Waghorn G C, Clark D A
Dexcel Limited, Private Bag 3221, Hamilton, New Zealand.
N Z Vet J. 2004 Dec;52(6):320-31. doi: 10.1080/00480169.2004.36448.
Perennial ryegrass is the primary forage component of ruminant diets in New Zealand. It is persistent and palatable, and immature ryegrass has a high nutritive value (NV). However, seedhead development substantially lowers its feeding value (FV) as fibre concentration increases, the rate and extent of digestibility decreases, and voluntary intake declines. Ryegrass pastures are susceptible to accumulation of endophytic and saprophytic fungi in dead material at the base of the sward, especially when mature and laxly grazed. Feeding forage legumes to ruminants grazing grass-dominant pastures will improve animal performance and lessen the reliance on a single species to meet all nutritional requirements. The FV of forage is a function of intake and NV, measured by chemical analyses and animal feeding trials. Performance of individual animals grazing forages is usually limited by energy intake because structural fibre can slow digestion and clearance from the rumen and because of competition between individuals for available feed. The use of metabolisable energy (ME) content of forage to signify FV can give a reasonable indication of animal performance, but it should be used in conjunction with chemical analyses to improve the accuracy of predictions. The relationship between FV, pasture production, animal performance and profitability is complex. The importance of skilled management to maintain pasture quality and optimise animal performance under inconsistent climatic conditions should not be underestimated. Acceptable animal performance with minimal veterinary intervention requires good nutrition, but the genetic potential of livestock in New Zealand cannot be met solely by grazing pasture, especially when a high utilisation of pasture is required to maintain quality and profitability. Producers are responding to industry demands to reduce the seasonality in supply of milk and meat by changing lambing and calving dates, and extending lactation length in dairy cows. Social changes include adoption of once-daily milking in the dairy industry. Some changes have necessitated increased use of supplements and others can be met by feeding forages with a higher FV than ryegrass, all of which require an improved knowledge of feed quality. This information is available through rapid and inexpensive near infrared spectroscopy (NIRS) analysis, enabling animal nutritional needs to be balanced by appropriate nutrient supply. It is essential that producers continue to improve animal welfare, limit excessive use of fertilisers and meet the demands of overseas consumers. Good nutrition, with an increased use of legumes and other forages to complement ryegrass pastures, will enable these objectives to be achieved.
多年生黑麦草是新西兰反刍动物日粮的主要饲料成分。它生长持久且适口性好，未成熟的黑麦草具有较高的营养价值（NV）。然而，随着抽穗期的到来，其饲用价值（FV）会大幅降低，因为纤维浓度增加，消化率的速率和程度降低，采食量也会下降。黑麦草牧场易在草皮基部的死草中积累内生真菌和腐生真菌，尤其是在成熟且放牧稀疏时。给以禾本科牧草为主的牧场放牧的反刍动物饲喂豆科牧草，将提高动物生产性能，并减少对单一物种来满足所有营养需求的依赖。饲料的饲用价值是采食量和营养价值的函数，可通过化学分析和动物饲养试验来衡量。采食牧草的个体动物的生产性能通常受能量摄入量限制，这是因为结构性纤维会减缓瘤胃中的消化和排空速度，还因为个体之间会争夺可用饲料。用饲料的代谢能（ME）含量来表示饲用价值，能够合理地反映动物生产性能，但应结合化学分析使用，以提高预测的准确性。饲用价值、牧场产量、动物生产性能和盈利能力之间的关系很复杂。在气候条件不稳定的情况下，熟练管理对于维持牧场质量和优化动物生产性能的重要性不可低估。在最少兽医干预的情况下实现可接受的动物生产性能需要良好的营养，但仅靠放牧牧草无法满足新西兰家畜的遗传潜力，尤其是在需要高利用率的牧场来维持质量和盈利能力时。生产者正在响应行业需求，通过改变产羔和产犊日期以及延长奶牛的泌乳期来减少牛奶和肉类供应的季节性。社会变革包括乳业采用每日一次挤奶。一些变革需要增加补充饲料的使用，其他变革则可以通过饲喂饲用价值高于黑麦草的牧草来满足，所有这些都需要提高对饲料质量的认识。通过快速且廉价的近红外光谱（NIRS）分析可获取此信息，从而通过适当的养分供应来平衡动物的营养需求。生产者必须继续改善动物福利，限制过度使用化肥，并满足海外消费者的需求。良好的营养，增加豆科牧草和其他牧草的使用以补充黑麦草牧场，将有助于实现这些目标。
