Effects of dietary oxidized oil on laying performance, lipid metabolism, and apolipoprotein gene expression in laying hens

We studied the effects of dietary oxidized oils on serum lipid metabolic indices, estradiol level, and the gene expression of apolipoprotein B-100 and apolipoprotein VLDL-II in laying hens. Hy-Line Grey hens (280 +/- 10 d old; average egg production, 90.0 +/- 2.5%) were allotted to 1 of 4 dietary treatments, which were supplemented with 0 (control group), 1% (low oxidized group), 2% (moderately oxidized group), or 4% (highly oxidized group) thermally oxidized soybean oil. Each treatment contained 6 replicates, with 12 birds each. The feeding trial lasted for 30 d. Laying performance data were recorded weekly. Other indices were measured on d 0, 2, 6, 14, and 30 of the feeding trial. Hens in the moderately and highly oxidized groups had significantly lowered feed conversion ratios (P < 0.05). Those in the highly oxidized group also had decreased concentrations of serum very low density lipoprotein cholesterol on d 30 (P < 0.05) compared with the very low density lipoprotein cholesterol of hens in the moderately oxidized group. Hens in the moderately oxidized group had significantly increased expression of apolipoprotein B-100 (P < 0.05) from d 6 to 30. Consequently, hepatic triglyceride increased in this group on d 30 (P < 0.05). Serum triglyceride decreased in the moderately oxidized group on d 30 (P < 0.05), which may have been caused by the activation of peroxisome proliferator-activating receptor a. Serum estradiol levels were not significantly affected by oxidized oils at any time of measurement, but were significantly different between d 0 and 30 within the moderately oxidized group. This fact indicated that the effect of oxidized oils on apolipoprotein B-100 might partially be a cumulative result of the increasing secretion of estradiol. The results suggested that oxidized oil may affect the performance of laying hens through the regulation of apolipoproteins and estradiol.