US Dairy Forage Research Center, USDA-ARS, Madison, WI 53706, USA.
J Dairy Sci. 2010 Jan;93(1):311-22. doi: 10.3168/jds.2009-2552.
Thirty-eight lactating dairy cows including 6 ruminally cannulated cows were used in a feeding study to assess effects of feed sources that differed in dietary nonfiber carbohydrate (NFC) composition and ruminal degradability of dietary protein (RDP) on production, ruminal, and plasma measures. The design was a partially balanced, incomplete Latin square with three 21-d periods and a 3 x 2 factorial arrangement of treatments. Samples and data were collected in the last 7 d of each period. Feed sources that differed in NFC profile were dry ground corn (GC; starch), dried citrus pulp (DCP; sugar and pectins), and sucrose+molasses (SM; sugar). Dietary RDP was altered by providing CP with soybean meal (+RDP) or substituting a heat-treated expeller soybean product for a portion of the soybean meal (-RDP). Diets were formulated to be isonitrogenous and similar in NFC concentration. Cows consuming GC had the greatest milk urea nitrogen and milk protein percentage and yield, tended to have the greatest dry matter intake, but had a lesser milk fat percentage compared with cows consuming DCP and SM. Sucrose+molasses diets supported greater dry matter intake, milk protein yield, and 3.5% fat- and protein-corrected milk yield than did DCP diets. On -RDP diets, milk protein percentage was less and milk urea nitrogen and protein yield tended to be less than for +RDP diets. Dry ground corn diverged from DCP and SM in the effect of NFC x RDP, with cows consuming GC having lesser milk yield, 3.5% fat- and protein-corrected milk yield, and efficiency with -RDP as compared with +RDP, whereas these production measures were greater with -RDP than +RDP for cows consuming DCP and SM. In contrast, in situ NDF digestibility at 30h for GC and SM was greater for -RDP as compared with +RDP, but the reverse was true for DCP. The lowest ruminal pH detected by 6h postfeeding was also influenced by the interaction of NFC x RDP, with cows consuming SM having a lower pH with +RDP than with -RDP and cows consuming DCP having a similar pH on either RDP treatment. Total rumen volatile fatty acid concentrations did not differ among diets, but acetate molar percent was greater for DCP than for SM, and GC had the lowest molar percent for butyrate and valerate and greatest branched-chain volatile fatty acid concentration. Valerate molar percent and NH(3) concentration tended to be greater with +RDP than with -RDP. Plasma glucose and insulin were both greater in cows receiving SM than in those receiving DCP. Protein degradability, NFC source, and their interactions affected lactation, ruminal, and blood measures, suggesting that these dietary factors warrant further consideration in diet formulation.
三十八头泌乳奶牛，包括 6 头瘤胃可插管奶牛，用于一项饲养研究，以评估不同非纤维碳水化合物 (NFC) 组成和瘤胃可降解蛋白 (RDP) 的饲料源对生产、瘤胃和血浆指标的影响。设计为部分平衡、不完全拉丁方，有三个 21 天周期和处理的 3 x 2 因子排列。在每个周期的最后 7 天收集样本和数据。NFC 特征不同的饲料源是干磨玉米（GC；淀粉）、干柑橘渣（DCP；糖和果胶）和蔗糖+糖蜜（SM；糖）。通过提供含有大豆粉的 CP（+RDP）或用热处理的榨油大豆产品代替部分大豆粉（-RDP）来改变日粮 RDP。日粮的配方为等氮和相似的 NFC 浓度。与 DCP 和 SM 相比，食用 GC 的奶牛的牛奶尿素氮和牛奶蛋白百分率最高，牛奶干物质摄入量最高，但牛奶脂肪百分率较低。与 DCP 日粮相比，蔗糖+糖蜜日粮支持更高的干物质摄入量、牛奶蛋白产量和 3.5%乳脂和蛋白校正乳产量。在 -RDP 日粮中，牛奶蛋白百分率较低，牛奶尿素氮和蛋白产量往往低于 +RDP 日粮。与 DCP 和 SM 相比，干磨玉米在 NFC x RDP 的影响上与 DCP 和 SM 不同，与 +RDP 相比，食用 GC 的奶牛的牛奶产量、3.5%乳脂和蛋白校正乳产量以及效率较低，而 DCP 和 SM 则随着 -RDP 的摄入而增加。相比之下，GC 和 SM 在 30h 时的原位 NDF 消化率在 -RDP 时高于 +RDP，但 DCP 则相反。6h 后检测到的最低瘤胃液 pH 值也受到 NFC x RDP 的相互作用的影响，与 -RDP 相比，食用 SM 的奶牛的 pH 值较低，而食用 DCP 的奶牛的 pH 值在两种 RDP 处理中相似。日粮之间的总瘤胃挥发性脂肪酸浓度没有差异，但 DCP 的乙酸摩尔百分比高于 SM，GC 的丁酸和戊酸摩尔百分比最低，支链挥发性脂肪酸浓度最高。与 -RDP 相比，戊酸摩尔百分比和 NH(3)浓度往往更高。接受 SM 的奶牛的血糖和胰岛素都高于接受 DCP 的奶牛。蛋白降解率、NFC 源及其相互作用影响泌乳、瘤胃和血液指标，表明这些饮食因素值得在日粮配方中进一步考虑。
