Increasing Energy and Amino Acid Levels in Layer Diets Improved Laying Performance but not Egg Quality in Ranging Free-Range Hens

It has been proposed that the metabolic energy requirements of free-ranging hens are up to 15% higher compared to caged hens due to the increased metabolic activity required for locomotion and thermoregulation (GfE 1999; Tiller 2001; Aerni et al. 2005). The aim of the study was to investigate the impact of various feed strategies on laying performance and egg quality of free-range laying hens. A total of 9,375 hens, placed amongst 5 flocks of 40,000 hens each were selected according to their range usage (hens accessed the range at least 70% of available days at 18-22 weeks of age). For each of the flocks, these rangers (outdoor preferring hens) were randomly separated into 3 treatment groups of 625 hens per replicate/flock housed in 3 identical partitions amongst their flock mates. Each of the three treatment groups was fed either a standard commercial diet (T1), allowed access to an outdoor feeder filled with the standard commercial diet (T2), or were fed with a diet containing + 10% Metabolisable Energy (ME) and +10% increased amino acids compared to the standard commercial diet (T3). All in-shed diets (T1, T2, T3) were delivered via a feeding chain, the additional outdoor feeder (T2) was available ad libitum during pop hole opening times (9am-8pm). A mixed restricted estimate of maximum likelihood (REML) model with the flock as a random factor, and treatment group, hen age and their interactions as fixed effects was used to analyse laying performance, egg quality and body weight. Feeding T3 resulted in significantly higher laying performance at 52, 62 and 72 weeks of age compared to hens that were fed T1 and T2. Albumen height decreased with the age of the hens (P < 0.001) but adding an extra 10 % ME and inclusion of the outdoor feeder had no effect on the albumen height (P = 0.56). Age of the hen, treatment and their interaction had an effect on the yolk colour (P < 0.001) where the addition of extra of 10% ME had effect of yolk colour at 42 weeks of age only. The rangers fed with extra 10 % ME (T3) had a darker yolk colour compared to all other treatment groups. There was no significant difference in body weight between all treatments at 16, 22, and 74 weeks of age (P> 0.05). In conclusion, increasing energy and protein levels of the diet increased laying performance significantly at end of lay with minor impact on egg quality. This may be relevant when considering extending flock use to 100 weeks of age and beyond.

Table 1 - The difference in egg laying performance between hens fed a conventional diet, hens using an outdoor feeder, and hens with a diet with extra 10% ME and 10% CP.

ACKNOWLEDGEMENTS: Australian Eggs and Poultry CRC funded this project 1UN151.