Byproducts from nut production could successfully replace conventional livestock feeds and provide additional health benefits for animals, according to University of Catania-led research.
Agricultural scientists carried out a review of evidence to date on feeding livestock the hulls, skins and oil cake of almond, pistachio, hazelnut and walnut.
They concluded that almond hulls are fibre-rich and can be used as an energy feed for ruminants up to an inclusion rate of 250g/kg, nut oils could partly replace soybean as a protein source for poultry and pigs, while feeding animals hazelnut skin can improve the fatty acid profile of meat and milk, thereby making it healthier for humans to eat.
“The byproducts of temperate-climate nuts can replace conventional feedstuff, provided that the diet is properly formulated. These by-products contain bioactive compounds, such as phenolic compounds, polyunsaturated fatty acids, and vitamins, which could provide benefits for animal health and final products,” they wrote in the journal Animal Feed Science and Technology.
Work to do before nuts are the norm
While making use of the byproducts would improve the sustainability of both the feed and nut production industries through the use of circular economy principles, the review highlighted that the route to widespread use of what is left behind as nuts are readied for consumption is far from straightforward.
In feeding the world’s livestock, one aspect to consider is nuts’ high levels of phenolic compounds, the scientists stressed. These plant chemicals can reduce effective digestion at certain thresholds but can also have positive effects on animal health and product quality. Nut byproduct-based feeds may overall be more suitable for ruminants, which can better digest and metabolise this type of biomass.
The review also revealed that there is great variability in the nutritional content of the same nut byproduct, with factors such as the cultivar grown and environmental conditions having an impact. This would mean that chemical analyses would likely need to be completed for each batch prior to feeding them to animals.
Industry unknowns
There are further issues with being able to predict the quantity of byproducts that would be available for feed, the researchers wrote, given that only those intended for fresh consumption, as opposed to confectionary or oil extraction, would likely be available.
Other byproducts from nuts grown in temperate climates, such as chestnuts and cull peanuts (peanuts not suitable for human consumption) have yet to be explored as possible feedstuffs, they added, meaning that this is an avenue for future research. There is also a need to assess possible health hazards from contamination and calculate the overall sustainability of nut byproducts’ use as feed by carrying out life cycle assessments.
