|Defining Forage Variability
in Rice Straw-04
Project Leader and Principal UC Investigators
Glenn Nader,livestock farm advisor, UC Cooperative Extension Butte/Sutter/Yuba Counties
This project continues to develop the research information necessary to create a viable niche for utilizing rice straw as a forage supplement for livestock feed.
The low digestibility of rice straw has been the limiting factor to its use thus far. However, research by UC scientists has shown that processing or “maceration” of rice straw improves its digestibility.
A commercial field macerator was investigated in 2004. Rice was treated at harvest time (60 percent moisture). Straw was allowed to dry and then baled. Samples from the macerated treatment and a control were analyzed by wet chemistry and by biological analysis.
Forty heifers were divided into four groups with two receiving a diet of macerated rice straw and two groups receiving the unmacerated straw. Each group was fed a diet of 60 percent alfalfa and 40 percent rice straw. Heifer consumption was recorded daily. Weight gains, body scores and fecal samples were collected about every two weeks for three months. This data is currently being analyzed.
The fundamental characteristic of cattle rations — around which all other nutrients are affected — is energy content. The level of energy in a ration is the sum of its component feeds. This is frequently expressed as total digestible nutrients (TDN) or metabolizable energy (ME). Two key factors determine energy value of forage — fat content and digestibility of structural fiber. An equation has been developed that gives producers an idea of how much metabolizable energy can be derived from individual feedstuffs. Researchers are working on streamlining the equation to analyze ration components.
Another part of this work is looking into whether rice straw fed directly from the field prior to drying may improve digestibility and nutritive value compared to baled straw. Drying straw may deplete soluble sugars by aerobic fermentation. Faster drying may conserve sugars. Studies elsewhere in the United States suggest that maceration of grasses and legumes may increase drying rates, spurring development of commercial field-scale maceration machines that are used to lift, macerate and replace windrows of field forages. This technology has not been applied to rice straw in the United States but researchers are evaluating its impact to rice straw digestibility.
More information on feeding rice straw to cattle can be obtained from a free UC publication, Feeding Rice Straw to Cattle, located on the Web at.