Studies on the Improvement of the Nutritive Calue of Low Quality Roughage

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Recently, many researches have been conducted on improving the nutritive value of low quality roughage such as straw, which is a most abundant but little nutritious resources as ruminant feed, by physical, chemical and biological treatments. Low quality roughage usually has insufficient level of nitrogen and slowly degradable fiber, which limits its voluntary intake. An adequate nitrogen supplement increases the voluntary intake, improves N utilization in animals and sometimes improves fiber digestibility.While herbages in vegetative stage are very high in fiber digestibility but contain excess soluble nutrients for ruminants. This excess can be easily removed into Green Juices (GJ) by pressing them leaving as nutritious residue as material crop.GJ contains much protein and soluble components and consequently may serve as a good additive source for low nitrogen feeds. If it is alkalized before addition to straw, an improvement of fiber digestibility can also be expected.Rice straw silage added with GJ at ensiling as to make the moisture content to 70%, contained 3-4% more crude protein than those ensiled with water. Addition of NaOH treated GJ was not only effective on improving the digestibility of fibrous components but also on increasing nitrogen retention of animals by reducing ruminal ammonia concentration, plasma urea level and urinary N excretion. But the improved fiber digestibility by the NaOH addition was 10% lower than that obtained on the rice straw silage added with ammonia treated GJ. The reason of the difference between the two alkali-treated silages are still under investigation but may be attributable to the different N content between them.