The global move towards cage-free egg production seems to be unstoppable. Far from being restricted to Europe and North America, the commitment of many large egg producers, retailers, food service companies and hotel groups to ban cage eggs from their supply chains is making cage-free eggs a global and ever-increasing reality.
The agri-food industry is under growing scrutiny for its contribution to global warming. Feed contributes to about 80% of poultry’s carbon footprint. The lower feed conversion efficiency associated with cage-free production comes with an environmental burden. When expressed as kilogrammes of CO2-equivalent per kg of eggs produced, aviary and free-range farming increase emissions by 12-13% compared to furnished cages, while organic egg production yields 37% more emissions than furnished cages. Differences in feed utilisation account for about 68% and 43% of these disparities, respectively. Looking at these figures, there seems to be potential to improve the sustainability of cage-free egg production by optimising efficiency. Some options that may help producers achieve this goal are outlined below.
Cage-free systems are generally less efficient than egg production in cages. A renowned breeding company recently published standards for cage, barn/aviary and free-range egg production. According to those standards, the average daily feed intake is moderately higher in cage-free flocks (+7% and +8%, respectively for barn/aviary and free-range, compared to cages). Cage-free flocks also have much higher cumulative bird mortality than caged flocks (+21% and +43%, respectively for barn/aviary and free-range).
For details of the causes which explain the differences in bird mortality rates between housing systems, please see the article ’Cage-free egg production and welfare implications’, previously published in this series.
When the overall impact of the differences in performance is calculated for a production cycle up to 100 weeks of age, the higher cumulative feed intake in barn/aviary and free-range production settings compared to cages (+4.8 kg and +5.3 kg), with an average feed price of € 350 per tonne, amounts to extra feed costs of € 1.68 and € 1.86 per hen housed, respectively, for barn/aviary and free-range operations. For the lower cumulative egg mass (-0.3 kg and -0.7 kg, respectively), using an average egg price of € 1.20 per kg, the negative impact corresponds to a lower egg income of € 0.36 and € 0.84, respectively. Taken together, the increase in feed intake and reduction in egg output, compared to production in cages, will cost at least € 2.04 per hen housed for an aviary/barn egg producer and at least € 2.70 per hen housed for a free-range egg producer.
In addition to the greater intake, other factors contribute to the decreased efficiency of cage-free systems when it comes to converting feed into eggs. When housed in cage-free premises, chickens have contact with soil, litter and manure; this exposes them to higher loads of enteric bacteria, coccidia and other parasites than they would be exposed to in cages.
A recent study has reported diminished intestinal health in birds in cage-free production systems compared to caged birds, with the former tending to have a lower villus height to crypt depth ratio in several segments of the intestine. This can lead to lower intestinal absorption of nutrients and indicates a greater proliferation of new cells for the intestinal lining, which is energetically demanding (and, thus, unfavourable for feed efficiency). The hens used in the study were reported as healthy, which highlights the widespread impact of floor contact on gut health and feed efficiency, even in healthy, cage-free flocks.
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Feather condition and feed efficiency
The effects of cage-free systems on chickens’ feather condition have also been discussed previously in this series of articles. As a brief reminder, feather pecking, which is a major cause of feather loss, can spread more easily and become more serious in cage-free compared to caged flocks, given the larger group size. As a further reminder, the ideal temperature interval for poultry falls within the range of 20-27°C. Lower temperatures are associated with an increase in feed intake, which chickens will use as ‘extra fuel’ to generate more heat to maintain their body temperature.
The degree to which feed intake increases depends on the interaction of two factors: the ambient temperature and the extent of feather damage or loss. Peguri and Coon (1993) reported that feed intake increased by 20 grammes at a temperature of 12.8°C when 50% of the feathers were lost; even at a temperature within the thermoneutral zone (23.9°C), such a level of feather loss increased feed intake by 7 g.
These figures are comparable to those published by van Krimpen and others (2014): At 11°C and 21°C, feed intake increased by 18 g and 4 g, respectively, in hens that have lost 50% of their feathers, compared to fully feathered chickens. Across this temperature interval, the FCR worsened, on average, by 10 points in the birds that had lost 50% of their feathers (2.15 vs. 2.05 in the fully feathered group).
These figures provide a clear demonstration that feather damage is not only a bird welfare problem but also an important economic issue for egg producers. While not all birds within a commercial flock will show the same scale of feather loss at the same time, there will always be a percentage of hens with a considerable degree of feather damage or loss, especially in older flocks.