Bahrami-Yekdangi H, Khorvash M, Ghorbani G R, Alikhani M, Jahanian R, Kamalian E
Department of Animal Science, Isfahan University of Technology, Isfahan 84156, Iran.
Department of Animal Science, Isfahan University of Technology, Isfahan 84156, Iran.
J Dairy Sci. 2014;97(6):3707-14. doi: 10.3168/jds.2013-6725. Epub 2014 Mar 27.
This study was conducted to evaluate the effects of decreasing dietary protein and rumen-undegradable protein (RUP) on production performance, nitrogen retention, and nutrient digestibility in high-producing Holstein cows in early lactation. Twelve multiparous Holstein lactating cows (2 lactations; 50 ± 7 d in milk; 47 kg/d of milk production) were used in a Latin square design with 4 treatments and 3 replicates (cows). Treatments 1 to 4 consisted of diets containing 18, 17.2, 16.4, and 15.6% crude protein (CP), respectively, with the 18% CP diet considered the control group. Rumen-degradable protein levels were constant across the treatments (approximately 10.9% on a dry matter basis), whereas RUP was gradually decreased. All diets were calculated to supply a postruminal Lys:Met ratio of about 3:1. Dietary CP had no significant effects on milk production or milk composition. In fact, 16.4% dietary CP compared with 18% dietary CP led to higher milk production; however, this effect was not significant. Feed intake was higher for 16.4% CP than for 18% CP (25.7 vs. 24.3 kg/d). Control cows had greater CP and RUP intakes, which resulted in higher concentrations of plasma urea nitrogen and milk urea nitrogen; cows receiving 16.4 and 15.6% CP, respectively, exhibited lower concentrations of milk urea nitrogen (15.2 and 15.1 vs. 17.3 mg/dL). The control diet had a significant effect on predicted urinary N. Higher CP digestibility was recorded for 18% CP compared with the other diets. Decreasing CP and RUP to 15.6 and 4.6% of dietary dry matter, respectively, had no negative effects on milk production or composition when the amounts of Lys and Met and the Lys:Met ratio were balanced. Furthermore, decreasing CP and RUP to 16.4 and 5.4%, respectively, increased dry matter intake.
本研究旨在评估降低日粮蛋白质和瘤胃不可降解蛋白（RUP）对高产荷斯坦奶牛泌乳早期生产性能、氮保留和养分消化率的影响。选用12头经产荷斯坦泌乳奶牛（2胎；产奶50±7天；日产奶量47千克），采用4种处理、3个重复（奶牛）的拉丁方设计。处理1至4的日粮粗蛋白（CP）含量分别为18%、17.2%、16.4%和15.6%，其中18%CP日粮为对照组。各处理的瘤胃可降解蛋白水平保持恒定（干物质基础上约为10.9%），而RUP逐渐降低。所有日粮经计算后，瘤胃后赖氨酸：蛋氨酸比例约为3:1。日粮CP对产奶量或乳成分无显著影响。实际上，16.4%日粮CP组的产奶量高于18%日粮CP组；然而，这种影响并不显著。16.4%CP组的采食量高于18%CP组（25.7对24.3千克/天）。对照组奶牛的CP和RUP摄入量更高，导致血浆尿素氮和乳尿素氮浓度更高；分别采食16.4%和15.6%CP的奶牛，乳尿素氮浓度较低（15.2和15.1对17.3毫克/分升）。对照日粮对预测尿氮有显著影响。与其他日粮相比，18%CP日粮的CP消化率更高。当赖氨酸和蛋氨酸的量以及赖氨酸：蛋氨酸比例平衡时，将CP和RUP分别降至日粮干物质的1
