Hoffman P C, Combs D K, Casler M D
Department of Dairy Science, University of Wisconsin, Madison 53706, USA.
J Dairy Sci. 1998 Jan;81(1):162-8. doi: 10.3168/jds.S0022-0302(98)75563-8.
The nutrient contents of perennial ryegrass (Lolium perenne L.) and alfalfa (Medicago sativa L.) are reasonably similar. Despite similarities, the lactation performance of dairy cows fed perennial ryegrass has not been compared with the lactation performance of dairy cows fed alfalfa. The present study was implemented to compare the performance of lactating cows fed alfalfa or perennial ryegrass silage. Alfalfa and perennial ryegrass were harvested at late bud and boot stages of maturity, respectively, and ensiled in separate 4.9- x 18.3-m concrete silos. The experimental silages were supplemented with a concentrate mix at 31.1% of dietary dry matter and fed to 18 multiparous Holstein cows in early lactation in a crossover experimental design with 28-d periods. Digestibility and rate of passage of experimental diets were also measured using rare earth markers. The perennial ryegrass contained 3.0 percentage units more neutral detergent fiber than did alfalfa, but in vitro digestibility of neutral detergent fiber was 8.8 percentage units higher for perennial ryegrass. In vitro digestibility of dry matter was also higher for perennial ryegrass. Cows fed alfalfa silage produced more milk (31.8 kg/d) than did cows fed perennial ryegrass silage (30.2 kg/d). Cows fed perennial ryegrass silage ate less feed (2.2 kg/d) than did cows fed alfalfa. Because dry matter intake was lower, diet digestibilities were higher, and rate of passage was slower, for cows consuming perennial ryegrass. Based on laboratory evaluations, perennial ryegrass silage has high nutritional quality, but performance of lactating cows indicated that the forage was suboptimal for supporting high milk production when compared with alfalfa. The perennial ryegrass silage was suboptimal because it did not stimulate high amounts of dry matter intake in lactating cows.
多年生黑麦草（Lolium perenne L.）和苜蓿（Medicago sativa L.）的营养成分相当相似。尽管存在相似之处，但饲喂多年生黑麦草的奶牛泌乳性能与饲喂苜蓿的奶牛泌乳性能尚未进行比较。本研究旨在比较饲喂苜蓿或多年生黑麦草青贮饲料的泌乳奶牛的性能。苜蓿和多年生黑麦草分别在成熟的晚蕾期和孕穗期收获，并分别青贮于4.9×18.3米的混凝土青贮窖中。实验青贮饲料补充了占日粮干物质31.1%的精料混合料，并以交叉实验设计，在28天的周期内饲喂18头处于泌乳早期的经产荷斯坦奶牛。还使用稀土标记物测量了实验日粮的消化率和通过率。多年生黑麦草的中性洗涤纤维含量比苜蓿高3.0个百分点，但多年生黑麦草中性洗涤纤维的体外消化率高8.8个百分点。多年生黑麦草的干物质体外消化率也更高。饲喂苜蓿青贮饲料的奶牛产奶量（31.8千克/天）高于饲喂多年生黑麦草青贮饲料的奶牛（30.2千克/天）。饲喂多年生黑麦草青贮饲料的奶牛采食量（2.2千克/天）低于饲喂苜蓿的奶牛。由于采食多年生黑麦草的奶牛干物质摄入量较低，日粮消化率较高，且通过率较慢。基于实验室评估，多年生黑麦草青贮饲料具有较高的营养质量，但泌乳奶牛的性能表明，与苜蓿相比，这种牧草在支持高产奶量方面并非最佳选择。多年生黑麦草青贮饲料并非最佳选择，因为它不能刺激泌乳奶牛摄入大量干物质。
