flocks is ~12 per cent (A. Bright, unpublished data). Mortality obviously represents a significant economic cost to producers since birds that die during lay have already consumed significant feed (and other) resource, and fewer birds per house produce fewer eggs. Anecdotal evidence suggests that free-range laying flocks provided with tree cover produce less egg seconds and have lower mortality than those without tree cover (A. Joret, D. Brass, personal communication) although to the authors’ knowledge, there are no scientific studies comparing such production traits and tree cover in free-range laying hens. In a commercial operation, egg seconds are collected on farm and at the packing station. Farm seconds are eggs with visual faults (eg, calcified, discoloured, dirty, misshapen, obvious cracks) detected at egg collection and are due to stress/disease and location of lay (Roberts 2004, A. Joret, D. Brass, personal communication). The recording of farm seconds is variable across producers because of off-farm sales. At the packing station, all eggs are candled to detect cracks and other defects not visible to the naked eye and are also due to stress/diseaserelated factors (Roberts 2004). Packing house seconds are always recorded because they determine payments made to the producer. Packing station egg seconds and mortality data were collected from 33 free-range flocks with tree cover on the range and 33 freerange flocks without tree cover on the range. Flocks were matched for strain, flock size (tree-cover flock size: mean=9457, SE=660, range=4300 to 16,000; without tree-cover flock size: mean=9334, SE=658, range=4550 to 16,000) and week of placement at the laying hen farm. All flocks with tree cover had >20 per cent canopy cover (Bright and others (2011)). The packing station egg seconds were averaged for (1) the entire production life of the flock and (2) the ≥45 week to the end of lay period (a time when egg seconds are a particular problem, D. Brass, A. Joret, personal communication); flock mortality was calculated as total flock mortality over the lay production period and was determined from daily record sheets of culls and birds found dead in the house or range. The causes of flock mortality were not specified further than ‘disease challenges and other stress-related factors’. Flock egg seconds and mortality data were log 10 transformed to meet the assumptions of normality and homogeneity of variance. A paired sample t test was carried out using SPSS 16 for Windows (SPSS 2007). In flocks with tree cover, there were less total egg seconds (t32=1.89, P=0.07; Fig 1a) and significantly less ≥45 week egg seconds (t32=2.21, P=0.04; Fig 1b) than flocks without tree cover. There was also lower mortality in flocks with tree cover (Fig 2) although this was not statistically significant at P<0.05 (t32=1.67, P=0.1). Short Communications