Department of Agricultural Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada.
J Dairy Sci. 2011 Sep;94(9):4636-46. doi: 10.3168/jds.2010-4056.
The objective of this study was to examine the effects of dietary starch source and content in the immediate postpartum period on plasma metabolites and hormones and ovarian follicular development. One of 3 diets was fed in a randomized block design to 40 cows from calving until 70 d in milk. The diets contained 45% alfalfa silage (AS), 45% barley silage (BS), or 41% barley silage and 4% supplemental starch (SS) on a dry matter basis. All diets contained 45% barley-based concentrate and 10% alfalfa hay. Resulting starch levels were 25.2, 23.3, and 26.7% for AS, BS, and SS, respectively. Body condition was scored every other week and dry matter intake and milk yield were recorded daily. Milk samples were obtained weekly and blood samples were taken at calving and then every other week to determine concentrations of glucose, insulin, insulin-like growth factor-1, β-hydroxybutyrate, and nonesterified fatty acids. Transrectal ultrasonography was performed twice per week from 7 d after calving until first ovulation or 62 d in milk in all cows. For a subset of 7 AS-, 8 BS-, and 9 SS-fed cows, a complete estrous cycle was monitored for ovarian dynamics, and blood samples were collected every second day for progesterone and estradiol. Luteinizing hormone pulsatility was also determined (5 cows/treatment) approximately 15 d postcalving. Treatment had no effect on body condition score, dry matter intake, blood metabolites, milk yield, or milk fat and protein contents, but BS-fed cows had significantly higher levels of milk urea nitrogen compared with SS cows. Cows fed SS (31 d) tended to have a shorter interval from calving to first ovulation than cows fed AS (43 d) or BS (38 d). The incidence of double first ovulations was higher in cows fed SS (46%) compared with those fed BS (0%). Treatment had no effect on LH pulse frequency or amplitude, ovarian dynamics, or progesterone and estradiol concentrations during the observed estrous cycle. Energy balance did not differ among cows fed the 3 diets. Overall, dietary starch source and concentration had little effect on productivity or metabolic status of postpartum cows.
本研究旨在探讨产后早期不同淀粉来源和含量对血浆代谢物和激素及卵巢卵泡发育的影响。40 头奶牛在产后至泌乳 70d 期间，采用随机区组设计，饲喂 3 种日粮，分别为：苜蓿青贮（AS）、大麦青贮（BS）和含 41%大麦青贮和 4%补充淀粉（SS）的日粮。所有日粮均以干物质基础含有 45%的大麦基浓缩料和 10%的苜蓿干草。AS、BS 和 SS 的淀粉水平分别为 25.2%、23.3%和 26.7%。每隔两周记录体况评分，每天记录干物质采食量和产奶量。每周采集奶样，产后每隔两周采血，测定血糖、胰岛素、胰岛素样生长因子-1、β-羟丁酸和非酯化脂肪酸浓度。所有奶牛从产后第 7d 开始，每周经直肠超声检查 2 次，直至首次排卵或泌乳 62d。在 7 头 AS 组、8 头 BS 组和 9 头 SS 组奶牛中，监测完整发情周期的卵巢动态，每隔 2d 采集 1 次血样，测定孕酮和雌二醇浓度。大约产后 15d 时，还测定了 5 头/处理的促黄体激素脉冲频率。处理对体况评分、干物质采食量、血液代谢物、产奶量或乳脂和乳蛋白含量均无影响，但 BS 组奶牛的乳尿素氮水平显著高于 SS 组。与 AS 组（43d）或 BS 组（38d）相比，SS 组奶牛从产犊到首次排卵的间隔时间更短（31d）。SS 组奶牛（46%）的双首次排卵发生率高于 BS 组（0%）。处理对发情周期内 LH 脉冲频率或幅度、卵巢动态或孕酮和雌二醇浓度均无影响。3 种日粮的奶牛能量平衡无差异。总之，日粮淀粉来源和浓度对产后奶牛的生产性能或代谢状态影响不大。
