Effect of dietary energy source on deposition and fatty acid synthesis in the liver of the laying hen

1. This experiment was conducted to determine the effect of different dietary energy sources on hepatic lipid deposition and fatty acid synthesis in the layer's liver. 2. A total of 120 Lohmann Pink commercial layers were divided into three groups of 40 birds each and restricted-fed so that they had similar metabolisable energy intakes. Experimental diets were prepared as follows: (1) maize-soybean meal basal diet (CS) fed at 108 g/d, (2) soybean isolated protein plus lard diet (SL) fed at 63 g/d, (3) soybean isolated protein plus maize starch diet (SC) fed at 94·4 g/d. All feed intakes were limited so that the birds consumed similar quantities of the major nutrient daily; all the birds were fed 4 times/d. 3. Compared with chicks fed on the CS and SC, hepatic EE (ether extraction) and triglyceride of the SL group were increased significantly and the total of cholesterol and phospholipids was increased. However, there were no significant reductions in plasma VLDL and ApoB100 concentrations. 4. The birds fed on the maize starch diets up-regulated srebp-1c and chrebp mRNA transcription levels significantly. The maize starch diet also increased the activity of acetyl CoA carboxylase (ACC) and fatty acid synthase (FAS) significantly. However, the lard diet led to a decrease of ACC activity, but had no significant effect on FAS. 5. These results showed that dietary carbohydrates can induce hepatic lipid deposition by increasing the ACC and FAS activities and up-regulating the srebp-1c and chrebp mRNA transcription levels in the layer's liver much more readily than dietary fat, and layers fed on high carbohydrate diets tend to have more fatty livers.