Feeding Unprotected CLA Methyl Esters Compared to Sunflower Seeds Increased Milk CLA Level but Inhibited Milk Fat Synthesis in Cows
Feeding Unprotected CLA Methyl Esters Compared to Sunflower Seeds Increased Milk CLA Level but Inhibited Milk Fat Synthesis in Cows
复制标题
DOI：
10.5713/ajas.2011.11146
复制
发表时间：
2012-01-01
期刊：
影响因子：
--
通讯作者：
Bee, G.
中科院分区：
文献类型：
--
作者：
Dohme-Meier, F.;Bee, G.
本试验比较了等量的18：2n-6和未保护的18：2c9t11和18：2t10c12混合饲喂对仔猪采食量、乳成分以及血浆和乳脂肪酸谱的影响。根据产奶量和乳脂率将15头奶牛随机分配到3个处理中的1个处理(n=5)。每头奶牛在基础日粮上度过12天的调整期(AP)。AP奶牛在18d的试验期(EP)内接受了3种补充剂中的1种。这些补充剂包括1公斤葵花籽粉(S)、0.5公斤共轭亚油酸(CLA)油(C)或0.75公斤葵花籽粉和CLA油的混合物(2：1；SC)。所有3种补充剂都含有等量的18：2共轭亚油酸(Sigma 18：2c9t11+18：2t10c12，1：1)或18：2c9c12。在AP的最后2d和EP的最后4d，每天记录采食量和产奶量，并在每次挤奶时采集乳样。分别于AP治疗后第11天、EP治疗后第15、18天采集颈静脉血。从AP到EP的所有处理均增加了18：2摄入量。无论添加多少共轭亚油酸，处理C和处理SC的乳脂率分别降低了2.35和2.10个单位，而S组下降幅度较小，为0.99个单位。因此，C和SC奶牛每天排出的乳脂量低于S奶牛。血浆和乳汁中反式18：1的浓度从AP到EP逐渐升高，并随着日粮中CLA供应量的增加而增加。当血浆中18：2c9t11和18：2t10c12以及牛奶中18：2t10c12的浓度与日粮平行时，乳中18：2c9t11的水平在C组和CS组相似，但在S组仍然较低。虽然CLA在处理C的饲料浓度最高，但葵花籽部分取代CLA对乳脂合成的抑制作用相似。在两种共轭亚油酸处理中，牛奶中18：2c9t11的水平相当，这意味着随着供应量的增加，该异构体受到更大的生物氢化作用。无保护的18：2t10c12逃脱了足够数量的生物氢化以影响乳脂合成的事实表明，在奶牛的新陈代谢状态需要或希望减少乳脂产生的情况下，有机会制定喂养策略。
An experiment was conducted to compare the effect of the same amount of 18:2 offered either as 18:2n-6 or as a mixture of unprotected 18:2c9t11 and 18:2t10c12 on feed intake, milk components as well as plasma and milk fatty acid profile. Fifteen cows were blocked by milk yield and milk fat percentage and within block assigned randomly to 1 of 3 treatments (n = 5). Each cow passed a 12-d adjustment period (AP) on a basal diet. After the AP cows received 1 of 3 supplements during an 18-d experimental period (EP). The supplements contained either 1.0 kg ground sunflower seeds (S), 0.5 kg conjugated linoleic acid (CLA)-oil (C) or 0.75 kg of a mixture of ground sunflower seeds and CLA-oil (2:1; SC). All 3 supplements contained the same amount of 18:2 either as CLA (Sigma 18:2c9t11+18:2t10c12, 1:1) or as 18:2c9c12. During the last 2 d of AP and the last 4 d of EP feed intake and milk yield were recorded daily and milk samples were collected at each milking. Blood samples were collected from the jugular vein on d 11 of AP and d 15 and 18 of EP. The 18:2 intake increased in all treatments from AP to EP. Regardless of the amount of supplemented CLA, the milk fat percentage decreased by 2.35 and 2.10%-units in treatment C and SC, respectively, whereas in the treatment S the decrease was with 0.99%-unit less pronounced. Thus, C and SC cows excreted daily a lower amount of milk fat than S cows. The concentration of trans 18:1 in the plasma and the milk increased from AP to EP and increased with increasing dietary CLA supply. While the concentration of 18:2c9t11 and 18:2t10c12 in the plasma and that of 18:2t10c12 in the milk paralleled dietary supply, the level of 18:2c9t11 in the milk was similar in C and CS but still lower in S. Although the dietary concentration of CLA was highest in treatment C, the partial replacement of CLA by sunflower seeds had a similar inhibitory effect on milk fat synthesis. Comparable 18:2c9t11 levels in the milk in both CLA treatments implies that this isomer is subjected to greater biohydrogenation with increasing supply than 18:2t10c12. The fact that unprotected 18:2t10c12 escaped biohydrogenation in sufficient amounts to affect milk fat synthesis reveals opportunities to develop feeding strategies where reduced milk fat production is desirable or required by the metabolic state of the cow.