AbstractLipids (fats and oils) are concentrated source of energy in poultry diets that improves palatability, feed consistency, provides essential fatty acids and increases the absorption of fat-soluble vitamins. Fresh oil is an expensive energy source and its exposure to air, heat, metallic catalyst during storage and processing may lead to its oxidative deterioration. This review highlights the response of modern poultry to dietary oxidized oil on growth performance, nutrients digestibility, gut health, carcass characteristics, meat quality, blood chemistry and tissue oxidative status. Literature shows that in moderately (peroxide value (PV): 20 to 50 meq kg−1) and highly (PV: 50 to 100 meq kg−1 or above) oxidized oils, lipid peroxidation causes rancid odours and flavours that negatively affect feed palatability, reduces intestinal villus height that decreases the surface area available for nutrients absorption. The oxidation products also damage fat soluble vitamins (A, D, E and K) in blood resulting in an oxidative stress. The use of oxidized oil in poultry diets has no significant effect on dressing percentage, pH and meat colour, whereas carcass weight decreases and drip loss of meat increases. Overall, there is a contradictory data regarding the influence of oxidized oil in poultry feed depending on the PV and inclusion levels. The reviewed literature shows that the use of mildly oxidized (PV < 20 meq kg−1) oil in poultry feed with 4 to 5% inclusion level decreases the feed cost and ultimately cost of poultry production without compromising their growth performance. It can, therefore, partially replace fresh oil as an efficient, cost effective and sustainable energy source in poultry diets.

The impacts of dietary levels of oxidized vegetable (sunflower) oil on growth performance, gut morphology, nutrients utilization, serum cholesterol and meat fatty acid profile were evaluated in Ross 308 straight-run (n = 192) day-old broilers. The broilers were arbitrarily distributed among four dietary treatments including; FVO: fresh vegetable oil (1 mEq kg−1), LOO: low oxidized (20 mEq kg−1), MOO: moderately oxidized (40 mEq kg−1), and HOO: highly oxidized vegetable oil (60 mEq kg−1) with 5% inclusion containing six replicates. Results revealed that the broilers consuming MOO and HOO based diets showed reduced (p = 0.05) feed intake, body weight gain and carcass weight accompanied by a poorer feed conversion ratio than those consuming FVO. Villus height, villus height to crypt depth ratio, ileal digestibility of crude protein (p = 0.041), crude fat (p = 0.032) and poly unsaturated fatty acids (p = 0.001) in thigh muscles were decreased, whereas crypt depth (p = 0.001), serum cholesterol levels (p = 0.023) and short chain fatty acids (p = 0.001) were increased (p < 0.001) by increasing dietary oxidation level. In conclusion, MOO and HOO exerted deleterious effects on growth, carcass weight, gut development and nutrients utilization. Low oxidized vegetable oil (20 mEq kg−1), however, with minimum negative effects can be used as a cost effective energy source in poultry diets.