The study was conducted to provide basic data of corn silage which suitable for the roughage resources in China and different stages of growth and lactation dairy cows TMR grading standard, as a result of the poor roughage resources and coarse silage widely existed in China. The experiment screened the corn silage and TMR samples from the large-scale dairy farm in Beijing area and determined the conventional nutrients, and compared the particle size and raton NDF of the feed with recommendations of Penn State Particle Size Separator(PSPS). By comparison, we found that the particle size of corn silage are generally coarse, and the feedratio value on the first sieve was much more than 3％～5％, which was the recommended value of the PSPS. Most of the fresh cow and high-producing cow's TMR feed ratio on the first sieve exceeded 8％, the feed ratio on the second sieve was lower than the recommened values of the PSPS 15％～25％, possibly because of long particles in the roughage(silage and hay). The NDF contents of fresh cow and high-producing cow's rations were 35％～42％, basically in the low-yield dairy cow 's total ration NDF interval of the rnrecommened values of the PSPS, which were concemed with the limited resources of roughage, low quality, the length of roughage.Thus, the dairy farm in China can not copy the TMR standards of PSPS, we should be based on China's national conditions of roughage, and set up silage which suitable for the roughage resources in China and different stages of growth and lactation dairy cows TMR grading standard.%针对我国粗饲料资源较差以及广泛存在的青贮铡切较长等现实问题,本研究旨在为制定适合于中国饲料资源条件的青贮以及不同生长和泌乳阶段奶牛的TMR分级标准提供基础数据.本试验对北京地区规模化奶牛场的玉米青贮和TMR样品进行颗粒度筛分和常规营养成分测定,并与美国宾州颗粒度分级筛(PSPS)的TMR颗粒度和日粮NDF推荐值进行比较.通过比对发现我国玉米青贮的饲料颗粒度普遍偏大,第一层筛网上的饲料比例远超过宾州筛3%～5%的推荐值.新产牛和高产牛TMR样品位于第一层筛网上的饲料比例绝大多数超过了8%,第二层筛网上的饲料比例比美国推荐值要低15%～25%,这可能是由于粗饲料(青贮和干草)颗粒度过长造成的.高产牛和新产牛日粮NDF含量处于35%～42%,基本上在美国宾州筛推荐的中低产奶牛日粮的NDF范围,这与我国的粗饲料资源有限、质量不高、粗饲料铡切长度有关.因而,我国牧场不能照搬美国宾州筛的TMR分级标准,而应根据我国粗饲料的国情,制订适合于中国饲料资源条件的青贮与不同生长和泌乳阶段奶牛的TMR分级标准.
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