Effect Of Dietary ω6/ω3 On Fatty Acid Composition And Meat Quality In Chickens

Four experiments were conducted to study the effects of dietaryω6/ω3 on growth performance, carcass traits, fat deposition, meat quality, fatty acids composition and expression of key genes related to meat quality or lipid metabolism in chicken. Method for isolation and culture of chicken hepatocytes was established, by which effect of fatty acids on proliferation of hepatocytes was examined.Trail 1 was carried out to assess the effects of dietaryω6/ω3 on growth performance, carcass traits, fat deposition, meat quality and fatty acids composition of AA broiler. The results showed that birds fed 10: 1 diet incorporated significantly higher body weight (BW) and average daily feed intake (ADFI) than fed the other birds. Percentage of dressing (PD), eviscerated carcass (PEC) decreased significantly as dietaryω6/ω3 was reduced; percentage of abdominal fat (PAF), subcutaneous fat (SBF) and intermuscular fat (IF) were higher in birds fed lower ratio diets. Drip loss (DL) in both breast and thigh muscle increased significantly in birds fedω6/ω3 ratio from 18 to 2.6. Except b* value in breast muscle decreased as birds fed dietary ratio from 5 to 2.6, the tendency for breast and thigh muscle were almost similar; a* values progressively increased as the diets contained increasingω3 content, changes in b* were also significant but the pattern was almost the reverse for changes in a*. Decreasing the dietaryω6/ω3 clearly increased the contents of ALA, EPA and DPA, but not for DHA. Liver had lower ALA, higher C20: 3, EPA and DHA than breast muscle. The results clearly demonstrated that decreasing the dietaryω6/ω3 by supplementing 3 % oil, improves meat quality of AA broiler, and increases deposition of desirableω3 andω6 long chain PUFA in the edible tissues, thereby achieving nutritionally enriched meat.Trail 2 was conducted to study the effects of dietaryω6/ω3 on fat deposition, meat quality and fatty acids composition of Beijing-you chicken. The results showed that birds fed 5: 1 diet gained significantly higher BW and feed intake to gain ratio (F/G) than fed the other diets. For both breast and thigh muscle, birds fed the 10:1ω6/ω3 diet incorporated significantly (P < 0.05) higher intramuscular fat and IF than did birds fed the other diets; all carcass traits increased significantly (P < 0.001) from 6 to 22 wk. Shear force (SF), L* or b* value of meat color and DL in breast muscle decreased, while inosine-5'-monophosphate (IMP) and a* value increase, as the diets contained increasingω3 content, up to the 5:1ω6/ω3 (P < 0.01). Regardless of diet, a* value of meat color and pH at 1h postmortem declined (P < 0.001) between 6 and 22 wk. Chickens fed for 13 wk had the highest (P < 0.001) SF and IMP content, and lowest DL in breast muscle. Decreasing the dietaryω6/ω3 significantly increased (P < 0.001) the contents of ALA, EPA and DPA, but not DHA in both breast muscle and liver. Both LA and ALA were at lower levels in liver tissue lipid than in muscle. The most obvious difference in the effect of time on fatty acid composition between muscle and liver was that the percentage of ALA, DPA, and totalω3 PUFA were highest at 13 wk, but the percentage of mostω3 PUFA (EPA, DPA, DHA, and totalω3 PUFA) and allω6 PUFA decreased (P < 0.001) with time. This study clearly shows that decreasing the dietaryω6/ω3, without change in total dietary lipid, increases the efficiency of ALA to its long chain derivatives, with the exception of DHA. The pronounced effects of the diets on IMF could indicate that the 10:1ω6/ω3 ratio was optimal for de novo lipogenesis. The highest IMP content and lowestω6/ω3 in breast muscle at 13 wk provided proof for marketing the Beijing-you chicken.Trail 3 investigated effects of dietaryω6/ω3 on gene expression related to meat quality and lipid metabolism in different breeds and age by Q-PCR. Results showed that the expression ofΔ6 FAD in abdominal fat was highest in Beijng-you chickens of 6 wk fed dietary ratio of 10 and 2.6. A-FABP expression increased significantly (P < 0.001) from 6 to 22 wk. Decreasing the dietaryω6/ω3 significantly increased (P < 0.001) the expression of LPL in abdominal fat, and the highest expression level for LPL occurred at 6 wk for Beijing-you chicken. The expression of CAPN1 progressively increased as the diets contained increasingω3 content, the changes in ALDH1A1 were also significant but the pattern was almost the reverse of changes in CAPN1. Apo-AⅠgene expression in Beijing-you chicken was lower than that in AA broiler, and fed 10: 1 diet was higher than other diets. In conclusion, the expression ofΔ6 FAD and LPL was higher in younger birds, LPL, ALDH1A1, Apo-AⅠand CAPN1 expression was significantly influenced by varying dietaryω6/ω3, there were significantly different of Apo-AⅠand H-FABP expression between two breeds.Trail 4 examined effect of LA, ALA and different LA/ALA ratio on proliferation of chicken hepatocytes. The results showed that high purity and viability of hepatocytes could be obtained by two steps in situ circulatory perfusion method with little 0.05 % collagenaseП. MTT results showed that ratio of 10 for LA/ALA promoted proliferation of hepatocytes after culture for 72 h.In conclusion, this study from in vivo suggests that, the efficiency of the chicken to convert ALA to EPA and DPA can be improved by feeding a diet of lowerω6/ω3 ratio with a relatively low amount of total added fat. The following molecular test demonstrated this result further, and found the best ability of conversion to long chain fatty acids occurred in younger birds. Furthermore, the results from in vitro that the 10: 1 ratio of LA/ALA can promote the proliferation of hepatocytes, along with the highest IMF content and Apo-AⅠexpression in Beijing-you chicken fed 10: 1 diet in vivo, may be closely associated with the influence of this ratio on lipid metabolism, stability and growth of organism.