The Loss of Nutrients in Hay and Meadow Crop Silage during Storage

Abstract

Summary Storing as hay. In well-cured hay or that containing less than 30 per cent moisture, the dry-matter loss in storage will vary from 3.5 to 9 per cent and in some cases more. This loss occurs principally in the nitrogen-free extract and to a lesser degree in the ether extract. Hay containing in excess of 30 per cent moisture is not considered safe for ordinary storage. In such cases, extensive heating results that may lead to either spontaneous combustion or to the production of charred, blackened or browned hay. Dry matter losses depend upon temperatures attained and their duration. In browned and blackened hay such losses may range from 15 to 40 per cent. Heating reduces the digestibility of the hays, especially of the proteins, and increases the carotene loss. Although some browned hays have been found palatable, in general, browned hay, and blackened hay especially, are less palatable than hays that have not heated. At a given moisture content chopped hay will heat more than hay. A long chop is preferable to a short chop. Such hay should contain less than 25 per cent moisture for storage. Salting hay will not prevent excessive heating in under-cured forage. For field baling, hay should contain less than 25 per cent moisture. The losses in dry matter and nutrients (carotene excepted) of artificially dried hay are practically negligible in storage. Mow-drying of hay by forced ventilation with or without artificial heat has been shown to result generally in hay of good quality with a high feeding value. In cases where fermentations and heating have occurred, it is logical to assume that losses will be encountered just as in ordinary storage. Much more work on the nutrient content, feeding values and palatability of mow-cured hay needs to be done. Losses in carotene take place in the storage of well-cured hay, in the mow, so that at the end of 300 days, such hays may have only one-quarter of their original value. In the heating of hay the carotene may be entirely lost. The losses are greater in warm weather than in cold weather. Storing as silage. The percentage loss from top spoilage will vary with the size of the silo and the precautions taken in sealing the silo. A loss of 3 to 6 per cent of the total dry matter of ensiled material is a general estimate. The actual weight of spoiled material removed from the top of a silo may represent a proportionally larger amount of original forage, because of the loss of organic matter through decay and the drying out of the material. The percentage losses through seepage also vary with the size of the silo and the moisture content of material ensiled. Normally the dry matter losses from this cause are less than 1 per cent, when the original forage contained 70 per cent or less moisture. Fermentation losses in dry matter will normally vary between 5 and 10 per cent. This is exclusive of losses from top spoilage or seepage. The feed analyses of silage is similar to the analyses of the material ensiled. The digestibility of the silage is likewise similar to the original green material, except in silage in which extensive heating has taken place. In such cases the digestibility of the protein is lowered. Carotene is generally well preserved in the ensiling process. According to some work the carotene retained in the silage averaged from 60 to 90 per cent of that ensiled. Other investigators show lower carotene retentions. Considerable variation exists in the amount of carotene retained in silage. The type of treatment has been shown to have an effect on carotene preservation. In general, treatment with mineral acids shows high retention and no treatment or wilting has given the lowest retention. The high carotene content of the silage is reflected in the carotene content of milk produced on such silage. The grass-juice factor has been shown to be present in grass silage, especially in silage preserved with soured whey or with phosphoric acid. The ensiling process destroys the germinating powers of a number of different weed seeds. Proper moisture evaluation and control are needed for minimizing the losses in storing forages as hay and silages.