Institute of Animal Nutrition and Physiology, Christian-Albrechts-Universität zu Kiel, 24118 Kiel, Germany.
Institute of Animal Nutrition and Physiology, Christian-Albrechts-Universität zu Kiel, 24118 Kiel, Germany.
J Dairy Sci. 2018 Feb;101(2):1216-1226. doi: 10.3168/jds.2017-13605. Epub 2017 Dec 14.
The objectives of this study were to evaluate the effects of replacing maize silage plus soybean meal with red clover silage (RCS) plus wheat on feed intake, diet digestibility, N partitioning, urinary excretion of purine derivatives, and milk production in dairy cows. Forty-four lactating German Holstein cows were used in a 4 × 4 Latin square design with 21-d periods composed of a 13-d adaptation phase followed by an 8-d sampling phase. Experimental diets offered as total mixed ration consisted of a constant forage-to-concentrate ratio (75:25) with targeted proportions of RCS-to-maize silage of 15:60 (RCS), 30:45 (RCS), 45:30 (RCS), and 60:15 (RCS) on a dry matter (DM) basis. Increasing the proportion of RCS plus wheat in the diet decreased linearly the intake of DM from 22.4 to 19.8 kg/d, and of organic matter from 21.1 to 18.1 kg/d. The apparent total tract digestibility (ATTD) of DM and organic matter did not differ across diets and averaged 68.4 and 70.5%, respectively. However, ATTD of N decreased linearly from 68.5 to 63.2%, whereas ATTD of neutral detergent fiber and acid detergent fiber increased linearly from 50.4 to 59.6% and from 48.4 to 57.7%, respectively, when increasing the proportion of RCS plus wheat. Fecal N excretion increased from 31.6 (RCS) to 37.2% (RCS) of N intake, whereas urinary N excretion was the lowest (32.8% of N intake) with RCS. Hence, N efficiency (milk N/N intake) decreased linearly with incremental levels of RCS plus wheat, being the lowest when feeding RCS (25.4%), probably due to increased nonprotein N proportion in total dietary N. Urinary excretion of purine derivatives decreased linearly from 378 to 339 mmol/d, which suggests that increasing levels of RCS plus wheat reduced the microbial crude protein flow at the duodenum. Milk yield and milk protein concentration declined linearly from 35.9 to 30.2 kg/d and from 3.20 to 3.01%, respectively, when increasing the proportion of RCS plus wheat. In conclusion, caution should be taken before introducing high levels of RCS plus wheat in diets of high-yielding dairy cows. However, RCS plus wheat can be included up to 30% of the dairy cow diet (DM basis) without a reduction in lactation performance.
本研究旨在评估用红三叶草青贮（RCS）加小麦替代玉米青贮和豆粕对奶牛采食量、日粮消化率、氮分配、尿嘌呤衍生物排泄和产奶量的影响。44 头泌乳德系荷斯坦奶牛采用 4×4 拉丁方设计，21d 期由 13d 适应期和 8d 采样期组成。试验日粮为全混合日粮，粗饲料与精饲料的比例固定（75:25），RCS 与玉米青贮的比例分别为 15:60（RCS）、30:45（RCS）、45:30（RCS）和 60:15（RCS）（干物质基础）。随着日粮中 RCS 加小麦比例的增加，奶牛的 DM 和有机物采食量分别线性下降 12.2%和 10.7%，从 22.4kg/d 和 21.1kg/d 降至 19.8kg/d 和 18.1kg/d。DM 和有机物的表观全肠道消化率（ATTD）在各处理间无差异，分别为 68.4%和 70.5%。然而，氮的 ATTD 线性下降，从 68.5%降至 63.2%，而中性洗涤纤维和酸性洗涤纤维的 ATTD 则分别线性上升，从 50.4%升至 59.6%和从 48.4%升至 57.7%。当 RCS 加小麦的比例增加时，粪便氮排泄量从 31.6%（RCS）增加到 37.2%（RCS），而尿氮排泄量最低（氮摄入量的 32.8%），这与 RCS 有关。因此，随着 RCS 加小麦水平的增加，氮效率（奶氮/N 摄入量）呈线性下降，当饲喂 RCS 时最低（25.4%），这可能是由于日粮总氮中非蛋白氮的比例增加。尿嘌呤衍生物的排泄量从 378mmol/d 线性下降到 339mmol/d，这表明随着 RCS 加小麦水平的增加，减少了十二指肠微生物粗蛋白的流量。产奶量和乳蛋白浓度分别从 35.9kg/d 线性下降到 30.2kg/d 和从 3.20%线性下降到 3.01%。总之，在高产奶牛日粮中引入高水平的 RCS 加小麦时应谨慎。然而，RCS 加小麦的添加量可达到奶牛日粮的 30%（干物质基础）而不会降低泌乳性能。
