Imagine two people who share a house and eat the same food but when it comes to exercise, one is a couch potato and the other a runner.
That’s the analogy University of New England researcher Isabelle Ruhnke uses to explain her latest experiment comparing egg production rates of free-range hens that like to roam, compared with those that don’t venture out.
And her findings go against what the industry expected.
“We had the initial hypothesis that the birds that go and range are not doing as well as the ones that stay in the shed around the nice feed, close to the nest box,” Dr Ruhnke said.
“But quite the opposite was true.”
The study saw 16,000 hens fitted with microchip bands on their legs and antennas around the property tracked their movements from 16 to 72 weeks of age.
“These ‘rangers’… were outside within that first time period of 22 weeks of age, and when we looked at the egg production they laid about 15 per cent more eggs in the nest box than these birds that stayed in the shed,” Dr Ruhnke said.
“It wasn’t until they were 52 weeks of age, that the ‘stayers’ laid more eggs than those birds that would go out and range, which is really significant.
Are the stayers ‘chicken’?
Non-for-profit organisation Australian Eggs co-funded the research and managing director Rowan McMonnies said it was the first time sub-populations in free-range hens had been examined.
“It was difficult to know what to expect,” Mr McMonnies said.
“There has been an assumption within the industry that production was closely linked to food intake but the research shows the nature of the hen could be a strong factor.