Kalscheur K F, Teter B B, Piperova L S, Erdman R A
University of Maryland, College Park 20742, USA.
J Dairy Sci. 1997 Sep;80(9):2115-26. doi: 10.3168/jds.S0022-0302(97)76157-5.
The objective of the study was to determine the effects of dietary fat source on duodenal flow, apparent absorption, and milk fat incorporation of trans-C18:1 fatty acids. Four ruminally and duodenally cannulated multiparous Holsteins cows in mid to late lactation were fed a basal diet containing 36% corn silage, 24% alfalfa haylage, and 40% concentrate (dry matter basis). Diets contained 0% supplemental fat (control diet), 3.7% high oleic sunflower oil, 3.7% high linoleic sunflower oil, or 3.7% partially hydrogenated vegetable shortening; treatments were administered in a 4 x 4 Latin square design with 3-wk experimental periods. The flow of trans-C18:1 to the duodenum was higher for cows fed diets supplemented with fat than for cows fed the control diet (283 vs. 64 g/d). Incomplete biohydrogenation accounted for the increased flow of trans-C18:1 to the duodenum in cows fed diets containing high oleic and high linoleic sunflower oil. Increased flow of trans-C18:1 in cows fed the diet containing partially hydrogenated vegetable shortening most likely originated from the trans-C18:1 in the diet. Milk fat percentages were 3.48, 3.07, 3.18, and 3.38% for cows fed the control diet and diets containing high oleic sunflower oil, high linoleic sunflower oil, and vegetable shortening, respectively. Milk trans-C18:1 increased from 2.9 to 11.2% of the total fatty acids for cows fed the control diet and the diets supplemented with fat, respectively. Milk trans-C18:1 were equal across all diets supplemented with fat. Ruminal and total tract digestion of organic matter, neutral detergent fiber, and N did not change with fat supplementation. Results showed that trans-C18:1 is increased in the milk of cows with reduced milk fat; however, excessive amounts of trans-C18:1 in milk do not necessarily correspond directly to milk fat depression.
本研究的目的是确定日粮脂肪来源对十二指肠流量、表观吸收率以及反式C18:1脂肪酸在乳脂肪中掺入情况的影响。选用4头处于泌乳中后期、安装了瘤胃和十二指肠瘘管的经产荷斯坦奶牛，给它们饲喂一种基础日粮，该日粮含有36%的玉米青贮、24%的苜蓿青贮和40%的精料（干物质基础）。日粮中分别含有0%的补充脂肪（对照日粮）、3.7%的高油酸葵花籽油、3.7%的高亚油酸葵花籽油或3.7%的部分氢化植物起酥油；采用4×4拉丁方设计，每个试验期为3周。与饲喂对照日粮的奶牛相比，饲喂补充脂肪日粮的奶牛十二指肠中反式C18:1的流量更高（分别为283克/天和64克/天）。在饲喂含高油酸和高亚油酸葵花籽油日粮的奶牛中，反式C18:1向十二指肠流量的增加是由于生物氢化不完全所致。饲喂含部分氢化植物起酥油日粮的奶牛中反式C18:1流量的增加很可能源于日粮中的反式C18:1。饲喂对照日粮以及含高油酸葵花籽油、高亚油酸葵花籽油和植物起酥油日粮的奶牛，其乳脂肪率分别为3.48%、3.07%、3.18%和3.38%。饲喂对照日粮和补充脂肪日粮的奶牛，其乳中反式C18:1分别从占总脂肪酸的2.9%增加到11.2%。在所有补充脂肪的日粮中，乳中反式C18:1的含量相同。补充脂肪后，瘤胃和全消化道对有机物、中性洗涤纤维和氮的消化率没有变化。结果表明，乳脂肪降低的奶牛乳中反式C18:1含量增加；然而，乳中过量的反式C18:1不一定直接对应于乳脂肪降低。
