Neutral detergent fiber (NDF), as the main component of structural carbohydrate in forage, is a vital factor impacting the performance of young ruminants. The objective of this study was to evaluate the effect of starter NDF level on the rumen fermentation and morphometrics of lambs fed isocaloric and isonitrogenous diets. One hundred Hu sheep lambs (18 days of age and 6.1 ± 0.1 kg body weight [BW]) were randomly assigned to one of the four starter diets differing in their NDF levels on a dry matter (DM) basis: 1) diet with 14% NDF (NDF14), 2) diet with 18% NDF (NDF18), 3) diet with 22% NDF (NDF22), and 4) diet with 26% NDF (NDF26). Lambs were fed milk replacer with designed starters from 21 to 60 d of age and then transitioned to the same starter feed until 90 d of age. Six lambs from each treatment (close to the average BW of the corresponding treatment) were selected and slaughtered at 90 d of age for measuring rumen fermentation, anatomical development, and morphometric characteristics. Lambs receiving NDF22 and NDF26 starter diets had greater (P < 0.05) intake of starter and total DM, and average daily gain during the overall period, thereby heavier (P < 0.05) final weights at 90 d of age compared with those fed NDF14 starter diet. At 90 d of age, lambs fed NDF22 and NDF26 starters had higher rumen pH, followed by lower propionate, higher acetate concentrations (P < 0.05), and a higher acetate-to-propionate ratio compared with those fed NDF14 and NDF18 starters (P < 0.05). No significant differences of the full and empty weight of reticulorumen were observed among treatments; however, the reticulorumen weight expressed as a percentage of the complex stomach weight was lower (P < 0.05) in lambs fed NDF22 and NDF26 starters compared with those fed NDF14 starter. Furthermore, NDF14 lambs had the thickest keratin layer and epithelium compared with those in the other treatments but showed the thinnest muscle layer (P < 0.05). These results suggest that increasing starter NDF levels can ameliorate the rumen fermentation environment and alleviate hyperkeratosis and plaque formation in the rumen epithelium. In summary, including 22% and 26% NDF in the pelleted starter can improve the performance of lambs.

中文翻译：

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发酵剂NDF水平对等热量和等氮饮食羔羊生长性能和瘤胃发育的影响。

中性洗涤剂纤维（NDF）作为草料中结构性碳水化合物的主要成分，是影响年轻反刍动物性能的重要因素。这项研究的目的是评估发酵剂NDF水平对饲喂等热量和等氮饮食的羔羊的瘤胃发酵和形态测定的影响。将一百只胡绵羊羔羊（18天大，体重6.1±0.1千克体重[BW]）随机分配到四种干粮（DM）中其NDF水平不同的起始日粮之一：1）日粮中添加了14种日粮％NDF（NDF14），2）18％NDF（NDF18）的饮食，3）22％NDF（NDF22）的饮食和4）26％NDF（NDF26）的饮食。给羔羊饲喂设计了21至60 d发酵剂的代乳品，然后过渡到相同的发酵剂，直至90 d。从每种处理中选择六只羔羊（接近相应处理的平均体重），并在90 d处宰杀，以测量瘤胃发酵，解剖发育和形态特征。接受NDF22和NDF26起始日粮的羔羊的起始日粮和总DM摄入量更高（P <0.05），并且在整个时期内平均日增重，因此与饲喂NDF14起始日粮的羔羊相比，在90 d龄时的最终体重增加（P <0.05）饮食。在90 d龄时，饲喂NDF22和NDF26发酵剂的羔羊的瘤胃pH值较高，其丙酸盐含量较低，乙酸盐浓度更高（P <0.05），而饲喂NDF14和NDF18发酵剂的羔羊的乙酸/丙酸比例更高（P <0.05）。各处理之间网状网的总重量和空置重量没有显着差异；然而，与饲喂NDF14的羔羊相比，饲喂NDF22和NDF26的羔羊的网状组织重量以复合胃重量的百分比表示较低（P <0.05）。此外，与其他处理相比，NDF14羔羊的角蛋白层和上皮最厚，但肌肉层最薄（P <0.05）。这些结果表明，增加起始NDF含量可以改善瘤胃发酵环境，并减轻瘤胃上皮的过度角化和斑块形成。总之，在粒状发酵剂中包含22％和26％的NDF可以改善羔羊的性能。与其他处理相比，NDF14羔羊的角蛋白层和上皮最厚，但肌肉层最薄（P <0.05）。这些结果表明，增加起始NDF含量可以改善瘤胃发酵环境，并减轻瘤胃上皮的过度角化和斑块形成。总之，在粒状发酵剂中包含22％和26％的NDF可以改善羔羊的性能。与其他处理相比，NDF14羔羊的角蛋白层和上皮最厚，但肌肉层最薄（P <0.05）。这些结果表明，增加起始NDF含量可以改善瘤胃发酵环境，并减轻瘤胃上皮的过度角化和斑块形成。总之，在粒状发酵剂中包含22％和26％的NDF可以改善羔羊的性能。