The study evaluated the effects of three different theoretical particle lengths (TPL) of grass silage on the distribution of particle fractions of the diet and the resulting effects on fermentation profile and concentrations of protozoa and mixed bacterial mass in the rumen of three lactating Holstein cows fed total mixed rations (45% grass silage, 5% grass hay and 50% concentrate) ad libitum. Decreasing TPL of grass silage (long, medium, short) reduced particles retained on the 19-mm sieve of the Penn State Particle Separator, while particle fractions from 8 mm to 19 mm and smaller than 8 mm were increased. Different TPL did not affect pH and the concentration of volatile fatty acids in the rumen. However, lowering the TPL from long to medium increased significantly the bicarbonate concentration, acetate proportion and protozoal number in the rumen, whereas the proportion of bacterial protein in ruminal digesta and its amino acid concentration were significantly increased by the short TPL. For the current feeding conditions, it can be concluded that increasing the fraction of particles between 8 and 19 mm and probably even the fraction below 8 mm by decreasing TPL of grass silage do not adversely affect rumen conditions and can be beneficial in terms of optimising concentration and activity of ruminal microbiota in high-yielding dairy cows.

中文翻译：

---

评估日粮颗粒组分对饲喂青贮饲料的奶牛瘤胃中发酵曲线和微生物群浓度的影响

该研究评估了三种不同的青贮草理论颗粒长度 (TPL) 对饲料颗粒部分分布的影响，以及由此产生的对三头哺乳期荷斯坦奶牛瘤胃中原生动物和混合细菌质量的发酵曲线和浓度的影响。总混合日粮（45% 青贮草、5% 干草和 50% 浓缩物）随意。降低青贮草（长、中、短）的 TPL 减少了保留在宾夕法尼亚州立大学颗粒分离器 19 毫米筛子上的颗粒，而颗粒部分从 8 毫米增加到 19 毫米和小于 8 毫米。不同的TPL不影响瘤胃的pH值和挥发性脂肪酸的浓度。然而，将 TPL 从长期降低到中等显着增加了碳酸氢盐浓度，短TPL显着增加瘤胃中的醋酸比例和原生动物数，而瘤胃食糜中细菌蛋白质的比例及其氨基酸浓度显着增加。对于目前的饲养条件，可以得出结论，通过降低青贮饲料的 TPL 来增加 8 到 19 毫米之间的颗粒比例，甚至可能增加低于 8 毫米的颗粒比例不会对瘤胃条件产生不利影响，并且有利于优化浓度高产奶牛瘤胃微生物群的活性及活性。