ISSUE FOCUS 48 FEED & ADDITIVE MAGAZINE June 2025 lower levels of soybean meal. Highly digestible protein sources are used in place of soybean meal, along with the addition of synthetic amino acids (AA) to ensure essential AA requirements are met. 2. Mycotoxins Fungal-derived mycotoxins are common contaminants of feed that affect gut permeability and functioning. Whereas aflatoxin in feed is routinely monitored and levels tightly regulated worldwide, this is not the case for other mycotoxins. Fumonisin, deoxynivalenol (DON) and zearalenone (ZEN) are all common in feed in Asia and can have direct and synergistic effects on the expression and function of tight junction proteins in intestinal epithelial cells. This impairs gut barrier integrity, allows the ingress of more mycotoxins and facilitates pathogen invasion.2,3 Studies of DON have shown that it: • Activates T lymphocytes in porcine epithelial cells leading to increased expression of inflammatory cytokines.4 This inflammatory response is nutrient-demanding and redirects nutrients away from growth. • Reduces porcine reproductive and respiratory syndrome (PRRS) vaccination efficacy by impairing the antibody response. This effect is seen at 2.5 to 3.5 mg of DON/kg.5 • Predisposes piglets to porcine epidemic diarrhoea virus (PEDV) which causes acute diarrhoea and impaired growth. This effect is seen at or above 750 µg DON/kg.6 In addition, in vitro studies have shown that aflatoxin B1 can reduce expression of the vitamin D receptor, potentially impairing vitamin D signaling important for bone health. 3. Peptidoglycans Peptidoglycans are a major component of bacterial cell walls. They contain lipoproteins that are recognized as foreign by piglet immune system. This causes an inflammatory response7 which is nutrient-demanding and therefore redirects nutrients away from growth. Peptidoglycans can also act as a physical barrier in the gut, directly reducing the absorption of nutrients which impacts on growth.8 4. Undigested nutrients a. Crude protein Soybeans and other legumes contain protease inhibitors—such as the Kunitz and Bowman-Birk types—that impair protein digestion by blocking enzymes like trypsin and chymotrypsin. This leads to more undigested protein in the gut, promoting proteolytic fermentation and the production of toxic nitrogenous metabolites (e.g., ammonia, amines), which contribute to diarrhoea and reduced feed efficiency. Over time, these effects can disrupt gut health and immune function. Heat treatment reduces inhibitor activity, but excessive heating should be avoided as it can impair energy and amino acid digestibility through Maillard reactions, particularly affecting lysine availability. Photo: dsm-firmenich
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