Study tests fermented tomato pomace as soybean meal substitute

A newly published paper in Animals reports that fermented dried tomato pomace may be a workable substitute for soybean meal in Boer goat diets, with the most favorable results seen at a two-thirds replacement rate rather than full substitution. In a 60-day feeding trial involving 24 male Boer goats, researchers found no adverse effects on routine serum biochemical markers, total immunoglobulin, or alternative complement hemolytic activity across treatment groups, while identifying selective shifts in immune markers, antioxidant-related gene expression, and meat-quality traits. (mdpi.com)

The study lands in a broader context of feed-cost pressure, interest in alternative protein sources, and growing attention to agro-industrial by-products as livestock feed ingredients. Tomato pomace, made up largely of skins, seeds, and residual pulp from tomato processing, has drawn attention because it contains fiber, fat, and bioactive compounds including lycopene, tocopherols, carotenoids, terpenes, and polyphenols. Reviews published in recent years describe replacement of soybean meal with tomato pomace as an active research area, especially where producers are looking to reduce food-feed competition and improve by-product utilization. (frontiersin.org)

In the new goat study, the diets replaced soybean meal with fermented dried tomato pomace at 33.33%, 66.66%, and 100% inclusion levels. The authors reported that lysozyme activity increased linearly with higher fermented tomato pomace inclusion, while expression of immune-related cytokines shifted in a tissue-specific way, including increased IL10 and reduced IL1B and TNFα expression in selected tissues. In muscle, the 66.66% replacement group showed higher collagen content and lower cooking loss than the control and full-replacement groups, while the 100% replacement group had higher drip loss than the 66.66% group. Lipid oxidation during refrigerated storage changed over time, but not by treatment. (mdpi.com)

The transcriptomic component gives the paper more depth than a typical feeding trial. The investigators selected the 66.66% replacement group for exploratory hepatic comparison against controls and identified 587 differentially expressed genes. Enriched KEGG pathways were concentrated in metabolism and biotransformation, including steroid hormone biosynthesis, retinol metabolism, bile secretion, pentose and glucuronate interconversions, and xenobiotic metabolism. The paper also notes differentially expressed genes within PI3K-Akt, MAPK, NF-κB, and cytokine-cytokine receptor pathways, suggesting that the dietary shift may influence not just nutrient supply, but also cellular stress and immune signaling. (mdpi.com)

This isn’t the first signal that tomato pomace may have nutritional value in goats. Feed composition work published in Frontiers in Veterinary Science this year reported that tomato pomace contains more crude protein and ether extract than whole tomato, though still far less crude protein than soybean meal, underscoring why formulation and processing matter when it is used as a replacement ingredient. Earlier goat and ruminant literature summarized in Feedipedia and review papers suggests tomato pomace can sometimes replace a portion of soybean meal without harming intake or nitrogen utilization, but results vary by species, processing method, and inclusion rate. (frontiersin.org)

Expert reaction specific to this paper appears limited so far, but the surrounding review literature is fairly consistent: tomato pomace is promising, especially as a circular-economy ingredient, yet still needs more work on standardization and scale-up. One recent review explicitly says further research should focus on processing technology and large-scale application, while another notes that life-cycle assessments and species-specific evidence remain sparse. Separate reviews also caution that fruit and vegetable by-products can carry contaminant risks, including pesticide residues, making quality control essential before widespread adoption. (pmc.ncbi.nlm.nih.gov)

Why it matters: For veterinarians, nutritionists, and technical teams advising goat producers, the practical takeaway is that alternative protein strategies may deliver more than a feed-cost story. This paper suggests partial replacement with fermented dried tomato pomace could influence immune signaling and meat-quality outcomes without obvious short-term harm to standard blood chemistry. But it also reinforces a familiar point in ration design: more isn’t always better. The best outcomes here clustered around partial replacement, while full replacement appeared less favorable for some meat-quality measures. That distinction matters when translating experimental diets into on-farm recommendations for growth, carcass quality, and health monitoring. (mdpi.com)

What to watch: The next questions are whether these findings hold up in larger commercial herds, how fermented tomato pomace compares on cost per unit of usable protein, and whether regulators, feed manufacturers, or producer groups move toward clearer standards for nutrient consistency and contaminant testing in tomato-processing by-products used in small-ruminant diets. (pmc.ncbi.nlm.nih.gov)