Chung Y-H, Brown N E, Martinez C M, Cassidy T W, Varga G A
Department of Dairy and Animal Science, The Pennsylvania State University, University Park 16802, USA.
J Dairy Sci. 2009 Jun;92(6):2729-36. doi: 10.3168/jds.2008-1299.
A 6 x 6 Latin square design was used to test 3 sets of comparisons simultaneously to study response in dry matter intake, milk yield, and blood parameters to propylene glycol (PG) supplementation delivered by 2 methods [incorporating PG into the total mixed ration (TMR) vs. top dressing; comparison I]; individual or combined dietary choline and PG supplementation as a 2 x 2 factorial (comparison II); or increasing amounts of dietary choline (comparison III). Six multiparous (lactation number = 1.5 +/- 0.8 SD) Holstein dairy cows were at 41 d in milk (+/- 9 SD) at the start of the experiment. Propylene glycol used was a dry product containing 65% PG, and choline was a rumen-protected choline product (RPC; estimated to be 50% rumen-protected) containing 50% choline chloride. In comparison I, treatments compared were 1) control: no PG; 2) PG-TMR: 250 g/d of dry PG (corresponding to 162.5 g/d of PG) incorporated into the TMR; and 3) PG-top dress: 250 g/d of dry PG top-dressed onto the TMR. In comparison II, treatments compared were 1) control: no PG and no RPC; 2) PG: 250 g/d of dry PG incorporated into the TMR; 3) RPC: 50 g/d of RPC top-dressed onto the TMR; and 4) PG+RPC: combination of treatments 2 and 3. In comparison III, treatments compared were 0, 25, and 50 g/d of RPC top-dressed onto the TMR. Each experimental period lasted 10 d with 9 d of adaptation followed by 1 d of serial blood sampling. Dry matter intake and milk yield were recorded daily. During the serial blood sampling, jugular blood was sampled every 20 min for the first 4 h and at 8 and 12 h after treatment administration. Results obtained from comparison I showed that feeding 250 g/d of PG as a dry product decreased plasma beta-hydroxybutyrate (BHBA) concentration (mean +/- SEM) from 701 +/- 81 (control) to 564 +/- 76 micromol/L without affecting serum insulin, plasma glucose, or plasma nonesterified fatty acid concentrations. Top-dressing PG decreased plasma BHBA concentrations more than by incorporating it into the TMR [527 vs. 601 micromol/L (+/- 81 pooled SEM)]. Results obtained from comparison II showed that supplementing choline as RPC, PG, or both had no effect on dry matter intake, milk yield, or any of the blood parameters measured. Results obtained from comparison III showed that milk yield tended to increase linearly with increasing amounts of dietary choline as RPC. We concluded that feeding PG as a dry product reduced plasma BHBA concentration but top-dressing PG was more efficient at reducing plasma BHBA level than incorporating PG into the TMR. Dietary choline as RPC tended to increase milk yield linearly. However, a combined effect of dietary PG and choline was not evident and therefore not beneficial.
采用6×6拉丁方设计，同时测试3组比较，以研究干物质采食量、产奶量和血液参数对通过2种方法添加丙二醇（PG）的反应[将PG掺入全混合日粮（TMR）与撒施；比较I]；作为2×2析因设计的单独或联合日粮胆碱和PG添加（比较II）；或增加日粮胆碱量（比较III）。6头经产（泌乳次数=1.5±0.8标准差）荷斯坦奶牛在实验开始时处于产奶41天（±9标准差）。所用丙二醇为含65%PG的干燥产品，胆碱为瘤胃保护性胆碱产品（RPC；估计50%为瘤胃保护性），含50%氯化胆碱。在比较I中，比较的处理为：1）对照：不添加PG；2）PG-TMR：将250 g/d干燥PG（相当于162.5 g/d PG）掺入TMR；3）PG-撒施：将250 g/d干燥PG撒施到TMR上。在比较II中，比较的处理为：1）对照：不添加PG和不添加RPC；2）PG：将250 g/d干燥PG掺入TMR；3）RPC：将50 g/d RPC撒施到TMR上；4）PG+RPC：处理2和3的组合。在比较III中，比较的处理为向TMR上撒施0、25和50 g/d RPC。每个实验期持续10天，先适应9天，随后1天进行连续血液采样。每天记录干物质采食量和产奶量。在连续血液采样期间，颈静脉血在最初4小时每20分钟采样一次，并在给药后8小时和12小时采样。比较I的结果表明，以干燥产品形式饲喂250 g/d PG可使血浆β-羟基丁酸（BHBA）浓度（均值±标准误）从70l±81（对照）降至564±76 μmol/L，而不影响血清胰岛素、血浆葡萄糖或血浆非酯化脂肪酸浓度。撒施PG比将其掺入TMR更能降低血浆BHBA浓度[527对601 μmol/L（±81合并标准误）]。比较II的结果表明，作为RPC、PG或两者补充胆碱对干物质采食量、产奶量或所测任何血液参数均无影响。比较III的结果表明，产奶量倾向于随作为RPC的日粮胆碱量增加而呈线性增加。我们得出结论，以干燥产品形式饲喂PG可降低血浆BHBA浓度，但撒施PG在降低血浆BHBA水平方面比将PG掺入TMR更有效。作为RPC的日粮胆碱倾向于使产奶量呈线性增加。然而，日粮PG和胆碱的联合作用不明显，因此无益处。
