Brandt R T, Klopfenstein T J
J Anim Sci. 1986 Sep;63(3):911-22. doi: 10.2527/jas1986.633911x.
The influence of mechanically separated alfalfa fractions on intake, digestibility and rate of ruminal passage was investigated using 48 lambs (32 kg) in a digestion trial. Whole plant pre-bloom alfalfa (25% crude protein) or fractions (presscake, dehydrated presscake, protein coagulum, dehydrated protein coagulum, whole juice or deproteinized juice) were added to a 3% ammonia (NH3)-treated corn cob negative control diet at levels equal to 20% wholeplant alfalfa dry matter (DM); eight treatments, six lambs/treatment. Ad libitum intake was greater (P less than .05) for alfalfa fiber (presscake) or juice supplemented diets compared with 20% direct cut alfalfa. Dry matter intake, digestibility of DM and cell walls, and rate of passage were highly correlated when diets were fed ad libitum. At equal DM intakes, dehydrated vs wet presscake increased (P less than .05) DM and cell wall digestibility. Heating of the protein may have reduced degradation rate and consequently a slower release of nutrients for microorganisms in the rumen. Whole vs deproteinized juice increased digestibility of cob DM (P = .11) and cell walls (P = .13), suggesting a response to level of degradable alpha-amino N. Whole and deproteinized juice increased cell wall digestibility compared with the negative control by 23.0 and 18.5 percentage units, respectively, suggesting that degradable alpha amino-N and cell solubles or other nutrients interacted to maximize microbial fiber digestion. Total and branch-chain volatile fatty acids measured at 6, 12 and 18 h post-feeding were highly correlated with nutrient digestibility. Ruminal NH3-N measured at 18 h was negatively correlated with dry matter (r = -.74) and cell wall (r = -.72) digestibility, showing that alfalfa supplies nutrients required by ruminal microorganisms for NH3 assimilation and fiber digestion. The mode of alfalfa associative action in high fiber diets is in supplying ruminal microorganisms with degradable protein and (or) other nutrients, rather than altering ruminal retention time.
在一项消化试验中，使用48只体重32千克的羔羊，研究了机械分离的苜蓿组分对采食量、消化率和瘤胃通过率的影响。将全株初花期苜蓿（粗蛋白含量25%）或其组分（压榨饼、脱水压榨饼、蛋白质凝块、脱水蛋白质凝块、全汁或脱蛋白汁）添加到3%氨（NH₃）处理的玉米芯阴性对照日粮中，添加水平相当于20%全株苜蓿干物质（DM）；共8种处理，每种处理6只羔羊。与20%直接刈割的苜蓿相比，苜蓿纤维（压榨饼）或添加汁的日粮随意采食量更高（P<0.05）。随意采食日粮时，干物质采食量、干物质和细胞壁消化率以及通过率高度相关。在干物质采食量相同时，脱水压榨饼与湿压榨饼相比，干物质和细胞壁消化率提高（P<0.05）。蛋白质加热可能降低了降解速率，从而使瘤胃中微生物的养分释放变慢。全汁与脱蛋白汁相比，玉米芯干物质（P = 0.11）和细胞壁（P = 0.13）消化率提高，表明对可降解α-氨基氮水平有反应。全汁和脱蛋白汁与阴性对照相比，细胞壁消化率分别提高了23.0和18.5个百分点，表明可降解α-氨基氮与细胞可溶物或其他养分相互作用，使微生物纤维消化最大化。采食后6、12和18小时测得的总挥发性脂肪酸和支链挥发性脂肪酸与养分消化率高度相关。18小时测得的瘤胃NH₃-N与干物质（r = -0.74）和细胞壁（r = -0.72）消化率呈负相关，表明苜蓿为瘤胃微生物提供了氨同化和纤维消化所需的养分。苜蓿在高纤维日粮中的协同作用模式是为瘤胃微生物提供可降解蛋白质和（或）其他养分，而不是改变瘤胃停留时间。
