Alternative Protein Sources in Poultry and Pig Nutrition—A Review

Proteins are an essential nutrient for the viability of all animals, enabling organisms to grow, regenerate and defend themselves against pathogenic organisms. Soybean and soybean-based materials are commonly used to supplement protein in animal nutrition. However, soybeans are among the most expensive ingredients in feed mixtures, and the expansion of their planting areas has led to rainforest deforestation. Soybean cultivation is also associated with soil degradation, extensive use of chemicals and fossil fuels and global warming. This is partly because soybeans are grown primarily in specific regions of the world and therefore must be transported over long distances. This is a costly process that has a significant negative impact on the environment and does not meet sustainability requirements. At the same time, global population growth is increasing protein consumption, putting even more pressure on the environment. It is therefore necessary to look for different alternative feeds that could replace soybeans or at least reduce their dominance in the feed supply. Several studies mention new non-traditional feeds that could help solve this problem. This review provides an overview of available information on alternative protein sources and their use in poultry and pig nutrition, thereby assisting in their selection. The characteristics of selected alternative protein feeds (such as insects, algae, lupine, peas, faba beans, single-cell protein and nettle) and their effects on the performance or health parameters of the animals mentioned are described below.