Robinson P H, McQueen R E
Atlantic Dairy and Forage Institute, Fredericton Junction, NB, Canada.
J Dairy Sci. 1997 Apr;80(4):681-91. doi: 10.3168/jds.S0022-0302(97)75987-3.
Nine midlactation dairy cows were offered one of three mixed silage rations with neutral detergent fiber (NDF) that was similar in concentration but different in fermentability. Differences in fermentability were achieved by substituting a high quality alfalfa silage for a low quality alfalfa silage and substituting a combination of ryegrass and timothy silages for a barley silage. In addition, concentrate was allocated at 0.30, 0.82, or 1.37 kg of dry matter/kg of dry matter intake (DMI) from the mixed silage ration. As expected, the NDF content of the mixed silage ration did not differ, although fermentability of NDF increased numerically as forage quality increased. Intake of NDF increased linearly, and DMI tended to increase linearly, as fiber fermentability of the mixed silage ration increased. In addition, cows produced more milk, milk fat, and milk protein and generated more total and milk energy. The calculated concentration of net energy for lactation of the total diet also increased. Results support the concept that NDF quality influences and can be used to predict voluntary feed intake, at least in relatively high producing dairy cows. The DMI increased, and intake of NDF and crude protein declined, as the allocation of concentrate increased. In addition, as concentrate allocation increased, cows spent less time eating and ruminating and more time resting and produced more milk, milk protein, and milk lactose. Cows also generated more total energy and milk energy, although, despite a sharp decrease in the forage proportion of the diet, the calculated energy density of the diet did not differ among concentrate levels. The lack of significant interactions between concentrate level and fiber fermentability for any parameter measured supports the contention that high quality forage is critical to a successful dairy ration, regardless of the proportion of forage in the diet.
九头处于泌乳中期的奶牛被给予三种混合青贮日粮中的一种，这些日粮的中性洗涤纤维（NDF）浓度相似但发酵性不同。通过用高质量苜蓿青贮替代低质量苜蓿青贮，并用黑麦草和梯牧草青贮的组合替代大麦青贮来实现发酵性的差异。此外，根据混合青贮日粮中干物质摄入量（DMI）的0.30、0.82或1.37千克干物质/千克干物质的比例分配精饲料。正如预期的那样，混合青贮日粮的NDF含量没有差异，尽管随着饲草质量的提高，NDF的发酵性在数值上有所增加。随着混合青贮日粮纤维发酵性的提高，NDF摄入量呈线性增加，DMI也呈线性增加趋势。此外，奶牛产奶量、乳脂和乳蛋白增加，总能量和乳能量也增加。计算得出的全日粮泌乳净能量浓度也有所增加。结果支持这样的观点，即NDF质量会影响并可用于预测自愿采食量，至少对于产奶量相对较高的奶牛是这样。随着精饲料分配量的增加，DMI增加，NDF和粗蛋白摄入量下降。此外，随着精饲料分配量的增加，奶牛进食和反刍的时间减少，休息时间增加，产奶量、乳蛋白和乳糖增加。奶牛产生的总能量和乳能量也更多，尽管日粮中饲草比例大幅下降，但不同精饲料水平下日粮的计算能量密度没有差异。所测任何参数在精饲料水平和纤维发酵性之间均无显著交互作用，这支持了这样的观点，即无论日粮中饲草比例如何，高质量饲草对于成功的奶牛日粮至关重要。
