ABSTRACT The objective of the present study was to evaluate the effect of different doses of narasin on dry matter intake (DMI), milk production and composition in ewes and growth performance of their lambs. Forty crossbred lactating ewes Dorper vs. Santa Ines (54.4 ± 1.7 kg of initial BW; mean ± SD) were penned individually with their lambs and used in a randomized complete block design with 10 blocks and 4 treatments. Ewes were fed a basal diet (168 ± 0.003 g/kg DM of CP) containing 50% concentrate and 50% Brachiaria brizantha hay. The treatments were as follows: 0 N - control diet (basal diet without addition narasin); 13 N - addition of 13 mg/kg DM of narasin; 20 N - addition of 20 mg/kg DM of narasin; 27 N - addition of 27 mg/kg DM of narasin. Once a week, from the second to tenth week of lactation (weaning time), ewes were separated from their lambs, injected with oxytocin, and mechanically milked to empty mammary gland. After 3 hours, the same procedure was repeated, milk production was recorded and samples collected for milk composition analysis. Ewes were weighed for 3 consecutive days at the beginning and end of the experiment. Lambs growth performance was evaluated weekly. The data were analyzed using a linear or quadratic polynomial contrast in SAS. There was a quadratic effect (P = 0.03) of narasin on milk production, in which ewes fed the diet containing 13 mg/kg DM had the highest production (194.9 g/3 hours) Narasin inclusion decreased linearly the percentage of protein (P = 0.01), non-fat solids (P = 0.03), and SCC (P = 0.04) in milk. The fat, lactose and total solids content were not affected by treatments. There was a quadratic effect (P = 0.05) of narasin doses on concentrate intake by the lambs, in which the lowest intake was observed for lambs from ewes fed N13. The supply of narasin did not affect the ADG and final BW of the lambs. In conclusion, the use of 13 mg/kg DM of narasin was the best concentration in diets containing 50% forage and 50% concentrate for lactating ewes, due to positive effect on milk production. The inclusion of values higher than 20 mg/kg DM of narasin is not recommended, because this content drastically reduced DMI and milk production, resulting in greater concentrate intake by lambs with no effect on ADG and final BW.

中文翻译：

---

narasin 在哺乳母羊日粮中的应用

摘要 本研究的目的是评估不同剂量的 narasin 对母羊的干物质摄入量 (DMI)、产奶量和成分以及羔羊生长性能的影响。40 头杂交泌乳母羊 Dorper 与 Santa Ines（初始体重 54.4 ± 1.7 kg；平均值 ± SD）与羔羊单独圈养，并用于随机完整区组设计，包括 10 个区组和 4 个处理。给母羊喂食含有 50% 浓缩物和 50% Brachiaria brizantha 干草的基础日粮（168 ± 0.003 g/kg DM CP）。处理如下： 0 N-对照饮食（没有添加 narasin 的基础饮食）；13 N - 添加 13 mg/kg DM 的 narasin；20 N - 添加 20 mg/kg DM 的 narasin；27 N - 添加 27 mg/kg DM 的 narasin。每周一次，从泌乳第二周到第十周（断奶时间），将母羊与羔羊分开，注射催产素，并通过机械挤奶以排空乳腺。3 小时后，重复相同的程序，记录产奶量并收集样品用于牛奶成分分析。母羊在实验开始和结束时连续 3 天称重。每周评估羔羊的生长性能。在 SAS 中使用线性或二次多项式对比分析数据。narasin 对产奶量呈二次方效应 (P = 0.03)，其中饲喂含 13 mg/kg DM 的日粮的母羊产奶量最高 (194.9 g/3 小时) Narasin 加入量线性降低蛋白质百分比 (P = 0.01)、牛奶中的非脂肪固体 (P = 0.03) 和 SCC (P = 0.04)。脂肪、乳糖和总固体含量不受处理的影响。存在二次效应（P = 0。05) 羔羊精料摄入量的 narasin 剂量，其中观察到最低摄入量来自喂养 N13 的母羊的羔羊。narasin的供应不影响羔羊的ADG和最终BW。总之，由于对产奶量的积极影响，在含有 50% 草料和 50% 浓缩物的日粮中使用 13 mg/kg DM 的 narasin 是泌乳母羊的最佳浓度。不建议包含高于 20 mg/kg DM 的 narasin 值，因为该含量会显着降低 DMI 和产奶量，导致羔羊摄入更多精料，而对 ADG 和最终 BW 没有影响。由于对产奶量的积极影响，在含有 50% 草料和 50% 浓缩物的日粮中使用 13 mg/kg DM 的 narasin 是最佳浓度。不推荐包含高于 20 mg/kg DM 的 narasin 值，因为该含量会显着降低 DMI 和产奶量，导致羔羊摄入更多精料，而对 ADG 和最终 BW 没有影响。由于对产奶量的积极影响，在含有 50% 草料和 50% 浓缩物的日粮中使用 13 mg/kg DM 的 narasin 是最佳浓度。不建议包含高于 20 mg/kg DM 的 narasin 值，因为该含量会显着降低 DMI 和产奶量，导致羔羊摄入更多精料，而对 ADG 和最终 BW 没有影响。