| Sumario: | Two experiments were performed to assess the effect of different amounts of dietary polyunsaturated fatty acids (PUFA) on fatty acid composition of chickens. The contribution of endogenous fatty acid synthesis to fatty acid profile w as also estimated In trial I, different fat sources were blended in d i fie re n t ratios allowing a gradient of dietary PUFA (from 15 to 61 g'kg), keeping added fat level constant (9%). In trial 2, PUFA-rich oil was added in increasing inclusion levels (2, 4, 6 and 8 %), achieving a dietary PUFA content ranging between 27 and 59 g kg.. Increasing dietary PUFA inclusion resulted in an increase of PUFA deposition, with higher efficiency when dietary fat also provided saturated (SFA) and monounsaturated (MUFA) fatty acids (trial 1) Increasing dietary PUFA in both trials resulted in a decrease of SFA and MUFA concentration in the whole body. The estimated deposition of fatty acids front endogenous synthesis is reduced when dietary fat increases from 0 to 10%, varying between 35.34 % and 17.66 % for SFA; and between 52.70 To and 7.01 % for MUFA in the whole body. The higher variation range for the MUFA supports the existence of a mechanism maintaining lire SFA: (MUFA+PUFA) ratio inside a specific range in biological membranes.
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