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1、Chapter 4 Silage（青贮饲料）,4.1 Introduction,(1)Definition Silage is the material produced by the controlled fermentation of a crop of high moisture. Silage may be defined as fermented forage plants.,(2)History of silage It is a very old method of preserving feed. Columbus found that the Indians used pit
2、s or trenches in which to store their grain, and , centuries earlier in the Old World, silos were used as a means of preserving both grain and green forage. The first tower silo built in the USA by the white man is said to be erected by F. Morris in Maryland in 1876.,4.1 Introduction,(3)The reason o
3、f making silage Silage making is one of the 3 common methods of utilizing forage crops. Pasturing is the least expensive of the 3 methods, but it is seasonal in nature. Weather condition are not always favorable to haymaking. Ensiling can be done in inclement weather. Also, it has the added virtues
4、of succulence and of preserving a higher proportion of the nutrients of the plants than can be accomplished in haymaking.,4.1 Introduction,(4) Haylage (low-moisture silage，半干青贮) Haylage is made from grass or legume that is wilted to 40%-55% moisture content before ensiling. It is similar to silage e
5、xcept it is lower in moisture. Properly made haylage has a pleasant aroma and is a palatable, high-quality feed. Animals usually receive more DM and net feed value in haylage than in silage made from the same cut.,4.1 Introduction,(5)Kinds of crops used for silage Practically any crop may be made in
6、to silage, provided it contains : An appropriate level of moisture Adequate amounts of readily fermentable carbohydrates Adequate levels of other nutrients Provided it can be packed sufficiently Corn Most extensively used silage crop. Corn silage is unexcelled in quality.,4.1 Introduction, Forage so
7、rghum Most are very high yielding but do not produce the best silage. It inclined to contain excess water and acid, hence is not very palatable or nutritious. Grain sorghum Grain sorghum silage is between corn silage and forage sorghum silage in palatability. Higher DM content.,4.1 Introduction,4.2
8、The ensiling process,4.2.1 Aerobic activity The living plant cells of the forage continue to respire. The plant forage carries with it a large number of aerobic fungi and bacteria. The activity of aerobic microorganism gradually ceased with the development of anaerobic conditions. Aerobic yeasts and
9、 molds thrive and multiply.,4.2.2 Anaerobic activity Yeasts and molds die. Anaerobic bacteria, chiefly acid-forming and proteolytic（蛋白质分解的）, multiply at a prodigious(惊人的） rate. These bacteria, or enzymes produced by them, and enzymes from the cut plant material, attack the sugars and other material,
10、 breaking them into organic acids, principally lactic, acetic（乙酸） and formic（甲酸）, some ethyl alcohol(乙醇）, some gases like CO2, CH4, CO, NO, NO2.,4.2 The ensiling process,4.2.2 Anaerobic activity Much of sugars is changed to organic acids, and some of it is used for the bacteria and is built up into
11、compounds in their bodies. Small quantities of the proteins are broken down into ammonia, amino acid, amines（胺）, and amides（酰胺）.,4.2 The ensiling process,4.2.2 Anaerobic activity Some of the proteins are broken down into AA, but in badly preserved material the AA are broken further to various amines
12、 such as tryptamine（色胺 ）, putrescine（腐胺 ）, histidine（组氨酸） , phenylethylamine（苯基乙醇胺 ） etc., which at higher concentration may be harmful to the consuming animals. Yeasts, followed by molds, will again become active if silage is exposed to air.,4.2 The ensiling process,4.2.3 Optimum pH The acidity fin
13、ally reaches a point where the bacteria themselves are killed and the silage-making process is completed. The formation of a pH of 3.5-4.5 is the key to good wilted silage preservation. Excellent low-moisture silage (45-60% moisture) is frequently made in the pH of 4.0-4.5, and even up to 5.0.,4.2 T
14、he ensiling process,4.3 How to make good silage,Using a sound silo of proper size. Harvest at the proper stage of maturity Cut to proper length Control the moisture content An additive or preservative when needed Fill rapidly Distribute forage uniformly in the silo Seal or top-off the silo.,4.3.1 Ha
15、rvest at the proper stage of maturity The crop for silage making is generally harvested at the flowering stage when it has the maximum amount of nutrients. When cut at the proper stage of maturity, corn and sorghum forage possess just the right amount of sugar for the production of good silage. If c
16、ut when too immature, these crops, being high in sugar and water, may cause excessive acid formation and result in an unpalabable.,4.3 How to make good silage,4.3.1 Harvest at the proper stage of maturity Silage materials containing less than 25% DM (more than 75% moisture ) will form very sour silage. Plants for silage making may be allowed to mature till the DM content attains 35-40%.,4.3 How to make good silage,4.3.1 Harvest at the proper stage of maturity (1)“Black layer test” can
