【摘要】 本研究旨在通过同时灌注葡萄糖和胰岛素,研究胰岛素对奶山羊乳脂合成的影响并探讨其机理。选取4只泌乳中后期文登奶山羊安装颈动脉、颈静脉和乳静脉临时插管,采用2×2交叉试验设计,分为2个处理,即对照和葡萄糖和胰岛素灌注处理。试验共分2期,每期10 d,前5 d为基准物质测试期,后5 d为灌注期,2期试验间隔5 d。接受葡萄糖和胰岛素灌注的试验羊由颈静脉插管注射葡萄糖和胰岛素,从颈动脉和乳腺静脉插管采集血样。胰岛素、葡萄糖持续注射(24 h/d),胰岛素注射速率为1μg/h·kg BW,葡萄糖(25%w/v)的注射速率以将血糖浓度控制在基础浓度的±20%来确定。试验期间试验羊精料分12等份,自动投料机每2 h投喂1次,试验羊自由饮水。结果表明,葡萄糖和胰岛素同时灌注显著提高了血浆胰岛素浓度(P<0.05),血糖浓度与对照组差异不显著(P>0.05),达到了预期处理效果。葡萄糖和胰岛素同时灌注显著降低了奶山羊的乳脂率和乳脂产量(P<0.05),而对产奶量、乳蛋白率和乳糖含量的影响不显著(P>0.05)。葡萄糖和胰岛素同时灌注显著降低了动脉血浆甘油三酯(triglycerides,TG)、乙酸和游离脂肪酸(nonesterified fatty acids,NEFA)的浓度(P<0.05);显著降低了乳腺组织对动脉NEFA的吸收率和NEFA的吸收速度(P<0.05),但显著升高了动脉对乙酸的吸收率(P<0.05);显著升高了乳脂脂肪酸中C12:0、C14:O和C16脂肪酸的含量(P<0.05)和降低了C18:0(P<0.05)、trans-C18:1(P>0.1)脂肪酸的含量,trans-10,cis-12CLA的含量无显著变化(P>0.1)。葡萄糖和胰岛素同时灌注未影响乳脂中中链脂肪酸(C10-16)和长链脂肪酸(≥C18)的比例(P>0.05),但降低了乳脂中短链脂肪酸(C4-8)比例(P<0.05)。本研究结果表明,胰岛素可以引起奶山羊乳脂率的降低,其主要的途径可能是降低乳腺对动脉血液NEFA和TG的吸收。更多还原

【Abstract】 This experiment was conducted to study the influence of hyperinsulinemic and euglycemic simultaneous infusion on milk fat synthesis in lactating goats. In the experiment, four mid-late lactation Wendeng goats with temporary carotid, jugular vein, and mammary vein catheters were assigned to a 2×2 cross-over experiment of 2 treatments including control and hyperinsulinemic and euglycemic simultaneous infusion treatment. The experiment consisted of 2 periods with each of 10 d, and there was an interval of 5 d between the 2 periods. The first five days in each period was for the baseline measurements, while the second five days for the hyperinsulinemic and euglycemic simultaneous infusion. During the experiment, insulin and glucose were injected continuously (24 h/d). The rate of insulin injection through jugular vein catheter was 1 μg/h • kg BW, while that of glucose injection was adjusted on the basis that blood glucose (25% w/v) concentration was kept within ± 20% of the base level. Daily mixed concentrate was equally divided into 12 parts and delivered by the automatic feeder every two hours, and water was free to drink during the experiment. The study results showed that the hyperinsulinemic and euglycemic treatment significantly increased the plasma insulin concentration, and there was no significant difference in the blood glucose concentration from the control group, realizing the expected treatment effects. Both milk fat content and yield significantly decreased in infusion goats (P<0.05), and there was no significant effect on other milk components (P> 0. 05). Hyperinsulinemic and euglycemic simultaneous infusion treatment significantly decreased the TG, acetic acid and NEFA concentration (P<0. 05) and the rate and speed of the mammary tissue’s absorption of NEFA, while significantly increased the speed of its absorption of acetic acid. Milk fatty acid compositions have been modified by infusion treatment. Contents of C12:0 ,C14 : 0 and C16 in milk fat increased(P<0. 05), while that of C18:0 and trans-C18:1 decreased, but there was no effect on trans-10,cis-12CLA. Contents of total medium chain fatty acids (C10-16) and total long chain fatty acids (≥C18) in milk fat was not affected by the infusion treatment, but that of short chain fatty acids (C4-8) showed a significant decrease (P<0. 05). As shown in the results of this study, insulin may lead to the decrease in milk fat by decreasing the availability of absorbed fatty acid for milk fat synthesis in mid-late lactating goats.更多还原