Tolerability of graded levels of tall oil fatty acids as a nutritional additive for broiler chickens: a 45-day target animal safety study.

1. The following study was conducted to evaluate the tolerability of tall oil fatty acid (TOFA) to broiler chickens, at three graded levels as a nutritional additive in complete feed.2. 256 one-day-old female and male Cobb 500 broiler chickens were assigned to four dietary treatment groups with TOFA at 0 (control), 1.0, 3.0, or 5.0 g/kg within a complete feed for 45 d.3. Birds were weighed individually on days 0, 16, 31 and 45, and the feed intake, bird weight gain, and feed conversion ratio were calculated for the respective starter, grower and finisher phases and over the whole study. On day 45, blood samples were drawn from each bird for haematology and blood chemistry measurements. Two birds per pen were subjected to gross pathological examination and sampling of several tissues for histopathology, including weighing the liver.4. The dietary treatments did not affect zootechnical performance variables or mortality over the whole study period. Bird performance was typical for the breed.5. Haematology, clinical chemistry and histopathology did not reveal any changes associated with dietary TOFA dosing. However, the 5.0 g/kg dose level increased the relative weight of the liver, as a percentage of final body weight, compared to the control group, but there was lack of corresponding histopathology findings.6. In conclusion, the study indicated that oral administration of TOFA for 45 d in feed was well tolerated by the birds at dietary levels of up to 5.0 g/kg.