【作者】 赵天章；

【导师】 罗海玲；

【作者基本信息】 中国农业大学 ， 动物营养与饲料科学， 2014， 博士

【摘要】 本研究以饲料级鱼油和葵花油作为研究主体,以巴美肉羊作为研究客体,系统探讨了日粮添加不同类型油脂对舍饲羔羊瘤胃发酵、生产性能和肉品质的影响及其作用机理。选用28只平均体重为18.9kg左右的3月龄巴美肉羊公羔,随机分为四组,每组7只,分别对应饲喂4种等能等氮日粮：1)基础日粮(不添加油脂)(CONT):2)基础日粮+2.4%鱼油(FO)；3)基础日粮+2.4%葵花油(SFO)；4)基础日粮+1.8%葵花油+0.6%鱼油(FOSFO)。试验期120天,试验期内所有试验动物自由饮水。试验一：日粮添加不同类型油脂对舍饲巴美肉羊生产性能、屠宰性能和血液脂肪代谢相关指标的影响。饲养期测定巴美肉羊的生长性能和血液脂肪代谢相关指标。饲养试验结束后,试验羊全部屠宰,测定屠宰性能和血液脂肪代谢相关指标。生长性能的结果显示：日粮中添加2.4%的油脂对舍饲巴美肉羊大多数生长性能指标无影响,而鱼油组绵羊的料肉比显著低于其他三个处理组(P<0.05)。屠宰、产肉及脂肪沉积相关结果显示：日粮添加2.4%的油脂对巴美肉羊屠宰性能无影响,但显著提高了其胴体净肉率、肉骨比(P<0.05)和GR值(P<0.001)等产肉性能指标,FO组和FOSFO组还增加了其胴体腹部脂肪的沉积和背膘的加厚。血液脂肪代谢相关指标的结果显示：日粮中添加2.4%的油脂显著增加了血清中HDL-C浓度(P<0.01),而单独添加鱼油则显著降低了巴美肉羊血清胰岛素水平(P<0.01)。研究表明,日粮添加2.4%的油脂能在维持舍饲羔羊正常生长性能的前提下提高其对日粮能量的利用效率,从而在一定程度上改善其产肉性能,并促进了其胴体局部脂肪的沉积。试验二：日粮添加不同类型油脂对舍饲巴美肉羊羔羊肉品质和脂肪酸组成的影响。试验羊于饲养试验结束后全部进行屠宰,对胴体背最长肌的胸段和腰段分别进行采样,胸段背最长肌一部分于4℃保存用于现场测定pH、肉色、滴水损失及蒸煮损失,另一部分于-20℃保存用于测定肌内脂肪(IMF)和脂肪酸组成；腰段背最长肌于-20℃保存用于测定肌肉剪切力。结果显示,日粮添加2.4%的油脂有降低舍饲巴美肉羊背肌滴水损失的趋势(P<0.1),显著(P<0.05)升高了背肌pH45min值,显著(P<0.01)降低了背肌的剪切力值。对于脂肪酸组成而言,日粮添加2.4%的油脂均显著(P<0.001)提高了舍饲巴美肉羊羔羊肉脂肪酸组成中PUFA的含量及PUFA/SFA值,鱼油的添加还显著(P<0.001)增加了羔羊肉脂肪酸组成中20～22碳的n-3型PUFA的含量,从而降低了PUFA中n-6/n-3值。混合油脂的添加方式对维持舍饲羔羊背肌熟化24h后的亮度值(L*)和提高羔羊肉脂肪酸组成中PUFA/SFA值及降低PUFA中n-6/n-3值发挥了一定的协同效应(P<0.05)。研究表明,日粮添加2.4%的油脂在嫩度、持水力和脂肪酸组成等方面显著改善了舍饲巴美肉羊羔羊肉的肉品质,而选择鱼油与葵花油搭配使用可以使羔羊肉在肉色和脂肪酸组成上获得更好的综合效果。试验三：日粮添加不同类型油脂对舍饲巴美肉羊瘤胃发酵、食糜脂肪酸组成及相关氢化菌数量的影响。试验动物屠宰后采集瘤胃食糜,一部分用于瘤胃常规发酵指标及食糜脂肪酸组成分析；另一部分经四层纱布过滤后用于对瘤胃内参与CLA合成相关氢化菌数量的分析。结果显示,日粮添加2.4%油脂显著(P<0.05)升高了巴美肉羊瘤胃液pH值,显著(P<0.01)降低了总挥发性脂肪酸(TVFA)浓度,其中SFO组显著(P<0.01)降低了瘤胃液中微生物蛋白(MCP)的含量,而FO组则显著(P<0.05)降低了瘤胃液中乙酸与丙酸的比值。对于瘤胃食糜脂肪酸组成而言,日粮添加2.4%的油脂显著(P<0.001)降低了食糜短链脂肪酸(C<10)的浓度,不同类型油脂的添加对巴美肉羊瘤胃内16和18碳不饱和脂肪酸的氢化途径产生了不同的影响,同时伴随产生了一定数量的20～22碳的不饱和脂肪酸中间产物。瘤胃氢化菌qRT-PCR结果显示,日粮添加2.4%的油脂显著(P<0.05)降低了巴美肉羊瘤胃内蛋白溶解梭菌的相对数量,其中以FO组效果最明显。研究表明,三种油脂的添加对舍饲巴美肉羊瘤胃内脂肪酸代谢途径及相关氢化菌数量均有一定影响,其中瘤胃内TVA含量的积聚伴随着蛋白溶解梭菌数量的显著降低,因此推测绵羊瘤胃内蛋白溶解梭菌是主导将18碳不饱和脂肪酸氢化为硬脂酸的优势菌群。试验四：日粮添加不同类型油脂对舍饲巴美肉羊各组织中CLA合成及SCD酶mRNA表达的影响。试验动物在屠宰过程中取背最长肌、臀肌、皮下脂肪和肾周脂肪样品各50g左右用于测定CLA含量,另取50g肝脏和背最长肌样品于-80℃下保存用于测定SCD酶mRNA表达量。CLA测定结果显示,日粮添加2.4%的油脂显著升高了巴美肉羊背最长肌、臀肌、皮下脂肪和肾周脂肪中cis-9, trans-11CLA (P<0.001)、trans-10, cis-12CLA (P<0.05)和TVA(P<0.001)的相对含量,其中以单独添加鱼油效果最为明显；混合油脂的添加方式对提高舍饲巴美肉羊背肌、皮脂和肾脂中cis-9, trans-11CLA的含量存在一定协同作用(P<0.05)。对于SCD mRNA表达而言,SFO组巴美肉羊背肌中SCD酶mRNA表达量显著低于其他三个处理组(P<0.001),而FOSFO组巴美肉羊肝脏中SCD酶mRNA表达量均显著高于其他三个处理组(P<0.001)。研究表明,三种油脂的添加均显著提高了舍饲巴美肉羊胴体各组织中CLA的含量,其中单独添加葵花油或鱼油对巴美肉羊肝脏或背肌中的SCD酶mRNA表达产生了不同程度抑制作用,而鱼油与葵花油的搭配使用则明显增强了舍饲巴美肉羊肝脏中SCD酶mRNA的表达并相应地对提高巴美肉羊各组织中CLA的含量产生了协同作用。试验五：日粮添加不同类型油脂对舍饲巴美肉羊肌肉组织中肌内脂肪沉积及H-FABP基因mRNA表达的影响。试验动物在屠宰过程中分别取背最长肌和臀肌样品各200g左右,一部分于用于测定IMF含量,另一部分于-80℃下保存用于测定H-FABP基因mRNA表达。IMF测定结果显示,日粮添加2.4%的油脂对舍饲巴美肉羊背肌中IMF含量无影响(P>0.05),但显著(P<0.05)升高了臀肌中IMF的含量,且以FO组效果最为明显。对于H-FABP mRNA表达而言,FO组和SFO组对巴美肉羊臀肌中H-FABP mRNA表达量在数值上均表现出一定的降低作用,但统计分析差异不显著(P>0.05)。研究表明,日粮添加2.4%的油脂对舍饲巴美肉羊羔羊肉中IMF含量的影响因组织部位不同而有所差异,并且IMF含量升高与H-FABP mRNA表达的相关关系不明显,需后期试验进一步加以研究。综合本课题研究,日粮添加不同类型油脂,可通过提高舍饲羔羊对日粮能量的利用效率,进而在一定程度上改善其产肉性能,通过增加肌肉中PUFA、CLA和IMF等含量而显著改善了羔羊肉品质,其中混合油脂的添加有一定的协同作用,并可降低PUFA对绵羊瘤胃发酵的不利影响。更多还原

【Abstract】 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.更多还原