| Lipid metabolism is very important for the improvement of meat quality and flavors. The aim of the present study was to examine the effects of fatty acid on meat quality of chickens. Firstly, gene-chips for chicken transcripts were used to study differences in gene expression related to lipid metabolism from different muscle samples, which were shown to have large differences in fat traits. Differentially expressed genes were filtered further, and were viewed as being possible candidate genes for meat quality. Secondly, an additional experiment studied the effect of dietary supplementation with vitamin E on meat quality, lipid anti-oxidation and fatty acid composition of muscle lipids in chickens. On the basis of the results of the first study, expression of genes related to lipid transport, oxidation and regulation were studied for their sensitivity to dietary supplementation with vitamin E.Trial 1 The expression of genes related to fat trait were studied initially by hybridization to chicken gene-chips (Affymetrix). Paired designs were used to compare transcripts in breast muscle of Beijing-you (BJY) and AA broilers, and thigh muscle to breast muscle in BJY chickens. Differential expressing genes of both comparisons were filtered (two-fold or greater hybridization signals) to expose significant genes involved in regulating lipid metabolism. The research showed:1. Carcass traits were significantly different between AA broilers and BJY chickens of similar boby weight. The percentage eviscerated carcass, muscle yield, percentage of abdominal fat, and subcutaneous fat of AA broilers were significantly higher (P < 0.05) than those of BJY chickens. The IMF content of breast muscle from AA broilers was significantly lower (P < 0.05) than that in BJY chickens. In BJY chickens, the IMF content of breast muscle was significantly lower (P < 0.05) than that of thigh muscle.2. Drip loss and a* of breast muscle from BJY chickens were notably lower (P < 0.05) than of breast muscle from AA broilers, but L*, b* values were the opposite. The pH of thigh muscle in BJY chickens was significantly higher (P < 0.05) than those of breast muscle in both BJY and AA chickens.3. A total of 3,148 genes were differentially expressed in breast muscle in BJY chickens when compared to AA broilers, including 3,017 of known function and 133 of unknown function. When thigh and breast muscle of BJY chickens were compared, 1,939 genes were identified, including 1,870 of known function and 69 of unknown function.4. Most of the differentially expressed genes were concerned with three bioprocesses by GO analysis: cellular physiological and metabolic processes; structural composition of cell and sub-cellular membranes; regulation of lipid binding and catalyzing and transporting activities.5. A total of 35 genes related to lipid metabolism (including H-FABP, PPAR, PLA2, LPL, FAS, ApoA1 and ApoB) were obtained in both comparisons by Functional Annotation Clustering. These genes offered important gene clusters of fatty acid metabolism and meat quality.6. The KEGG pathways were analyzed, and the key genes were obtained from significant pathways: aldehyde dehydrogenase 1 family, member a1 (ALDH1A1), hydroxyacyl - coenzyme a dehydrogenaseβ/α(HADHB/A), acetyl-Coenzyme A acyltransferase 2 (ACAA2). Furthermore, HADHB and ACAA2 genes are at critical regulatory points in the pathways.7. ApoA1, HADHB and ACAA2 genes, were established on the basis of known function and previous research, to be key genes related to regulating lipid metabolism.Trial 2 The effects of dietary supplementation with vitamin E on carcass and meat quality, oxidative stability, fatty acid composition of muscle were examined in BJY chickens, along with the expression of genes (selected on the basis of the first Trial) as being related to lipid metabolism. The maize-soybean feed for each treatment was supplemented with vitamin E (0, 10, 50, 100, 150, or 200 mg/kg feed). The 1 d female BJY chicks (540 birds) and were distributed across 6 treatments, containing 3 replicates (each of 30 birds). The birds were raised under the same conditions to 8 or 17 wk, when 30 birds from each treatment were slaughtered to examine the effect of dietary vitamin E supplementation on evaluated traits. This research showed:1. Supplemental vitamin E in the diet significantly increased (P < 0.05) the content ofα-tocopherol in breast and thigh muscles.2. Dietary vitamin E increased intramuscular fat contents of breast and thigh muscles and decreased percentage of abdominal fat at 17 wk (P < 0.05).3. Dietary vitamin E significantly (P < 0.05) decreased drip loss of muscle and increased the a* value. Thiobarbituric acid reactive substance (TBARS) values decreased (P < 0.05) with increasing dietary vitamin E, and the addition of 100 mg/kg or more had a beneficial effect (P < 0.05) on the oxidative stability as indicated by TBARS values during storage up to 7 d.4. Supplementation with vitamin E significantly decreased the proportions in muscle lipids of C14:0, C16:0 and C18:0 while increasing those of C18:2, C18:3 and C22:6 at 17 wk (P < 0.05).5. Vitamin E supplementation at 200 mg/kg significantly (P < 0.05) inhibited expression of the phospholipase A2 (PLA2), while enhancing that of the peroxisome proliterator-activated receptor beta (PPAP-β) and heart fatty acid binding protein (H-FABP) genes in breast muscle at 17 wk. The results indicate that dietary supplementation with vitamin E increased lipid stability in muscle and improved meat quality and fatty acid composition, probably by its influence on the expression of genes related to lipid metabolism.
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