This paper reviews current knowledge on two feedstuffs, that is, insect meal and fish by-products, as alternatives to conventional animal protein sources. After an introductory part that highlights the need for sustainable development of animal production, the alternative protein sources are discussed. In particular, after providing some indications on their production and supply focussing on EU, a SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis was performed to identify the key factors that could help or impair the development of both protein sources production sectors. Finally, future perspectives are presented. The use of processed animal proteins derived from insects in farmed fish feeding is recognised by the EU legislation that authorises the use of proteins from seven insect species and the allowed substrates to rear insects. Insects have several advantages in nutritional value and the amino acid composition of their proteins generally meet animal requirements for good growth and health. The SWOT analysis indicated that insect meals can be considered as feed functional ingredients with beneficial properties that depend on the insect species, rearing system adopted, and the substrate used for their growth. Insects are expected to be increasingly used as a replacement for conventional animal-derived proteins, especially in aquafeeds. In the section regarding fishery and aquaculture by-products, the potential use of raw materials obtained during seafood processing is discussed. Peptides and amino acids recovered from as hydrolysed proteins can be used in animal feeds to partially substitute conventional protein feedstuffs thus providing nutrients, bioactive compounds and feed additives for animals. The SWOT analysis identified opportunities and weaknesses. Both the alternative protein sources are promising alternative feed ingredients for livestock production.

The expected future demand for highly nutrient animal food products will push the animal production system to search for new sources of high-quality protein feedstuffs. In this scenario, economic and environmental issues will have to be considered while reducing the competition with the plant-based human food chains. Legume grains and some oilseed cakes, by-products from the oil industry, are the main protein sources for ruminants and terrestrial monogastrics such as pigs and poultry. Their relevant role will hold in the next decades, but it is necessary to increase the diversification of sources that can be grown profitably throughout the world, including European countries. Microalgae are a promising source of protein and other nutrients for animal feeding. However, an amazing richness of biologically active substances makes these organisms very interesting as feed ingredients, as their role go far beyond the supply of nutrients. Due to the limited usage of microalgae as human foodstuffs or food ingredients, low competition between microalgae-based feed and food chains is predictable. This review aims to synthesise current knowledge on minor pulses and other protein-rich plant products and microalgae, as alternative ingredients to the conventional animal protein sources, focussing on their production, availability, and nutritional values. Points of strength, weakness, opportunity and threat related to the use of these protein sources in animal feeding are separately analysed through a SWOT approach to underlie future needs in terms of research and/or technological development that could help valorise these nutrient sources as feed ingredients.

Proteins of animal origin represent physiologically active components in the human diet; they exert a direct action or constitute a substrate for enzymatic hydrolysis upon food processing and consumption. Bioactive peptides may descend from the hydrolysis by digestive enzymes, enzymes endogenous to raw food materials, and enzymes from microorganisms added during food processing. Milk proteins have different polymorphisms for each dairy species that influence the amount and the biochemical characteristics (e.g., amino acid chain, phosphorylation, and glycosylation) of the protein. Milk from other species alternative to cow has been exploited for their role in children with cow milk allergy and in some infant pathologies, such as epilepsy, by monitoring the immune status. Different mechanisms concur for bioactive peptides generation from meat and meat products, and their functionality and application as functional ingredients have proven effects on consumer health. Animal food proteins are currently the main source of a range of biologically-active peptides which have gained special interest because they may also influence numerous physiological responses in the organism. The addition of probiotics to animal food products represent a strategy for the increase of molecules with health and functional properties.

The aim of this study was to understand the relationship between changes in postmortem degradation of myofibrillar proteins and tenderness development in 3 different muscles from 10 Podolian young bulls aged 1, 7, 14, and 21 d. Psoas major (PM), longissimus dorsi (LD), and semitendinosus muscle (STD) were removed from each half carcass 24 h postmortem. Meat chemical composition, Warner–Bratzler shear force (WBSF), myofibril fragmentation index (MFI), total collagen content, and changes in myofibrillar proteins were estimated in triplicate at each aging time. A significant muscle effect was found on meat chemical composition. Semitendinosus muscle showed the lowest intramuscular fat percentage (P < 0.01) and the highest total collagen content (P < 0.01) with respect to LD and PM. Warner–Bratzler shear force decreased during aging in all muscles (P < 0.001), and semitendinosus was the toughest muscle whereas PM was the most tender (P < 0.001). Myofibril fragmentation index significantly increased (P < 0.001) in LD and PM meat throughout aging time whereas in semitendinosus it increased from 14 d of aging. Proteolysis was investigated by SDS-PAGE, western blotting, and 2-dimensional electrophoresis. Throughout postmortem aging, some structural proteins changed in intensity in all muscles analyzed. The blotting profile highlighted that desmin and troponin-T (TnT) bands were affected by both muscle and aging effects. Desmin degradation was more intense and faster in LD muscle than in semitendinosus and PM muscles. A progressive increase of the degraded isoforms of TnT (33 and 30 kDa polypeptides) was found during aging in LD, while, in PM these bands appeared earlier showing a greater intensity from 1 d. During aging, 2-dimensional gel electrophoresis (2DE) image analyses results showed a significant increase of the total number of spots reaching the highest value in the LD muscle at 21 d of aging (P < 0.01). Proteins separation also revealed differences in the spot number and expression patterns of myosin light chain (MLC) isoforms among muscles. A principal components analysis applied to meat chemical composition, tenderness, and myofibrillar proteins accounted for approximately 96.09% of total variance. Data highlight that aging affects the meat tenderness and proteolysis with different intensities in each muscle. These results provide knowledge about the tenderness mechanism in different muscles from a rustic breed and could be useful for the development of muscle specific strategies for improving the quality and value in different commercial cuts. Copyright © 2015. American Society of Animal Science .