Due to the increasing demand for alternative protein feed ingredients, the utilization of oilseed by-products in animal nutrition has been sought as a promising solution to ensure cheap and environmentally sustainable feedstuffs. This review aimed to summarize the nutritional value of six cold-pressed cakes (rapeseed, hempseed, linseed, sunflower seed, camelina seed, and pumpkin seed) and the effects of their inclusion in diet for ruminant, pig, and poultry on nutrient digestibility, growth and productive performance, and quality of the products. The presented results indicated that these unconventional feed ingredients are a good protein and lipid source and have a balanced amino acid and fatty acid profile. However, contradictory results of animal production performances can be found in the literature depending on the cake type and chemical composition, dietary inclusion level, animal category, and trial duration. Due to the substantial amount of essential fatty acid, these cakes can be efficiently used in the production of animal products rich in n-3 and n-6 polyunsaturated fatty acids. However, the utilization of cakes in pig and poultry nutrition is limited because of the presence of antinutritive factors that can deteriorate feed intake and nutrient utilization.

Food waste and feed-food competition can be reduced by replacing traditional feed ingredients such as cereals, with former food products (FFPs) in livestock diets. These foodstuffs, initially intended for human consumption, are recovered, mechanically unpacked, and then ground. Despite this simple and inexpensive treatment, packaging contaminants (remnants) are often unavoidable in the final product. To maximize the exploitation of FFPs and to minimize the associated risks, packaging remnants need to be quantified and characterized. This study tested the efficacy of the Fourier Transform Infrared Spectroscopy coupled with an optical microscope (μFT-IR) in identifying packaging remnants in 17 FFP samples collected in different geographical areas. After a visual sorting procedure, presumed packaging remnants were analyzed by μFT-IR. The results showed significant differences (p < 0.05) between the FFPs in terms of the total number of foreign particles found (plastics, cellulose and aluminum remnants, ranging from 4 to 19 particles per 20 g fresh matter), and also regarding the number of cellulose and aluminum particles. These data clearly demonstrate the need for sensitive instruments that can characterize the potential contaminants in the FFPs. This would then help to reduce the overestimation of undesirable contaminants typical of simple visual sorting, which is currently the most common method.