FROM THE FRONT LINE
Some free-range chooks lay substantially more eggs than others, and Manisha Kolakshyapati, from The University of New England, is trying to find out why.
Growing up in Nepal, Manisha Kolakshyapati was surrounded by animals. Her father was a professor in agriculture and the family lived on a university campus. “We had access to a whole lot of animals and I enjoyed being around them – I liked it there,” she says.
It therefore wasn’t a huge surprise when Kolakshyapati decided to follow her father’s footsteps, working with animals and exploring how to improve food production. Initially studying veterinarian science in Nepal, she went on to pick up two postgraduate degrees – a Masters in Animal Science, from the Swedish University of Agricultural Sciences, and a Masters of Food Science from the University of Helsinki.
She returned to Nepal to work as a scientific researcher and veterinarian for the government, and now she’s working on a PHD at the University of New England.
The focus of much of Kolakshyapati’s early research was on broilers, but for the past two years she has been targeting egg production, and in particular production in free-range chickens.
The rise of consumer interest in and demand for free-range eggs has led to a substantial increase in production in Australia and elsewhere over the past decade. In 2010 just 25% of Australia’s eggs were free-range, now it’s around 40% of the 100 million eggs sold each week. Of our 19 million egg-laying chickens, about 10 million are housed in cages, with the rest in barn or free-range production.
Free-range flocks often perform poorly compared with hens housed in barns or cages and within free-range chook populations, some chickens are better layers than others. Kolakshyapati set out to find out why and quickly discovered that the reasons are surprising.
“Chickens always form subpopulations,” she says. “In free-range populations, some hens will always go outside if given the opportunity. We call these ones the rangers. Others prefer to stay inside the sheds.
We call these the stayers.”
Different farms have different percentages of stayers and rangers.
For example, in the UK (perhaps where conditions are colder outside) up to 50% of a free-range population may be stayers, but in Australia the average percentage is 10%.
Kolakshyapati initially thought that the rangers would be using more energy to move around further, so would probably not be as productive in terms of laying eggs as they would be using the energy for mobility. “But the ones that were going outside were producing more eggs,” she says. “We were expecting the positive production difference in the stayers, but it’s happening the opposite way.”
The surprising result has led Kolakshyapati and other researchers on a quest to try to determine why – considering factors such as genetic differences or dietary differences (rangers may be ingesting more dirt, or pasture or microbes that could be helpful).
One of the key differences she has found is that the stayers seem to be more fearful birds, and this is likely to be affecting their production. When she took a group of stayers and a group of rangers into a different environment, the stayers showed more fearful behaviours – for example, in their interaction with a new environment.
“If a hen is stressed, she will allocate
energy towards a physiological stress response and, if this is a chronic state of stress, it will have long-term impacts on welfare and productivity,” she says.
“Evaluating the egg albumen corticosterone level, an indicator of physiological stress, we showed that stayers were less resilient to stress and took more time to recover after a stressful event. Stayers likely allocate more of their energy to a physiological stress response, leaving less energy for production, growth and maintenance.”
While the corticosterone results indicated that the stayers were less resilient to stress compared to the rangers and a control group, these results aren’t definitive on their own and are being compared with behavioural studies to develop a better picture in regards to the link between fear and poor egg production.
The differences between the rangers and the stayers might resolve over time. “With time, most of the stayers started going out more,” Kolakshyapati says. “We see that the heavier pullets end up being rangers, and the lighter ones are stayers. So it might be related to weight.”
There’s no doubt Kolakshyapati still has great enthusiasm for her subject, even as her PHD moves into its third year. This is particularly helpful as she looks at the role of gut microbiota and the role it could have on egg laying. “Studies into environmental enrichment could also show an effect,” she says. “The free rangers seem to like a new environment, so maybe that could be a factor. The more we look into it, the more we find to look into.”