Song S Z, Wu J P, Zhao S G, Casper D P, He B, Liu T, Lang X, Gong X Y, Liu L S
J Anim Sci. 2017 Sep;95(9):3940-3948. doi: 10.2527/jas2016.1235.
Sheep production systems in northwest China depend mostly on natural grasslands. Seasonal growth and maturity fluctuations can cause periodical restrictions in food quality and quantity. These fluctuations, in turn, result in variability in fat deposition and fatty acid profiles in different fat depots. Consequently, the study objective was to compare fat deposition, intramuscular fat (IMF) percentage and fatty acid profiles of the longissimus dorsi (LD), kidney fat (KF), tail fat (TF), and subcutaneous fat (SF) in lambs under ME restrictions similar to seasonal changes observed in the natural grasslands of northwest China. Nineteen male Dorper × Small Tailed Han lambs were assigned to 2 treatments, a control (CON) fed at 1.0 MJ / W × d and restricted (RES) by restricting ME sequentially every 30 d (0.56 MJ / W × d, 0.84 / W × d, 1.0 MJ / W × d, 0.84 MJ / W × d, 0.56 MJ / W × d, 0.28 MJ / W × d). All lambs were harvested at the end of the 180 d experimental period. Compared to CON fed lambs, restricting ME resulted in lesser IMF, fat deposition indexes ( < 0.05) except testicular and heart fat and greater ( < 0.05) SFA in LD, KF, and TF depots. The RES fed lambs had greater ( < 0.05) -3 PUFA, eicosatrienoic acid (C20:3n3), eicosapentaenoic acid (C20:5n3, EPA), and trans-linolelaidic acid (C18:2n6t) in LD muscle. The conjugated linoleic acids (CLA) content was greater in the SF depots of the CON fed lambs compared to the RES fed lambs. Fatty acid ratios (unsaturated fatty acid; USFA:SFA, MUFA:SFA, PUFA:SFA), and percentage USFA in RES fed lambs were lesser in muscle and adipose tissue compared to CON fed lambs ( < 0.05), except SF depots. In RES fed lambs, EFA were less ( < 0.05) in LD and KF depots and the ratios of functional fatty acids were lesser in LD and some adipose tissues ( < 0.05), including lesser n-6:n-3 in KF and SF ( < 0.05) depots, lesser USFA, SFA, MUFA, SFA in LD, KF, and TF ( < 0.05) depots, and lesser PUFA and SFA in LD and TF ( < 0.05) depots. Results from this research demonstrate that sequential energy restriction, as might be experience during seasonal forage quality and quantity changes in natural grasslands, result in lesser intramuscular fat with associated lesser quality, as well as, changes in fatty acid composition in different fat depots, which has implications for both meat quality and animal physiological functions.
中国西北的绵羊生产系统主要依赖天然草原。季节性的生长和成熟波动会导致食物质量和数量出现周期性限制。这些波动进而导致不同脂肪库中脂肪沉积和脂肪酸组成的变化。因此，本研究的目的是比较在类似于中国西北天然草原季节性变化的代谢能限制条件下，羔羊背最长肌（LD）、肾周脂肪（KF）、尾脂（TF）和皮下脂肪（SF）的脂肪沉积、肌内脂肪（IMF）百分比及脂肪酸组成。19只雄性杜泊×小尾寒羊羔羊被分为2组处理，一组为对照组（CON），按1.0 MJ / W×d饲喂，另一组为限制组（RES），每30天依次限制代谢能（0.56 MJ / W×d、0.84 / W×d、1.0 MJ / W×d、0.84 MJ / W×d、0.56 MJ / W×d、0.28 MJ / W×d）。所有羔羊在180天试验期结束时屠宰。与CON组饲喂的羔羊相比，限制代谢能导致IMF、脂肪沉积指数降低（睾丸和心脏脂肪除外，P<0.05），且LD、KF和TF脂肪库中的饱和脂肪酸（SFA）含量增加（P<0.05）。RES组饲喂的羔羊LD肌中-3多不饱和脂肪酸（PUFA）、二十碳三烯酸（C20:3n3）、二十碳五烯酸（C20:5n3，EPA）和反式亚油酸（C18:2n6t）含量更高（P<0.05）。CON组饲喂的羔羊SF脂肪库中共轭亚油酸（CLA）含量高于RES组饲喂的羔羊。与CON组饲喂的羔羊相比，RES组饲喂的羔羊肌肉和脂肪组织中脂肪酸比率（不饱和脂肪酸；USFA:SFA、MUFA:SFA、PUFA:SFA）及USFA百分比更低（SF脂肪库除外，P<0.05）。在RES组饲喂的羔羊中，LD和KF脂肪库中的必需脂肪酸（EFA）含量更低（P<0.05），LD和一些脂肪组织中功能性脂肪酸的比率更低（P<0.05），包括KF和SF脂肪库中n-6:n-3更低（P<0.05），LD、KF和TF脂肪库中USFA、SFA、MUFA、SFA更低（P<0.05），LD和TF脂肪库中PUFA和SFA更低（P<0.05）。本研究结果表明，如天然草原季节性草料质量和数量变化时可能经历的那样，连续能量限制会导致肌内脂肪减少且质量下降，以及不同脂肪库中脂肪酸组成的变化，这对肉品质和动物生理功能均有影响。
