Abstract
Tall oil fatty acids (TOFA) are novel, health-improving feed ingredients which have been shown to improve the performance of broiler chickens. TOFA contains resin acids, the suggested key components for its beneficial effects. For product safety, possible accumulation of TOFA components in tissues consumed by end-users is an issue of major importance. Wheat-soy-based diets with an indigestible marker and TOFA at 0, 750 and 3,000 g/t were fed to broiler chickens for 5 weeks; 11 replicate pens/treatment. Deposition of resin acids was assessed by analyzing jejunal tissue, breast muscle, abdominal fat, blood, liver, bile, and digesta along the intestinal tract at the end of the 35-day trial. Both free and conjugated resin acids were quantified. With TOFA 3,000 g/t diet, 30% of ingested resin acids could not be recovered from jejunal digesta. Also, a proportion representing 45% of resin acids fed were in conjugated form and thus had already re-entered the intestine from the bile duct. This means that at least 75% of resin acids ingested had become absorbed in, or proximal to jejunum. Recovery of resin acids in excreta was 45 and 70% when TOFA was fed at 750 and 3,000 g/t, respectively. Based on recovery data, of the estimated 1,087 mg of resin acids ingested by birds on the high TOFA dose during their lifetime, about 330 mg was unaccounted for. In analysis of jejunal tissue, blood, liver, bile, breast muscle, and abdominal tissue, <1 mg of resin acids was found after the 35-day trial when TOFA at the 4-fold the recommended dose was fed. It is likely that the host or microbiota mineralized or converted one-third of resin acids to a form that escaped analysis. TOFA at 3,000 g/t dose caused no detectable adverse effects in broiler chickens. Based on analysis of breast meat and liver, the common edible tissues, a human consumer would ingest <100 μg of resin acids in a single meal. That is one-thousandth of the dose shown to be harmless in rodents. Thus, unintentional exposure of human consumers to resin acids is marginal, and posed no safety concerns.
Highlights
The ban on antibiotic growth promoters in an increasing number of countries worldwide has given rise to an intensive search for new products to improve animal performance and health
The broiler chicken groups were fed the control diet or a diet supplemented with tall oil fatty acids (TOFA) at 750 or 3,000 g/t for 5 weeks
The results showed that the residual concentration of both abietic acid and dehydroabietic acid increased with the increasing rate of TOFA inclusion in the diet (Figure 1)
Summary
The ban on antibiotic growth promoters in an increasing number of countries worldwide has given rise to an intensive search for new products to improve animal performance and health. One new additive used to improve performance and health in production animals is tall oil fatty acids (TOFA), a high-volume side-product from the wood processing industry. It is derived from coniferous trees in the Kraft process, where acylglycerols are hydrolyzed under alkaline conditions into free fatty acids and glycerol, acidified and eventually distilled to produce the final TOFA product [1]. Resin acids are tricyclic diterpenoids, the most abundant of which in the TOFA product used here were abietic acid, dehydroabietic acid, and palustric acid. These three specific acids accounted for 53.5% of total resin acids in the product
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