Stefanon B, Pell A N, Schofield P
Dipartimento di Scienze della Produzione Animale, Università degli Studi di Udine, Italy.
J Anim Sci. 1996 May;74(5):1104-15. doi: 10.2527/1996.7451104x.
Alfalfa and bromegrass, each harvested at five different stages of maturity, were separated into water-insoluble and -soluble fractions. The NDF concentrations ranged from 19 to 43% for alfalfa and from 42 to 58% for brome. The rates of digestion, by mixed ruminal microflora, of the unfractionated forage and of the water-insoluble and -soluble fractions were measured in vitro using pressure sensors to monitor gas production. Both forages showed the expected decline in fiber digestibility with increasing maturity. A dual-pool logistic model gave pool sizes, specific rates, and a single lag time for both the faster- and slower-digesting fractions. The main difference between alfalfa and brome was in the soluble pool. This pool produced approximately 40% of the total gas in alfalfa, 25% in brome. The specific digestion rates of the brome soluble pool were approximately 50% higher than those for alfalfa. Net VFA production showed a somewhat higher acetate: propionate ratio for brome (3.2) compared with alfalfa (2.2), but there was little change with increasing maturity within a given forage. Gas production curves for the unfractionated forage showed a 0 to 10% positive deviation from curves created by adding data from separate digestion of the insoluble and soluble forage fractions. Gas measurements offer a promising approach to the study of the water-soluble extracts of forages and the interaction of the soluble- and insoluble-fractions during fermentation.
紫花苜蓿和雀麦草在五个不同成熟阶段进行收割，随后被分离成水不溶性部分和水溶性部分。紫花苜蓿的中性洗涤纤维（NDF）浓度范围为19%至43%，雀麦草的NDF浓度范围为42%至58%。使用压力传感器监测气体产生，在体外测定了未分级牧草以及水不溶性和水溶性部分被瘤胃混合微生物消化的速率。两种牧草均呈现出随着成熟度增加纤维消化率预期下降的趋势。一个双池逻辑模型给出了快速消化部分和慢速消化部分的池大小、特定速率以及单个滞后时间。紫花苜蓿和雀麦草之间的主要差异在于可溶性部分。该部分在紫花苜蓿中产生的气体约占总气体的40%，在雀麦草中占25%。雀麦草可溶性部分的特定消化速率比紫花苜蓿的约高50%。净挥发性脂肪酸（VFA）产生量显示，与紫花苜蓿（2.2）相比，雀麦草的乙酸与丙酸比例略高（3.2），但在给定牧草内随着成熟度增加变化不大。未分级牧草的气体产生曲线与通过将不溶性和可溶性牧草部分单独消化的数据相加得到的曲线相比，呈现出0%至10%的正偏差。气体测量为研究牧草的水溶性提取物以及发酵过程中可溶性部分和不溶性部分的相互作用提供了一种有前景的方法。
