Effects Of Different Energy Source On Lipid Metabolism And Laying Performance Of Layers

This study was to inveati(?) the effects of lard or cornstarch as main dietary energy source on lipid metabohsm and laying performance oi laying hens, and whether supplementation of metformin, a regulator of lipid metabolism, couid regulate these effects. A total of 120 Lohmann brown-shell laying hens were randomly assigned to 5 dietary treatments. Each treatment had 8 replicates (cages) with 3 hens each. Control group was fed com-soybean meal practical diet. Experimental diets consisted of isolated soybean protein as only protein source and lard or cornstarch as main energy source with or without supplementation of metformin. All layers consumed same amount of nutrients. Metformin was fed at 0.55g per day per bird. The experiment was lasted for 8 weeks. At the end of experiment, one bird from each replicate was sacrificed to collect plasma, liver and ovary sample for measurements of ether extract (EE) in the liver. expression of oocyte vitellogenesis receptor (OVR) in the ovary and Apo(?) coment in plasma. Results showed that laying rate was significantly decreased by 51.55%,13.6%,59.87% and 38.63% for lard, cornstarch or lard+metformin, cornstarch+metformin group in comparison to control group respectively. Compared with control group, hepatic EE content was significantly higher for lard (P=0.023) or cornstarch (P=0.000), but plasma triglyceride and cholesterol contents were not significantly different. Metformin supplementation had no effects on hepatic EE and cholesterol contents, but decreased plasma triglyceride concentration. Plasma ApoB content, VLDL level and OVR expression were slightly lower for lard or cornstarch group. Plasma ApoB content (P=0.015, or 0.020), VLDL level (P=0.016, or 0.011) and OVR expression (P=0.021, or 0.037) were significantly lower for lard+metformin or cornstarch+metformin group. Lard supplementation could significantly lowered yolk EE (P<0.01) but had no effect on yolk TG, TC. and phospholipids. Yolk TG level was the lowest and yolk EE was decreased for cornstarch group, but yolk TC and phospholipids contents were not Significantly different. Yolk EE (P<0.01) and TC (P<0.05) contents were decreased for two metformin groups Lard and cornstarch significantly increased yolk oleic acid (P<0.01).(?),lowered volk linoleic acid (P<0.01) and the level was the lowest for cornstarch group. Concldsi(?)n (?) cornstarch as main dietary energy somce could alter lipid metabolism towards the excessive deposition of hepatic lipid and depress laying performance for laying hens with lard being greater extent.2) Lard or comstarch could alter adversely transportation and deposition of lipid, lard group had worse effect.3.) The meiformin supplementation could alleviate excessive deposition of hepatic lipid, but affect adversely laying rate.