Inaugural ASAS–CAAV Asia Pacif ic Rim Conference Abstracts

103 Use of natural antimicrobials to improve the control ofbacterial pathogens in cured processed meats manufactured without directaddition of nitrite. Y. Xi* 1,2 , J. G. Sebranek 2 , G. H. Zhou 1 , G. A. Sullivan 2 , A.L. Jackson 2 , and K. D. Schrader 2 , 1 Nanjing Agricultural University, Nanjing,Jiangsu, China, 2 Iowa State University, Ames, IA, USA.Growing concern among consumers about nitrite in processed meats has createddemand for natural products without preservatives. In order to meet demandfor what are labeled as uncured products while retaining typical cured meatproperties, processors have begun manufacturing these products by addingnatural ingredients, usually vegetable powder, that are high in nitrate. Bacterialreduction of nitrate provides the nitrite required for a typical curing reaction.However, in this case, there is less control of the amount of nitrite. Due to theregulatory requirement that no direct addition of nitrate or nitrite is permitted,increased growth of foodborne pathogens is likely. Because of this concern,several commercial brands of meat products (frankfurters, hams, bacon)manufactured without direct addition of nitrite or nitrate were challenged withinoculations of Clostridium perfringens and Listeria monocytogenes to assesspathogen growth. Reduced C. perfringens and L. monocytogenes inhibition(P < 0.05) was observed in the majority of the commercial uncured meatproducts when compared to controls. To evaluate the potential for additionalantimicrobial controls for these processed meats without direct addition ofnitrite, several natural compounds have been studied. A meat model systemcontaining 80:20 lean:fat boneless pork, 2% salt, and 10% water was preparedwith 200 ppm/150 ppm ingoing nitrite plus lactate and diacetate or with otherselected natural inhibitors. The meat was placed in beakers and cooked to aninternal temperature of 71°F. A 5-strain mixed L. monocytogenes culture wassurface-inoculated at 4 log into the system. Results have shown that nitriteplus lactate and diacetate suppressed L. monocytogenes, by 3 to 5 log cfu/gat 10°F on d 12. A 2 to 4 log reduction of L. monocytogenes was observedby cranberry powder by d 9. Other natural ingredients such as cherry powder,lemon powder, and grape seed extract also demonstrated 0.5 to 2.0 log reductionof L. monocytogenes. Similar results for frankfurters produced at Iowa StateUniversity were observed.Key Words: natural antimicrobial, pathogen control, cured processed meat104 The effects of dietary conjugated linoleic acid on thegrowth performance and muscular nutrient of three duck breeds. Z. S.Xia* 1 , L. Chen 1 , R. C. He 2 , Y. Y. Liao 2 , and Y. F. Lu 2 , 1 College of Animal Scienceand Technology, Guangxi University, Nanning , Guangxi, P. R. China, 2 AnimalHusbandry Institute of Guangxi, Nanning, Guangxi, P. R. China.Tuesday, November 10, 2009SYMPOSIA AND ORAL SESSIONSMeat Safety Symposiumdecreased by CLA supplementation (P < 0.01). (5)The CLA content in breast andthigh muscle of 3 duck breeds significantly increased by CLA supplementation(P < 0.01). In summary, there were no significant differences in ADG betweenCG and TG for the 3 duck breeds. Dietary CLA significantly increased serumTC of JXD (P < 0.05), but it did not significantly influence serum lipids of CVDand MD. Dietary CLA significantly increased CLA deposition in muscle of 3duck breeds.Key Words: duck, conjugated linoleic acid, muscular nutrient105 Leucine promotes leptin receptor expression in mouseC2C12 myotubes through the mammalian target of rapamycin pathway.X. Mao*, X. Zeng, and S. Qiao, State Key Laboratory of Animal Nutrition,College of Animal Science and Technology, China Agricultural University,Beijing, China.Leptin plays a critical role in regulating muscle protein metabolism by bindingwith leptin receptors in a 1:1 stoichiometry. Leucine has been shown tostimulate leptin production in adipose tissue and adipocytes. However, the roleof leucine in the regulation of leptin receptor production in muscle is largelyunexplored. In the present study, the effect of leucine treatment on leptinreceptor levels in C2C12 myotubes was examined. Mouse C2C12 myoblastswere grown to 90% confluence and then induced to differentiate into myotubesusing DMEM/F12 medium containing 2% horse serum and antibiotics for 3d. Prior to the beginning of all experiments, the myotubes were starved for 12h in serum and antibiotic-free DMEM/F12 and all experiments were carriedout in this starvation medium. After different periods or different doses ofleucine incubation, the myotubes were collected to examine mammalian targetof rapamycin (mTOR) phosphorylation state and the levels of leptin receptorand β-actin by Western blot. Leucine stimulated leptin receptor productionin C2C12 myotubes in a dose-dependent manner and production peaked 2 hpostsupplementation. Leucine also stimulated the phosphorylation of mTOR.Rapamycin, an inhibitor of mTOR, completely suppressed leucine-inducedactivation of mTOR and significantly inhibited leucine-stimulated leptinreceptor production. Furthermore, after measuring the abundance of specialmRNA by quantitative real-time PCR, leucine increased abundance of theleptin receptor mRNA in C2C12 myotubes. These results suggest that leucinecontrols leptin receptor expression in mouse C2C12 myotubes via the mTORsignaling pathway and leptin receptor mRNA levels.Key Words: leptin receptor, leucine, mammalian target of rapamycinThis study was conducted to investigate the effects of dietary supplementationwith CLA on the growth performance and muscular nutrients of 3 duckbreeds. Seven-day-old Mule ducks (MD), Cherry Valley ducks (CVD), andJingxi ducks (JXD) were selected. Each breed had 60 ducks .Every breed wasrandomly assigned to control group (CG) and test group (TG), respectively. TheCG was given the basal diet, and the TG was fed the diets added to 1% CLAfor 49-d feeding trial. The results showed the following. (1) There were nosignificant differences in ADG of the 3 duck breeds between CG and TG (P >0.05), whereas dietary CLA significantly decreased the daily feed intake of MD(P < 0.05) and decreased the G:F of CVD (P < 0.01). (2) For MD, CP, Arg, andstearic acid (SA) in breast muscle and Glu, Gly, Ala, Val, Leu, Tyr, Lys, and SAin thigh muscle significantly increased (P < 0.05); linoleic acid (LA) in breastmuscle and Thr, Ser, Ile, Phe, and Arg in thigh muscle extremely significantlyincreased (P < 0.01); oleic acid (OA) and arachidonic acid in thigh musclesignificantly decreased by CLA supplementation (P < 0.01). (3)For CVD, SAcontent in breast and thigh muscle significantly increased (P < 0.01) and LA,eicosatrienoic acid (EA), and arachidonic acid content in breast muscle andether extract and linolenic acid (LNA) in thigh muscle significantly decreasedby CLA supplementation (P < 0.05). (4)For JXD, serum total cholesterol(TC), SA content in breast muscle, and Val and Ile content in thigh musclesignificantly increased (P < 0.05); LA content in breast muscle and SA contentin thigh muscle significantly increased (P < 0.01); and OA and arachidonic acidcontent in breast muscle and OA and LNA content in thigh muscle significantly106 n-3 polyunsaturated fatty acid enrichment in skeletalmuscle influences intramuscular fat content and adipogenesis-relatedgenes in pigs. H. F. Luo, H. K. Wei, F. R. Huang, Z. Zhou, S. W. Jiang, and J.Peng*, Huazhong Agricultural University, Wuhan, Hubei, China.The aim of the study was to investigate the effect of n-3 PUFA enrichmentin longissimus muscle on intramuscular fat (IMF) content and the expressionof adipogenesis-related genes in growing-finishing barrows. Two isoenergetic,isonitrogenous, and isolipidic diets were formulated: one was a basal dietcontaining saturated fat powder and the other contained 10% linseed. TwentyfourLandrace × NewDamLine (a cross-bred pig bred at Huazhong AgriculturalUniversity containing 25% blood of the Chinese breed “Taihu pig”) barrowsweighing 35 ± 3.7 kg were randomly assigned to 4 treatment groups with6 pigs per group. During the whole experimental period of 90 d, all groupswere first fed the basal diet and then the linseed diet for 0, 30, 60, and 90d before slaughter, respectively. Meat quality, fatty acid composition, and theexpression of genes involved in adipogenesis in longissimus muscle weremeasured and analyzed. Although drip loss, water-holding capacity, pH 45(45min after slaughter), and moisture in muscle had no significant differences(P > 0.05) among treatment groups, the IMF content increased linearly (P< 0.05) as the linseed diet feeding time prolonged. Meanwhile, n-3 PUFAcontent and the expression of peroxisome proliferator-activated receptor δ53