Effects Of Dietary Energy And Arginine Levels On Pork Quality And Lipid Metabolism Of Fininshing Pigs

The pork quality partly depends on the deposition of intramuscular fat (IMF). Energy and arginine (Arg) play an important role in lipid metabolism. Our hypothesis was that the intake of diets with different energy and Arg level may result in the differencial profile of lipid deposition, which could affect the pork quality. The present study was to investigate the effects of dietary energy and Arg levels on growth performance, carcass traits, meat quality and lipid metabolism of finishing pigs in a 2X2 factorial design. The main factors consisted of dietary digestible energy (DE) levels (control diet (C,14.22MJ/kg) and, high energy diet (HE, formulated by 10% coconut oil replaced 10% corn starch in control diet, 16.21MJ/kg)), dietaty Arg supplementation levels (0 and 1%). Sixty Duroc×Landrace× Large White (DLY) crossbred pigs were randomly divided into 4 treatments with 5 repli-cates per treatment and 3 pigs per replicate. After a 28-day trial period, a pig with aver-age-weight per replicate from each dietary treatment was selected to sample blood via the anterior vena cava. The serum was separated for analysis of Arg and lipid metabolism pro-files. Then, they were sacrificed to determine carcass traits and meat quality. At the same time, subcutaneous fat and longissimus dorsi muscle tissues were collected to measure li-pid metabolism-related gene expressions.(1) The average daily feed intake (ADFI, P<0.05) and ratio of feed to gain (F/G, P<0.01) of pigs in 16.21MJ/kg group were decreased compared with that of 14.22MJ/kg group. Arg supplementation had no effecton growth performance (P>0.05).(2) Dietary energy and Arg levels did not affect carcass traits (P>0.05).(3) The intake of HE diet significantly (P<0.01) increased shear force of longissimus dorsi muscle. Arg supplementation in HE group, but not in C group, significantly (P<0.05) decreased shear force. Compared with C group without Arg supplementation, the intake of HE without Arg supplementation decreased the intramuscular fat (IMF) content by 32.39% (P>0.05). However, Arg supplementation in HE increased IMF content by 51.33% (P>0.05)(4) Nitric oxide (NO, P<0.01), triglyceride (TG, P<0.05), total cholesterol (TC, P<0.01), high-density lipoprotein cholesterol (HDL-C, P<0.01) levels and nitric oxide synthase (NOS, P<0.01) activity enhanced, and low-density lipoprotein cholesterol (LDL-C) level tended (P=0.095) to increase, LDL-C/HDL-C in serum reduced (P<0.01) by dietary HE treatment. Arg supplementation significantly increased Arg (P<0.05) and NO (P<0.01) concentration, and NOS activity (P<0.01) in serum. Arg supplementation in C group, but not in HE group significantly enhanced NOS activity (P<0.01) and NO (P<0.01) level.(5) In subcutaneous fat tissue, the intake of HE diet significantly (P<0.01) down-regulated fatty acid synthase (FAS) mRNA expression. Arg supplementation signifi-cantly down-regulated acetyl-CoA carboxylase (ACC, P<0.05) and FAS (P<0.01) mRNA expressions, but significantly up-regulated carnitine palmitoyltransterase-1 (CPT-1, P<0.01) and hormone sensitive lipase (HSL, P<0.05) mRNA expressions. Arg supplementation in C group, but not in HE group significantly (P<0.01) down-regulated ACC and FAS mRNA expressions, and significantly (P<0.01) up-regulated CPT-1 and HSL mRNA expressions.(6) In longissimus dorsi muscle tissues, the intake of HE diet significantly (P<0.01) down-regulated peroxisome proliferator-activated receptor-y (PPAR-y) mRNA expression, and tended to down-regulated mRNA expressions of ACC (P=0.078) and FAS (P=0.082), but significantly (P<0.01) up-regulated CPT-1 and HSL mRNA expressions. Arg supple-mentation significantly (P<0.05) up-regulated PPAR-y mRNA expression. Arg supplemen-tation in C group significantly up-regulated FAS (P<0.05), PPAR-y (P<0.01), CPT-1(P<0.05) and HSL (P<0.01) mRNA expressions. Arg supplementation in HE group significantly (P<0.01) down-regulated HSL mRNA expression and had no effect on FAS, PPAR-y and CPT-1 mRNA expressions.These results indicated that increasing dietary energy level of fininshing pigs with coconut oil significantly decreased ADFI, F/G and muscle trenderness. However,1% Arg supplementation significantly attenuated the decrease of muscle trenderness caused by high energy diet. The mechanism of effects of dietary energy and Arg level on pork qual-ity may be closely related to the difference in lipid metabolism-related gene expressions. Coconut oil significantly down-regulated PPAR-y mRNA expression and up-regulated the mRNA expressions of CPT-1 and HSL. Moreover, Arg supplementation in high energy diet significantly down-regulated HSL mRNA expression.