Substituting soya meal with home-grown protein may not have as much effect on reducing the carbon footprint of poultry production as many believe, according to a project carried out at Newcastle University.

“Greenhouse gas emissions from land use change related to the cultivation of soya are one of the main components of the overall global warming potential (GWP) of poultry products,” said the university’s Ilkka Leinonen. “So, alternative protein sources in poultry feed would be expected to reduce the environmental impact of the industry.”

But this was not borne out by Life Cycle Assessment (LCA) modelling carried out by the university. This took account of all production processes, from the initial deforestation to grow the soya right through to the final production of the finished broiler or egg, plus distribution.

The work compared standard soya-based diets with alternatives based on beans, peas, sunflower or rapeseed.

While it was found that the use of European protein sources, such as beans and peas, did have the potential to reduce total greenhouse gas emissions, it was only by small amounts.

“These reductions were relatively small because there is a limited amount of soya that can be removed from the diet, while other ingredients with a high global warming potential, including vegetable oil blends and pure amino acids, had to be added to the alternative diets,” explained Dr Leinonen.

The diet with sunflowers actually increased the global warming potential, partly because it required a high level of vegetable oil blend, including palm oil. The study was carried out as desk research, using typical production and dietary formulation data provided by the industry.

All diets were adjusted to maintain energy and nutrient levels, and the assumption was made that the alternative ingredients had no inherent effects on bird performance.

“Furthermore, quantification of other environmental data, including eutrophication and acidification potentials, is needed to make a holistic judgement of the impact of these ingredients.”