Effect And Regulation Of Linseed Oil On Meat Quality And Fat Metabolism Of Broilers

This study was to investigate the effects of linseed oil (LO) levels and duration ofsupplementation before slaughter on meat quality, fatty acid patterns and the expression ofkey genes related to lipid metabolism in liver and abdominal fat of broilers. The study wasalso conducted to determine the effects of natural vitamin E (Nat E Ac) levels and duration ofsupplementation in basal diet containing2%LO before slaughter on meat quality andoxidative stability of broiler.Experiment One was conducted to determine the effects of dietary LO levels andduration of supplementation before slaughter on growth performance, carcass traits and meatquality of broilers grown from21to42days. A total of420broilers (21d old, female) wererandomly assigned to7groups: a control group and six treatment groups according to a2×3factorial design. A control diet contained4%tallow for21d before slaughter. Low and highlevels of LO were included at2%and4%of the diet, respectively. Dietary enrichment wasprovided for3lengths of time before slaughter:7,14and21d. Results showed that comparedwith the control group, broilers fed high level of LO for a long period significantly increasedbody weight gain, shear force in both beast and thigh muscle, malonaldehyde (MDA) contentsin liver, breast and thigh muscle (P <0.05). Main effect analysis showed: compared with the2%LO group,4%LO group significantly increased MDA content in liver, breast and thighmuscle (P <0.05). Compared with broilers fed LO for7d treatment, broilers fed LO for21dsignificantly increased shear force in both beast and thigh muscle, and MDA content in thighmuscle (P <0.05). The diet supplemented LO, LO level or duration of supplementation didnot influence feed intake, the ratio of feed/gain, carcass traits, drip loss, pH and muscle color(L~*, a~*and b~*) in both beast and thigh muscle (P>0.05). There was a significant interactionbetween LO level and duration affecting the content of MDA in thigh muscle and shear forcein both beast and thigh muscle (P <0.05). These results indicated that feeding broilers withhigh level of LO for a long time before slaughter improved performance, but decreased meatquality and oxidative stability of breast and thigh muscle; different LO levels did notinfluence meat, but decreased quality oxidative stability of breast and thigh muscle; longduration of supplementation before slaughter reduced meat quality of breast and thigh muscleand oxidation stability of thigh muscle. Experiment Two was to study the effects of dietary LO level and duration ofsupplementation before slaughter on fatty acid composition in liver, breast and thigh muscleof broilers. The experimental design was the same as Experiment One. Results showed thatcompared with the control group, LO group significantly increased the contents of α-linolenicacid (ALA), docosahexaenoic acid (DHA), total polyunsaturated fatty acids (PUFA), n-3PUFA and the ratio PUFA: saturated fatty acids (SFA)(P:S) in both breast and thigh muscle,and significantly increased the contents of ALA, DHA, n-3PUFA in liver (P <0.05);decreased the ratio of n-6:n-3in liver and, as well as breast and thigh muscle (P <0.05). Maineffect analysis showed that compared with2%LO group,4%LO group increased thecontents ALA, DHA, PUFA, n-3PUFA and the ratio of P:S in both breast and thigh muscle,as well as increased the contents ALA, docosapentenoic acid and n-3PUFA in liver (P <0.05),decreased the content of SFA, the ratio of n-6:n-3in liver, and both breast and thigh muscle (P<0.05); Compared with fed LO for7d group, supplemented with LO for14d or21d groupincreased the contents of ALA, DHA, n-3PUFA, decreased SFA in both breast and thighmuscle(P <0.05); increased the contents of n-3PUFA and decreased the ratio of n-6:n-3inliver (P <0.05). Compared with fed LO for14d group, supplemented with LO for21dincreased the content of DHA and the ratio of P:S (P <0.05), decreased the ratio n-6:n-3inboth breast and thigh muscle (P <0.05); There was a significant interaction between LO leveland duration of supplementation affecting the content of ALA, DHA, n-3PUFA, PUFA, theratio of P:S and the ratio of n-6:n-3in breast and thigh muscle and SFA, PUFA, n-3PUFA andthe ratio of n-6:n-3in liver (P <0.05). These results indicate that broilers fed LO diet, higherLO level, medium or long durations of supplementation before slaughter was an efficientenrichment procedure of n-3PUFA, a balanced ratio of P:S and n-6:n-3in breast and thighmuscle.Experiment Three was to investigate the effects of dietary LO level and duration ofsupplementation before slaughter on fat metabolism and mRNA abundance of genes thatinvolve the metabolism of fat in liver and abdominal fat. The experimental design was thesame as Experiment One. Compared with the control group, broilers fed high level of LO fora long period significantly increased the contents of high density lipoprotein cholesterol(HDL-C) in plasma, lipoprotein lipase (LPL) and peroxisome proliferator-activated receptorsα (PPAR-α) mRNA abundance in liver (P <0.05), decreased percentage of abdominal fat, thecontent of total cholesterol (TC), low density lipoprotein cholesterol (LDL-C) in plasma andfatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), liver fatty acid binding protein(L-FAB) mRNA abundance in liver PPAR-γ mRNA abundance in abdominal fat (P <0.05).Main effect analysis showed that compared with2%LO group,4%LO group increased the contents of intramuscular fat content in both beast and thigh muscle, as well as LPL mRNAabundance in liver (P <0.05), decreased ACC mRNA abundance in liver (P <0.05).Compared with group fed LO for7d, supplemented with LO for14d or21d decreasedpercentage of abdominal fat, the content of TC and LDL-C in plasma, ACC mRNAabundance in liver and LPL mRNA abundance in abdominal fat (P <0.05); compared withfed LO for7d or14d group, supplemented with LO for21d increased the contents ofHDL-C in plasma, intramuscular fat content in both beast and thigh muscle, as well as LPLmRNA abundance in liver (P <0.05). Compared with group fed LO for7d, supplementedwith LO for21d decreased the content of triglyceride (TG) in plasma (P <0.05). Theseresults indicated that broilers fed LO diet, medium or long duration of supplementation beforeslaughter decreased percentage of abdominal fat by altering blood lipids content andincreasing lipolysis and decreasing lipogenesis genes mRNA abundance in liver andabdominal fat.Experiment Four was to investigate the effects of dietary Nat E Ac levels and duration ofsupplementation before slaughter on growth performance, carcass traits, meat quality,α-tocopherol content and oxidation stability of serum, breast and thigh muscle refrigerated at4℃of broilers. Cobb broilers (n=315,21d old, female) were randomly allotted to7treatments (1control group and6treatment groups) with5replicates of9broilers each.Control group was fed basal diet (Nat E Ac:30IU/kg); experiment groups were a2×3factorial experiment with2dietary Nat E Ac levels (Nat E Ac:60and120mg/kg) and3durations (7,14and21d) before slaughter at42d. Results showed that compared withcontrol group, Nat E Ac group markedly increased α-tocopherol content in plasma (P <0.05),decreased drip loss in breast muscle, MDA content in plasma and in breast musclerefrigerated at4℃for0,2,4,6,8d and in thigh muscle refrigerated at4℃for6d (P <0.05).Main effect analysis showed that compared with60mg/kg Nat E Ac group,120mg/kg Nat EAc group markedly increased percentage of breast muscle, pH24hin breast muscle, thecontents of fat and glutathione peroxidase in liver, α-tocopherol content in plasma, liver, breastand thigh muscle (P <0.05), deceased△pH in breast muscle, drip loss in breast and thighmuscle, and the content of MDA in breast and thigh muscle refrigerated at4℃for0,2,4,6,8d (P <0.05). Compared with fed LO for7d group, supplemented with LO for21d groupincreased percentage of breast and thigh muscle, intramuscular fat in both breast and thighmuscle, fat content in liver, pH24hin breast muscle, α-tocopherol content in plasma, liver, breastand thigh muscle (P <0.05), decreased drip loss in breast and thigh muscle,△pH in breastmuscle MDA content in plasma and in breast and thigh muscle refrigerated at4℃for0,2,4,6,8d (P <0.05). Compared with fed LO for7d group, supplemented with LO for14d group decreased MDA content in plasma and in breast muscle refrigerated at4℃for0,6,8d andthigh muscle refrigerated at4℃for0,4,6d (P <0.05). The basal diet (2%linseed oil)combination of60mg/kg or120mg/kg Nat E Ac during the14d or21d prior to slaughter.These results indicated that broilers supplemented with Nat E Ac in basal diet concluding2%LO, high level of Nat E Ac, medium or long duration of supplementation before slaughterimproved meat quality and enhanced oxidative stability during refrigerated storage throughincreasing α-tocopherol retention in liver, breast and thigh muscle.The study indicated that feeding broilers with LO for long duration of supplementationdecreased meat quality. Supplementation with LO in basal diet, high LO level and longduration of supplementation increased lipid oxidation of chicken. The addition of Nat E Ac inbasal diet, high level Nat E Ac, and medium or long duration of supplementation improvedmeat quality and enhanced oxidative stability of broiler meat. Broilers fed LO diet, higher LOlevel, medium or long duration of supplementation before slaughter was recommended as anefficient enrichment procedure of n-3PUFA, a balanced P:S and n-6:n-3ratio in breast andthigh muscle. The addition of LO in basal diet, and medium or long duration ofsupplementation reduced abdominal fat by changing blood lipids content, increasing lipolysisor decreasing lipogenesis genes mRNA abundance in liver and abdominal fat.