Effects of Olive Leaf and Marigold Extracts on the Utilization of Nutrients and on Bone Mineralization using Two Different Oil Sources in Broilers

The aim of this study was to investigate the effects of olive leaf and marigold extracts on the apparent total tract digestibility (ATTD) of the principal nutrients and energy, as well as on mineral utilization (Ca, P, Mg, Mn, Fe, Cu and Zn) in relation to bone characteristics in broilers fed walnut- or linseed oil-supplemented diets. Thirty-six 12-day-old commercial broilers Ross 308 were reared in metabolic cages, assigned to one of the six dietary treatments (3 × 2 factorial design): three supplements (not supplemented, olive leaf extract, or marigold extract), and two oils (walnut or linseed oil). The results showed that the marigold extract reduced Zn and P balances and tended to lower the balance of ash and Mg, and the ATTD of Zn and Mg. Diets with linseed oil increased the ATTD of acid detergent fiber and reduced the ATTD of the organic residue and Cu. No differences in the bone characteristics of tibia were observed between treatments. These results indicated that the inclusion of marigold extract had a negative effect on the Zn and P balance, and that neither extract had any major effect on the digestion and utilization of energy and other investigated nutrients, or on bone mineralization, irrespective of the oil source included in the diet.