Effect And The Initial Mechanism Research Of Dietary Oil Sources On Fatty Acid And Intramucular Fat Contents Of Lamb

In the present study, five experiments were conducted to evaluate the effects of dietary oil sources on fatty acid composition, intramuscular fat content and its initial mechanism of feedlot lambs. Twenty-eight male Bamei lambs with initial body weight about18.9kg were individually penned and used in a complete randomized design with4treatments by7animals per group. Dietary treatments, dry matter (DM) basis, consisted of:(1) control diet (CONT) with a40:60of forage to concentrate ratio,(2) control diet supplemented with24g/kg of fish oil (FO),(3) control diet supplemented with24g/kg of sunflower oil (SFO),(4) control diet supplemented with6g/kg of fish oil+18g/kg of sunflower oil (FOSFO). All diets were formulated to be isonitrogenous, iso-energetic, and to meet all nutrient requirements for finishing lambs. Animals had free access to clean water throughout the study.Experiment1:Effect of dietary oil sources on growth performance, carcass characteristics, and lipid metabolism profile of serum in feedlot Bamei lambs. Within the120-day feeding trial, the amount of diets offered and refused was recorded daily and lambs were weighted and blooded every month for investigation of growth performance and serum lipid profile, then all animals were slaughtered for carcass characteristics evaluations at the end of the feeding trial. The results showed:compared to the CONT, FO inclusion remarkably (P<0.05) decreased the feed to gain ratio compared with other treatments, and dietary oil supplements significantly increased the meat production performance as total lean (P<0.05), muscle to bone ratio (P<0.05), and GR (P<0.001) of Bamei lambs, and animals fed diets with fish oil or oil blend showed higher abdominal fat deposit and subcutaneous fat depth compared with those in CONT and SFO (P<0.01). In addition, dietary oil supplements significantly increased HDL-C concentration in serum of Bamei lambs, and FO inclusion remarkably decreased serum insulin level compared with other treatments (P<0.01). In summary, addition of fish oil, sunflower oil, or fish oil blend with sunflower oil to diets could enhance the meat production performance and adipose deposit of partial carcass by increasing the utilization efficiency of dietary energy for feedlot Bamei lambs.Experiment2:Effect of dietary oil sources on meat quality traits and fatty acid composition of feedlot Bamei lambs. The results showed:dietary oil supplements tended to reduce (P<0.1) the drip loss, remarkably (P<0.05) increased pH45min, and significantly (P<0.01) reduced the shear force value of LD muscle in Bamei lambs. For fatty acid composition, dietary oil supplements significantly (P <0.001) increased the PUFA proportion accompanied by a remarkable increasing in PUFA/SFA of LD muscle, and lambs from FO or FOSFO had higher proportion of n-3PUFA within C20-C22and lower value of n-6/n-3of LD muscle compared with those from other treatments (P<0.001). Additionally, inclusion of fish oil blend plus sunflower oil had a significant synergistic effect on maintaining postmordem-24h L*value and increasing PUFA/SFA and decreasing n-6/n-3PUFA of LD muscle in Bamei lambs (P<0.05). In conclusion, dietary oil supplements could improve meat quality traits as tenderness, water holding capacity, and fatty acid composition of feedlot Bamei lambs, and selecting oil supplement in fish oil blend with sunflower oil way may play better performance on meat color and fatty acid profile.Experiment3:Dietary oil supplements on ruminal fermentation characteristics, fatty acid composition of ruminal digesta and populations of special bacteria responsible for hydrogenation of C18unsaturated fatty acid in the rumen of feedlot lambs. The results showed:dietary oil supplements influenced some ruminal fermentation parameters as increasing pH and reducing TVFA concentration in the rumen of Bamei lambs, and modified ruminal biohydrogenation of18-and20-carbon unsaturated fatty acids. In addition, the relative proportion of Clostridium proteoclasticum was obviously less following dietary oil supplements, especially for FO, compared with CONT. In conclusion, dietary oil inclusion altered the fermentation parameters and biohydrogenation intermediate concentrations in the rumen of feedlot Bamei lambs. Alterations in ruminal biohydrogenation to oil supplements were associated with changes in the abundance of Clostridium proteoclasticum, and Clostridium proteoclasticum was assumed to represent the predominant C18:0producers in the rumen of sheep.Experiment4:Effect of dietary oil sources on meat CLA contents and SCD mRNA expression of feedlot Bamei lambs. The results showed:(1) dietary oil supplements significantly increased the concentrations of CLA (P<0.05) and TVA (P<0.001) in meat of Bamei lambs, and FO treatment with the most obvious effect. The SCD showed lower (P<0.001) mRNA expression in LD mscle of animals fed diets containing sunflower oil compared with other treatment groups, while the SCD in liver of lambs from FOSFO had the highest mRNA expression level among all treatment groups (P<0.001). Feeding small amounts of fish oil blend plus sunflower oil exerted an additional effect on the concentration of CLA and SCD mRNA expression in feedlot Bamei lambs. These results indicated that dietary oil inclusion affected the proportion of CLA, and SFO rich in n-6PUFA inhibited the SCD mRNA expression, while FO blend with SFO could exert a synergistic effect on SCD mRNA expression in liver and simutaneously made a better performance in CLA contents in feedlot lambs.Experiment5:Effect of dietary oil sources on meat IMF contents and H-FABP mRNA expression of feedlot lambs. The results showed:dietary oil supplements significantly enhanced the IMF contents of Gluteal muscle (P<0.05), which with the most remarkable effect for FO inclusion. Feeding either fish oil or sunflower oil exerted an inhibitory effect on on H-FABP mRNA expression in Gluteal, but which without reaching the significant level (P>0.05). These results indicated that inclusion of FO or SFO in the diet of Bamei lambs could increase the IMF content of gluteal muscle, while that had no relation to H-FABP gene expression and which need further work to make clear the mechanism.In conclusion, dietary supplementation with unprotected fish oil, sunflower oil, or the mixture of fish oil blend with sunflower oil in the ratio of1:3could enhance the meat production performance, improve the carcass characteristics, and lipid profile of the meat by increasing the concentration of PUFA, CLA and IMF for feedlot Bamei lambs. Additionally, supplementing6g/kg DM of fish oil blend with18g/kg DM of sunflower oil is recommended, because it had no negative effect on the rumen fermentation and growth performance of the lambs fed high concentrate diet.