Transforming Fruit and Vegetable Wastes into Nutritious Animal Feed

Every year, fruit and vegetable processing industries generate millions of tonnes of waste – peels, seeds, pulp, and pomace – most of which ends up in landfills. This creates serious environmental problems, from greenhouse gas emissions to soil and water contamination. But here’s the thing: these so-called “wastes” are actually packed with protein, fibre, fats, vitamins, and bioactive compounds that make them perfectly suitable as animal feed. Turning processing leftovers into nutritious livestock feed is one of the smartest ways to close the loop in food production – saving money for farmers, reducing pollution, and feeding animals sustainably.

Why fruit and vegetable processing wastes matter for animal nutrition 🔗

According to the Food and Agriculture Organization (FAO), fruit and vegetable processing, packing, distribution, and consumption in major producing countries generate tens of millions of tonnes of organic waste annually. Globally, fruits and vegetables have the highest wastage rates among all food categories – roughly 40-50% of total production is lost or wasted at various stages.

What makes these wastes valuable is their nutrient profile. Research published in Frontiers in Sustainable Food Systems confirms that fruit and vegetable waste (FVW) is a meaningful source of functional compounds – including dietary fibre, polyphenols, minerals such as calcium, phosphorus, potassium, iron, and zinc, and essential vitamins. These nutrients can support bone development, immune function, oxygen transport, and overall metabolic health in livestock. Rather than discarding this material, redirecting it into animal feed contributes directly to sustainable livestock production and reduces the pressure on conventional feed resources like maize and soybean.

Key fruit processing wastes used as animal feed 🔗

Citrus peels and pulp 🔗

Citrus processing – primarily for juice – leaves behind 50-70% of the original fruit weight as waste, including peel, pulp, rag, and seeds. This residue is one of the most widely used fruit by-products in animal feeding worldwide. Dried citrus pulp is considered a high-energy feed with a total digestible nutrient (TDN) content averaging around 74%. It serves as an effective replacement for cereal grains like corn in cattle diets. In fact, up to 40-45% of ground corn in a dairy ration can be replaced with dried citrus pulp without negatively affecting animal performance.

Citrus pulp is especially beneficial for dairy cattle, where the extensive acetic acid production it promotes in the rumen helps maintain milk yield and milk fat content. For beef cattle, dried citrus pulp can be safely included at 20-30% of the dry matter in fattening rations. It is also a good source of calcium, though its phosphorus content is quite low – so rations need to be balanced accordingly. Fresh citrus pulp can be ensiled for year-round feeding, which is particularly useful in tropical regions where the citrus harvest season coincides with the dry season when grass is scarce.

One important precaution: feeding very high levels of citrus pulp (above 60% of concentrate) without adequate forage can lead to rumen parakeratosis, a digestive condition where the rumen wall becomes damaged. Gradual introduction and moderate inclusion levels are key to safe feeding.

Tomato pomace and seeds 🔗

Tomato processing for paste, juice, and ketchup generates a by-product called tomato pomace – a mixture of skins, pulp, and crushed seeds that accounts for 10-40% of processed tomato weight. This pomace is surprisingly nutrient-dense. According to a review published in the journal Animals, tomato pomace contains approximately 33% seeds, 27% peel, and 40% pulp. It is rich in protein (15-22%), fat (8-16%), dietary fibre, and important bioactive compounds like lycopene, beta-carotene, and tocopherols.

For poultry, tomato pomace has shown promise as a partial replacement for expensive protein sources like soybean meal. Studies have found that including up to 12-15% dried tomato pomace in poultry diets can improve immune response, antioxidant capacity, and even egg quality – particularly through increased lycopene deposition in egg yolks. However, the high fibre content of tomato pomace limits its metabolisable energy for birds, so careful formulation is necessary.

In ruminant diets, tomato pomace performs well because the rumen’s microbial ecosystem can efficiently break down its fibre content. Research has shown that dried tomato pomace can completely replace urea-treated straw in heifer diets, improving rumen digestion and feed efficiency. It can also be ensiled or fermented to extend its shelf life and enhance digestibility.

Mango kernels and peels 🔗

Mango processing generates large quantities of peels and seed kernels. Mango seed kernels, once properly processed to remove anti-nutritional factors like tannins, contain approximately 10-15% protein along with significant amounts of healthy fats. This makes them a viable ingredient in poultry and swine diets. Mango peels, on the other hand, are a source of fibre and energy, and can be dried and incorporated into ruminant feed formulations. The FAO’s technical document on fruit and vegetable waste utilisation covers detailed guidelines on the inclusion of mango by-products in livestock rations.

Other valuable fruit wastes 🔗

Several other fruit processing by-products also serve as effective feed ingredients. Apple pomace, the residue from cider and juice production, is rich in soluble sugars and pectin and works well as an energy supplement for ruminants. Grape pomace, left over from wine production, contains polyphenols and dietary fibre that can improve the fatty acid profile and oxidative stability of dairy products. Banana peels and pineapple waste (crowns, cores, and peels) are also nutrient-rich and are commonly used in tropical livestock systems. A review in the journal Agriculture notes that these by-products are rich in cellulose, minerals, vitamins, polyunsaturated fatty acids, and phytochemicals, all of which can have positive effects on animal health and product quality.

Vegetable processing wastes as feed 🔗

Vegetable processing also generates considerable amounts of usable by-products. Cauliflower and cabbage leaves with stems are rich in proteins, soluble sugars, and both macro and micro minerals. Pea pods, carrot pomace, potato peels, and bottle gourd pulp all have nutritional value for ruminants when properly processed. According to research published in Waste Management, substituting 10% of the concentrate mixture with fruit or vegetable waste in sheep diets maintained nutrient utilisation while improving antioxidant status and reducing environmental impact through lower greenhouse gas emissions.

One practical advantage of vegetable wastes is that many of them – such as cabbage leaves and carrot tops – can be fed fresh to animals with minimal processing. However, their high moisture content (often above 80%) means they spoil quickly, so drying or ensiling is recommended for longer-term storage.

Processing techniques: from waste to feed 🔗

Raw fruit and vegetable wastes cannot always be fed directly to animals. Several processing steps are needed to improve their shelf life, safety, digestibility, and nutritional value.

Drying 🔗

Sun drying and mechanical drying are the most common methods. Drying reduces moisture content (often from 80-90% down to about 10-12%), which prevents microbial spoilage and makes the material easier to handle, transport, and mix into compound feeds. Dried citrus pulp, dried tomato pomace, and dried mango kernel meal are all examples of commercially dried waste-to-feed products. The drying process also concentrates nutrients on a dry matter basis, making the final product more energy-dense.

Ensiling 🔗

Ensiling (silage making) involves packing moist waste material under anaerobic conditions, allowing natural lactic acid fermentation to preserve it. This method works particularly well for materials with adequate sugar content, such as citrus pulp and fruit pomaces. Ensiling can maintain or even improve the nutritional quality of the waste while extending its usability for year-round feeding. Mixing high-moisture wastes with drier feedstuffs – like straw, hay, or fibrous crop residues – helps achieve the ideal moisture level of 60-70% for successful fermentation.

Pelletising 🔗

After drying and grinding, wastes can be compressed into pellets, which are convenient for storage, transport, and controlled feeding. Pelletised citrus pulp, for instance, is traded globally as a standard feed ingredient. Pelletising also reduces dustiness and feed wastage during handling.

Fermentation 🔗

Microbial fermentation – using bacteria, yeasts, or fungi – can enhance the protein content and digestibility of fruit and vegetable wastes. Fermentation breaks down complex carbohydrates and anti-nutritional factors, making nutrients more accessible to the animal. Fermented tomato pomace, for example, has been studied as a replacement for soybean meal in dairy cow diets with promising results, maintaining milk production while improving antioxidant capacity.

Matching wastes to the right animals 🔗

Ruminants (cattle, sheep, goats) 🔗

Ruminants are particularly well-suited to consume fruit and vegetable processing wastes because their complex, multi-chambered digestive system can ferment and extract nutrients from high-fibre materials. Citrus pulp, tomato pomace, apple pomace, grape pomace, and various vegetable leftovers can all be incorporated into ruminant diets – often replacing portions of traditional forages or concentrates. As noted in a review in the MDPI journal Agriculture, these by-products can serve as functional feed ingredients that not only nourish the animal but also improve the quality of meat and milk products through their bioactive compound content.

Poultry 🔗

Poultry have simpler digestive systems, so feeding them processing wastes requires more careful formulation. High-protein materials like tomato seed meal and properly processed mango kernel meal can partially replace costly conventional protein sources. However, inclusion rates need to stay moderate – generally below 15% for tomato pomace – to avoid issues with high fibre and anti-nutritional factors. The key is adequate processing (drying, grinding to appropriate particle size, and sometimes enzyme supplementation) to maximise nutrient availability.

Swine 🔗

Pigs can utilise certain fruit and vegetable by-products, though their tolerance for high-fibre ingredients is lower than that of ruminants. Properly processed fruit wastes at moderate inclusion levels (typically under 10%) can contribute useful energy and nutrients without compromising growth performance.

Benefits beyond nutrition 🔗

Converting fruit and vegetable processing wastes into animal feed delivers multiple benefits that go well beyond simply feeding livestock.

Reduced waste disposal costs: Processing plants save significantly on waste management when by-products are diverted to the feed industry rather than sent to landfills or incineration. Lower feed costs for farmers: These by-products are typically available at a fraction of the cost of conventional ingredients like corn and soybean meal, making livestock production more affordable. Environmental gains: Diverting organic waste from landfills reduces methane emissions. Research also suggests that certain by-products – particularly those rich in polyphenols like grape pomace – can actually reduce enteric methane emissions from ruminants, further lowering the carbon footprint of livestock farming. Improved product quality: Bioactive compounds in these wastes, such as lycopene from tomatoes and polyphenols from grapes, can enhance the antioxidant properties, colour, and shelf life of animal products like eggs, meat, and milk.

Challenges to keep in mind 🔗

Despite the clear potential, there are practical challenges. The high moisture content of fresh wastes makes them highly perishable and expensive to transport. Seasonal variability means the type and volume of available waste changes throughout the year, making consistent feed formulation difficult. Some by-products contain anti-nutritional factors – such as tannins in mango kernels, limonin in citrus seeds, or solanine in potato peels – that must be reduced through processing before feeding. Potential pesticide residue contamination also needs monitoring, especially in peels that are directly exposed to agricultural chemicals. Finally, standardising the nutritional composition of these highly variable materials remains an ongoing challenge for the feed industry.

What do you think? With millions of tonnes of fruit and vegetable waste generated every year, could waste-to-feed programmes become a standard part of food processing operations in your region? What other creative ways can you think of to add value to agricultural by-products?

References

1. https://www.fao.org/4/i3273e/i3273e.pdf
2. https://www.frontiersin.org/journals/sustainable-food-systems/articles/10.3389/fsufs.2025.1512577/full
3. https://www.feedipedia.org/node/680
4. https://pmc.ncbi.nlm.nih.gov/articles/PMC9736048/
5. https://www.mdpi.com/2077-0472/13/2/286
6. https://www.sciencedirect.com/science/article/abs/pii/S0956053X21002488
7. https://www.mdpi.com/2077-0472/5/4/1020