Shingfield Kevin J, Arölä Anu, Ahvenjärvi Seppo, Vanhatalo Aila, Toivonen Vesa, Griinari J Mikko, Huhtanen Pekka
Animal Production Research, MTT Agrifood Research Finland, Jokioinen, FIN 31600, Finland.
J Nutr. 2008 Apr;138(4):710-7. doi: 10.1093/jn/138.4.710.
Ruminal administration of a triple indigestible marker system comprised of cobalt EDTA (CoEDTA), ytterbium acetate (YbAc), and chromium-mordanted straw (CrS) decreases product:substrate ratios for Delta9-desaturase in bovine milk fat. This experiment was designed to identify the marker(s) responsible and develop an alternative system for simultaneous determination of nutrient flow in the gastro-intestinal tract and milk fatty acid composition. Five lactating dairy cows were used in a 5 x 5 Latin square with 21-d periods to evaluate the effects of YbAc, CoEDTA, and CrS independently or as part of a triple marker system (TMS), and CrEDTA as an alternative to CoEDTA on milk fat composition. Markers were administered in the rumen over a 7-d interval and samples of milk were collected on d -1, 3, 7, and 11. Both TMS and CoEDTA alone reduced the concentrations of milk fatty acids containing a cis-9 double bond, whereas YbAc, CrS, and CrEDTA had no effect. Reductions in product:substrate ratios for Delta9-desaturase were time dependent and evident within 3 d of administration. Ruminal infusion of CoEDTA for 7 d induced mean decreases in milk cis-9 14:1/14:0, cis-9 16:1/16:0, cis-9 18:1/18:0, and cis-9, trans-11 conjugated linoleic acid/trans-11 18:1 concentration ratios of 47.7, 26.7, 40.3, and 42.6%, respectively. In conclusion, ruminal infusion of CoEDTA alters milk fatty acid composition and appears to inhibit Delta9-desaturase activity in the bovine mammary gland. Results indicate that a TMS based on CrEDTA, YbAc, and indigestible neutral detergent fiber can be used for estimating nutrient flow without altering milk fat composition in lactating cows.
瘤胃内给予由乙二胺四乙酸钴（CoEDTA）、醋酸镱（YbAc）和铬媒染秸秆（CrS）组成的三重不可消化标记系统，可降低牛乳脂肪中Delta9-去饱和酶的产物:底物比率。本实验旨在确定起作用的标记物，并开发一种替代系统，用于同时测定胃肠道中的养分流量和乳脂肪酸组成。选用5头泌乳奶牛，采用5×5拉丁方设计，每个周期21天，以单独评估YbAc、CoEDTA和CrS的作用，或作为三重标记系统（TMS）的一部分进行评估，同时评估CrEDTA作为CoEDTA的替代品对乳脂肪组成的影响。标记物在瘤胃内每隔7天给予一次，并在第-1、3、7和11天采集乳样。单独的TMS和CoEDTA均降低了含有顺式-9双键的乳脂肪酸浓度，而YbAc、CrS和CrEDTA则无此作用。Delta9-去饱和酶的产物:底物比率降低具有时间依赖性，给药后3天内即可显现。瘤胃内输注CoEDTA 7天，导致乳中顺式-9 14:1/14:0、顺式-9 16:1/16:0、顺式-9 18:1/18:0和顺式-9,反式-11共轭亚油酸/反式-11 18:1浓度比率平均分别降低47.7%、26.7%、40.3%和42.6%。总之，瘤胃内输注CoEDTA会改变乳脂肪酸组成，似乎会抑制牛乳腺中的Delta9-去饱和酶活性。结果表明，基于CrEDTA、YbAc和不可消化中性洗涤纤维的TMS可用于估计泌乳奶牛的养分流量，而不会改变乳脂肪组成。
