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Using alternative sources for animal feeds can provide two valuable functions: 1) reducing the costs of feeds; and 2) reducing food and feed wastes and thus costs associated with treating or disposing of unwanted or wasted food or feed. The incorporation of higher environmental standards in agriculture practices is leading to sustainable and efficient systems. However, the generation of food waste has been a constant challenge in achieving the efficiency needed to reach the sustainable environmental standards in agriculture. Here, it is important to understand what constitutes food waste. There are multiple definitions of food waste as defined by different organizations (Ishangulyyev et al., 2019). The food waste occurs along the entire spectrum of farm to fork. Based on the location of the ‘waste’ event, it can be categorized as – 1) food loss, when the waste emanates from agriculture production and through the supply chain (storage, processing, and distribution) and 2) food waste, when consumable food is discarded intentionally at retail and consumption level (WFPUSA, 2021). An interesting fact about these wastes is that food wastes (losses at retail or during consumption) occur mostly in developed countries and food loss (on the farm or during storage or shipping) primarily occurs in developing countries. A total of over 30% of food is lost as waste from harvest to consumer levels. Globally, 14 percent of food valued at an estimated USD 400 billion is lost from harvest up to, but not including retail (FAO, 2019). An additional 17 percent more is wasted at the retail and consumer levels (UNEP 2021). The amount of Food Waste (FW) in industrialized countries, at approximately 222 million tons, is almost equal to the total net production in Sub-Saharan African counties (230 million tons) (Gustavsson et al., 2011).

By-products are generated from the food loss and wastes and includes fractions that can be utilized as feed ingredients. These can originate from 1) cereal and oilseed processing, 2) fermentation-based processes like brewery, distillery, and ethanol production, 3) fruits and vegetable processing, and 4) livestock processing. Currently, a significant portion of the feeds formulated in North America consists of grains, pulses, and oilseeds and commodities like potatoes. By contrast, approximately 60% of the daily municipal waste is converted to animal feeds in Japan and South Korea, making them the global leaders in converting wastes to animal feed ingredients (Nguyen et al., 2017). Thus, there is a tremendous scope of utilization of by-products as animal feeds.

Challenges of By-product Utilization in Animal Feeds

Skip to Challenges of By-product Utilization in Animal Feeds

Even if there is availability of by-products, their utilization as a feed ingredient to the fullest potential has not been realized due to the challenges listed below:

Nutritional variability – Due to the heterogeneity in the food wastes, it is often difficult to produce feed ingredients with a consistent nutritional profile. This leads to difficulties in making nutritionally balanced feeds on a regular basis.

Feed safety - The by-products diverted for animal feed production should be safe for animal consumption. There is a chance of contamination of this by-product stream due to microbial contamination, presence of mycotoxins, heavy metals, packaging plastics, and other contaminants.

Regulatory compliance – The regulatory standards for inclusion of by-products as feed ingredients is defined by FDA and Association of American Feed Control Officials (AAFCO) in the US. The approved by-products have to meet the regulatory standards, whereas by-products emanating from novel ingredients have to holdup its inclusion until accepted and defined by AAFCO.

Logistics – The efficient collection of by-products is often a challenge because of the diverse and non-consistent production of by-products, generally from urban locations. Often these by-products are easier to be taken to landfills. Further, transporting the collected food wastes/by-products to long distances for further upcycling may not be a viable option due to the associated economics of shipment.

Environmental impact – The fate of by-products/food waste depends on the end use. Of the several strategies to utilize the by-products, those with minimal greenhouse gas production would be favored. For example high moisture by-products, if they have to be transported to longer distances for utilization would produce higher GHGs as compared to diverting it to composting etc. locally.

Economics – The primary reason for inclusion of by-products in feeds is to reduce the cost of the feed. If seasonality affects the availability of by-products then the feed manufacturers have to weigh in the pros and cons of changing the formulations. Additionally, if these by-products need specialized storage then that will need additional investments. Finally, these by-products should be lower in costs nutritionally as compared to the ingredient that it is replacing.


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It is important to keep by-products away from landfills to promote sustainability and reduce environmental pollution. These potential feed ingredients can also reduce the cost of producing animal feeds. Of the several ways of utilizing by-products, use as feed ingredients is a suitable strategy. The ability of livestock to utilize these by-products helps the by-product producers, feed manufacturers, and animal farmers to lower their respective environmental footprint and can be a win-win for all participants. Careful consideration must be given while using these as feed ingredients to meet the nutritional requirements of the livestock in a safe manner. Several challenges may occur in the process of utilization of by-products, especially high moisture products or by-products from novel sources of food. However, proper handling during manufacturing of feed and good knowledge of nutritional requirements of the animal can largely mitigate these challenges.


Skip to References

Ishangulyyev, R., Kim, S., & Lee, S.H. (2019). Understanding food loss and waste – Why are we wasting and losing food? Foods, 8(8): 297.

FAO (2019). Moving forward on food loss and waste reduction. The state of food and agriculture 2019. Rome (Italy).

Gustavsson, J., Cederberg, C., Sonesson, U., van Otterdijk, R., & Meybeck, A. (2011). Global Food Losses and Food Waste. FAO; Rome (Italy).

Nguyen,D.D., Chang, S.W., Cha, J.H., Jeong, S.Y., Yoon, Y.S., Lee, S.J., Tran, M.C., & Ngo, H.H. (2017). Dry semi-continuous anaerobic digestion of food waste in the mesophilic and thermophilic modes: new aspects of sustainable management and energy recovery in South Korea. Energy Conversion and Management, 135: 445-452.

UNEP (2021). Food Waste Index Report 2021. Nairobi, Kenya.

WFPUSA (2021). Food waste vs. food loss: Know the difference and help #StopTheWasteToday.


Assistant Professor and Extension Specialist
Poultry Science
Professor and Director, Marine Aquaculture Research Center
Biological & Agricultural Engineering

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Publication date: July 26, 2023

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