Reynolds C K, Cammell S B, Humphries D J, Beever D E, Sutton J D, Newbold J R
Centre for Dairy Research, Department of Agriculture, University of Reading, Earley Gate, Reading RG6 6AJ England.
J Dairy Sci. 2001 Oct;84(10):2250-9. doi: 10.3168/jds.S0022-0302(01)74672-3.
Two experiments were conducted to determine effects of postrumen starch infusion on milk production and energy and nitrogen utilization in lactating dairy cows. In experiment 1, four cows in early lactation fed grass silage and concentrates were continuously infused into the duodenum with water or 700, 1400, or 2100 g of purified maize starch daily for 10 to 12 d in a 4 x 4 Latin square design with 2-wk periods. Starch infusion increased milk yield linearly and decreased milk fat concentration in a quadratic manner such that increases in fat-corrected milk and calculated milk energy yield were minimal except at the highest rate of infusion. Changes in milk energy output suggest that even at the highest infusion rate metabolizable energy supplied by infused starch was used for tissue energy or oxidized. In experiment 2 energy and nitrogen balance were measured in four cows in late lactation fed a mixture of dehydrated lucerne, grass silage, and concentrates during the last 6 d of 2-wk abomasal infusions of 1200 g of purified wheat starch daily or water in a balanced switchback design with 5-wk periods. Measurements of fecal starch concentration indicated nearly all the starch infused was digested, but decreased fecal pH and apparent nitrogen digestion suggested an increase in hindgut starch fermentation. Starch infusion decreased urine nitrogen output in part because of increased tissue nitrogen retention but had no effect on milk nitrogen output. In absolute terms, numerical decreases in feed energy intake and energy digestion reduced the recovery of starch energy infused as digestible and metabolizable energy, but in terms of changes in total energy supply with starch infusion, 79% was recovered as metabolizable energy. Starch infusion had no effects on heat or milk energy but increased net energy for lactation due to a numerical increase in tissue energy, implying that in late-lactation cows, starch digested postruminally was used with high efficiency for tissue energy retention as protein and fat.
进行了两项试验，以确定瘤胃后淀粉灌注对泌乳奶牛产奶量以及能量和氮利用的影响。在试验1中，4头处于泌乳早期、采食青贮牧草和精料的奶牛，按照4×4拉丁方设计，在为期2周的周期内，连续10至12天每天向十二指肠灌注水或700、1400或2100克纯化玉米淀粉。淀粉灌注使产奶量呈线性增加，乳脂率呈二次曲线下降，以至于除了最高灌注率外，校正乳和计算的乳能量产量的增加最小。乳能量输出的变化表明，即使在最高灌注率下，灌注淀粉提供的可代谢能量也用于组织能量或被氧化。在试验2中，4头处于泌乳后期的奶牛，采食脱水苜蓿、青贮牧草和精料的混合物，在为期5周的周期内，按照平衡折返设计，在为期2周的真胃灌注的最后6天，每天灌注1200克纯化小麦淀粉或水。粪便淀粉浓度的测定表明，几乎所有灌注的淀粉都被消化，但粪便pH值下降和表观氮消化率降低表明后肠淀粉发酵增加。淀粉灌注部分降低了尿氮输出，这是由于组织氮保留增加，但对乳氮输出没有影响。从绝对值来看，饲料能量摄入量和能量消化率的数值下降降低了灌注淀粉作为可消化和可代谢能量的能量回收率，但就淀粉灌注导致的总能量供应变化而言，79%的能量以可代谢能量的形式回收。淀粉灌注对热或乳能量没有影响，但由于组织能量的数值增加，泌乳净能量增加，这意味着在泌乳后期的奶牛中，瘤胃后消化的淀粉被高效地用于以蛋白质和脂肪形式保留组织能量。
