Bell J A, Griinari J M, Kennelly J J
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6G 2P5.
J Dairy Sci. 2006 Feb;89(2):733-48. doi: 10.3168/jds.S0022-0302(06)72135-X.
Conjugated linoleic acid (CLA) refers to a mixture of conjugated octadecadienoic acids of predominantly ruminant origin. The main isomer in bovine milk fat is the cis-9, trans-11 CLA. Interest in CLA increased after the discovery of its health-promoting properties, including potent anticarcinogenic activity. Two experiments were conducted to evaluate dietary strategies aimed at increasing the concentration of CLA in bovine milk fat. Both experiments were organized as a randomized complete block design with a repeated measures treatment structure. In Experiment 1, 28 Holstein cows received either a control diet or one of 3 treatments for a period of 2 wk. The control diet consisted of 60% forage (barley silage, alfalfa silage, and alfalfa hay) and 40% concentrate on a dry matter (DM) basis, fed as a total mixed ration (TMR). The concentrate was partially replaced in the treatment groups with 24 ppm of monensin (MON), 6% of DM safflower oil (SAFF), or 6% of DM safflower oil plus 24 ppm of monensin (SAFF/M). Average cis-9, trans-11 CLA levels in milk fat after 2 wk of feeding were 0.45, 0.52, 3.36, and 5.15% of total fatty acids for control, MON, SAFF, and SAFF/M, respectively. In Experiment 2, 62 Holstein cows received either a control diet or one of 5 treatment diets for a period of 9 wk. The control diet consisted of 60% forage (barley silage, alfalfa silage, and alfalfa hay) and 40% concentrate on a DM basis, fed as a TMR. The concentrate was partially replaced in the treatment groups with 6% of DM safflower oil (SAFF), 6% of DM safflower oil plus 150 IU of vitamin E/kg of DM (SAFF/E), 6% of DM safflower oil plus 24 ppm of monensin (SAFF/M), 6% of DM safflower oil plus 24 ppm of monensin plus 150 IU of vitamin E/kg of DM (SAFF/ME), or 6% of DM flaxseed oil plus 150 IU of vitamin E/kg of DM (FLAX/E). Average cis-9, trans-11 CLA levels during the treatment period were 0.68, 4.12, 3.48, 4.55, 4.75, and 2.80% of total fatty acids for control, SAFF, SAFF/E, SAFF/M, SAFF/ME, and FLAX/E, respectively. The combination of safflower oil with monensin was particularly effective at increasing milk fat CLA. The addition of vitamin E to the diet partially prevented the depression in milk fat associated with oilseed feeding, but had no significant effect on the concentration of CLA in milk.
共轭亚油酸（CLA）是指主要来源于反刍动物的共轭十八碳二烯酸的混合物。牛乳脂肪中的主要异构体是顺-9，反-11 CLA。在发现CLA具有促进健康的特性（包括强大的抗癌活性）后，人们对其兴趣增加。进行了两项实验，以评估旨在提高牛乳脂肪中CLA浓度的日粮策略。两项实验均采用随机完全区组设计，具有重复测量处理结构。在实验1中，28头荷斯坦奶牛接受对照日粮或3种处理日粮之一，为期2周。对照日粮按干物质（DM）计由60%的粗饲料（大麦青贮、苜蓿青贮和苜蓿干草）和40%的精饲料组成，以全混合日粮（TMR）形式饲喂。在处理组中，精饲料部分被24 ppm的莫能菌素（MON）、6% DM的红花油（SAFF）或6% DM的红花油加24 ppm的莫能菌素（SAFF/M）替代。饲喂2周后，乳脂肪中顺-9，反-11 CLA的平均水平分别为对照、MON、SAFF和SAFF/M组总脂肪酸的0.45%、0.52%、3.36%和5.15%。在实验2中，62头荷斯坦奶牛接受对照日粮或5种处理日粮之一，为期9周。对照日粮按DM计由60%的粗饲料（大麦青贮、苜蓿青贮和苜蓿干草）和40%的精饲料组成，以TMR形式饲喂。在处理组中，精饲料部分被6% DM的红花油（SAFF）、6% DM的红花油加150 IU维生素E/kg DM（SAFF/E）、6% DM的红花油加24 ppm的莫能菌素（SAFF/M）、6% DM的红花油加24 ppm的莫能菌素加150 IU维生素E/kg DM（SAFF/ME）或6% DM的亚麻籽油加150 IU维生素E/kg DM（FLAX/E）替代。处理期间，对照、SAFF、SAFF/E、SAFF/M、SAFF/ME和FLAX/E组乳脂肪中顺-9，反-11 CLA的平均水平分别为总脂肪酸的0.68%、4.12%、3.48%、4.55%、4.75%和2.80%。红花油与莫能菌素的组合在提高乳脂肪CLA方面特别有效。在日粮中添加维生素E可部分防止与饲喂油籽相关的乳脂肪降低，但对乳中CLA浓度无显著影响。
