Feed Additives Reshape Meat, Milk and Egg Quality, Review Finds

Feed additives have quietly become one of the most powerful levers in modern livestock production, and a new narrative review argues they can do far more than fatten animals. Published in Food Science of Animal Resources, the review synthesizes 82 peer-reviewed studies published between 2000 and 2025 and concludes that probiotics, prebiotics, enzymes, antioxidants, organic acids and phytogenic compounds can measurably improve the nutritional value, sensory attributes and oxidative stability of meat, milk and eggs, while extending shelf life by inhibiting microbial growth and lipid oxidation. The authors, Negasa Tamasgen and Mitiku Wamile, also caution that improper handling or overuse of these substances can harm animals and the environment, and that further research is needed to optimize dosing, address regulatory challenges and secure consumer acceptance.

The review’s search strategy was systematic in design even though the synthesis itself is narrative. The authors searched PubMed, Scopus, Web of Science and Google Scholar using Boolean combinations of terms such as “feed additives,” “probiotics,” “prebiotics,” “antioxidants,” “phytogenic compounds” and “organic acids” paired with “meat quality,” “milk quality,” “egg quality” and “shelf life.” The initial database search identified 723 records; after removing duplicates, 513 remained for screening, and following full-text review, 82 studies met the eligibility criteria. Studies were selected using a PICO framework covering livestock species including poultry, swine, cattle, goats and sheep, with a basal diet as the comparator and outcomes limited to nutritional composition, sensory attributes, oxidative stability, microbial safety and shelf life. Conference abstracts, case reports, in vitro studies and studies without a control group were excluded.

One of the review’s most technically significant contributions is its rejection of the simplistic natural-versus-synthetic dichotomy that dominates consumer discourse. Instead, the authors organize additives under the European Union’s Regulation (EC) No 1831/2003 into five functional categories: technological, sensory, nutritional, zootechnical, and coccidiostats and histomonostats. This framework matters because the same substance can serve different functions depending on dose and intent. Vitamin E, for example, functions as a nutritional additive at physiological levels but becomes a technological antioxidant at pharmacological doses. Propionic acid acts as a preservative at higher concentrations but as a gut flora stabilizer at lower doses. The classification determines authorization pathways, maximum residue limits and labeling requirements, making regulatory clarity essential for both researchers and practitioners.

Technological additives, the first category, include antioxidants, preservatives and emulsifiers. Antioxidants are the most extensively studied subgroup in the context of product quality. Natural sources such as vitamin E and plant-derived polyphenols, alongside synthetic alternatives like butylated hydroxytoluene and butylated hydroxyanisole, function primarily by intercepting free radicals through chain-breaking mechanisms or by chelating pro-oxidant metals such as iron and copper. The review reports that dietary antioxidants have been consistently associated with reduced metmyoglobin formation in fresh meat, delayed lipid peroxidation in dairy products and improved oxidative stability of egg yolks during storage. Preservatives such as formic and propionic acid inhibit mold and bacterial growth in feed materials, indirectly protecting product quality by reducing the risk of mycotoxin contamination, which can accumulate in animal tissues and milk.

Nutritional additives include vitamins, amino acids, trace elements and essential fatty acids. Vitamin E supplementation has been shown to reduce lipid oxidation, measured as thiobarbituric acid-reactive substances, by up to 40 percent in eggs stored at 4 degrees Celsius for 28 days, while in beef it delays myoglobin oxidation and preserves red color during extended aging. Vitamin D fortification of poultry diets can raise egg yolk vitamin D3 content to 150 to 200 international units per egg, meeting approximately 25 percent of the recommended daily intake for humans. Omega-3 sources such as flaxseed, fish oil and algae can increase EPA and DHA content in pork and chicken by two- to threefold, and oilseed supplementation in dairy cows boosts conjugated linoleic acid in milk. However, the review stresses that omega-3-enriched products are prone to oxidation unless stabilized with additional antioxidants, necessitating combined use of nutritional and technological additives.

Zootechnical additives, the third major category, work primarily through the gastrointestinal ecosystem. Probiotics such as Lactobacillus, Bacillus, Bifidobacterium and Enterococcus species modulate gut microbiota and competitively exclude pathogens. The review reports that probiotic supplementation has been shown to reduce Salmonella contamination in poultry meat and eggs, lower E. coli and Listeria in beef and pork, and improve milk hygiene by reducing mastitis-causing bacteria. Prebiotics such as fructooligosaccharides, mannanoligosaccharides and inulin promote gut health through selective fermentation by beneficial bacteria, producing short-chain fatty acids that lower intestinal pH. Mannanoligosaccharides additionally exert direct anti-adhesive effects by mimicking glycoprotein receptors on the intestinal epithelium, binding to type-1 fimbriae on pathogens such as Salmonella and E. coli and preventing their attachment to intestinal cells.

Organic acids deserve special attention because their antimicrobial mechanisms extend well beyond simple luminal acidification. The undissociated, lipophilic molecules diffuse across bacterial cell membranes and dissociate in the neutral pH of the cytoplasm, releasing protons that force bacteria to expend ATP through membrane-bound proton pumps to maintain internal pH homeostasis. This energy depletion, combined with anion accumulation that inhibits key metabolic enzymes and disrupts nucleic acid and protein synthesis, ultimately kills or disables the pathogen. Formic, acetic and propionic acids penetrate membranes efficiently due to their short chain length, while citric acid acts predominantly through luminal acidification and metal chelation. Combinations of different acids often exhibit synergistic effects, with lipophilic acids providing membrane penetration and hydrophilic acids providing luminal acidification and chelation.

A crucial methodological distinction the review emphasizes is the difference between in vivo effects and post-collection effects. In vivo mechanisms operate during the animal’s life, altering tissue composition through metabolic pathways. Omega-3 fatty acid supplementation increases incorporation of EPA and DHA into muscle tissue, milk fat and egg yolks, while organic selenium is incorporated into selenoproteins such as glutathione peroxidase that enhance antioxidant status within tissues. Vitamin E deposited in muscle cell membranes continues to exert protective effects after slaughter, reducing metmyoglobin formation and delaying lipid oxidation during refrigerated storage. Post-collection mechanisms, by contrast, involve treating harvested products directly. The review notes that the frequently cited two- to three-log reductions in Salmonella and E. coli from citric and lactic acids are predominantly demonstrated through direct application to meat surfaces via spraying, dipping or vacuum-infusion, not through dietary supplementation alone.

The review also addresses milk shelf life with unusual precision, separating udder health from product longevity. A meta-analysis of randomized controlled trials demonstrated that oral probiotics reduce the incidence of mastitis during lactation and significantly reduce bacterial counts in milk for mastitis patients. Certain probiotic strains may also reduce somatic cell count, an indicator of udder inflammation. However, the authors caution that a reduction in mastitis incidence or somatic cell count does not automatically translate to an extension of milk shelf life. Milk shelf life is primarily determined by total bacterial load at collection, cold chain integrity, processing conditions and enzymatic activity, particularly plasmin and bacterial proteases and lipases. The psychrotrophic bacteria Pseudomonas and Bacillus species, which are the primary agents of milk spoilage during refrigerated storage, are not necessarily reduced by targeting mastitis-causing pathogens alone.

The review concludes that feed additives significantly improve livestock product quality and shelf life by modulating gut health, reducing oxidation and inhibiting microbial growth, but it stops short of declaring the problem solved. The authors note that few studies provide comprehensive economic analyses, that some phytochemicals have dose-dependent negative effects on growth performance, and that the efficacy of natural alternatives can vary depending on the type of phytochemical, the dosage and the animal species. They call for dose-response studies, investigations of synergistic effects between additives, and development of nano-encapsulation technologies, alongside regulatory reforms that recognize the multiple benefits of antioxidants and other feed additives. For an industry under pressure to reduce antimicrobial resistance and meet consumer demand for natural products, the message is clear: the science is promising, but the optimization work has only begun.

Subject of Research: How feed additives affect the quality and shelf life of meat, milk and eggs

Article Title: Effect of feed additives on livestock product quality and shelf life: a narrative review

Article References: Tamasgen, N., & Wamile, M. (2026). Effect of feed additives on livestock product quality and shelf life: a narrative review. Food Science of Animal Resources, 46(1), Article 111. https://doi.org/10.1007/s44463-026-00113-5

Image Credits: AI Generated

DOI: 10.1007/s44463-026-00113-5

Keywords: feed additives, livestock, meat quality, milk quality, egg quality, shelf life, probiotics, antioxidants, organic acids, phytogenic compounds, omega-3 fatty acids, animal nutrition