This project continues research on ways to utilize rice straw as a forage supplement in livestock rations. The focus of 2008 investigations was to improve rice straw utilization in dairy heifer rations and to educate dairy farmers about this alternative feed supplement through on-farm demonstrations.

Dairies like rice hay

The high cost of forages makes rice straw an attractive alternative for use in feed rations for dairy heifers. Rice straw provides an economical roughage source that can provide bulk in the diet and stimulate rumen development in heifers.

Five dairy nutritional consultants working in the southern San Joaquin Valley, and one in the Sonoma area, worked with dairy farmers to demonstrate how rice straw could be successfully incorporated in heifer total mixed rations (TMR).

Each consultant identified a dairy producer willing to experiment with rice straw. Each of those dairies was provided with a truckload (23 to 25 tons) of sliced, forage-quality rice straw. No instructions on how to use the straw were given, and each operation designed its own TMR.

The dairy manager and nutritionist at each location were surveyed at the conclusion of the demonstration.  The ration containing rice straw was fed, depending on the number of replacement heifers on the dairy, from four to eight weeks.  Most responses were very positive and virtually all the participants said they would be inclined to buy rice straw.

Baling quality effects

This part of the research project investigated how baling conditions affect rice straw structure, length and, consequently, how much rice straw can be mixed into TMR.

 Based on research from the previous year, modifications to field equipment were made to optimize mixability of the rice straw (and thus its marketability). A consistent supply of finely sliced rice straw with a fiber length of less than four inches is preferable. Harvest moisture above 13 percent increases fiber length in the bale slicer process. Lower moistures of 8-11 percent produced finer slicing and faster baling.

Fine-sliced rice straw improves mixing and sorting and allows feeding up to five pounds of rice straw per head per day without problems with the mixing equipment, or preferential sorting of feed by heifers.

Optimizing harvest quality

This research also examined how rice straw quality is affected by post-harvest conditions. Previous research showed forage quality dramatically declines from harvest to 48 hours after harvest.

In 2008, research compared frozen samples and dried rice straw for changes in cellulose and silica during this crucial drying period. A preliminary examination of silica levels showed higher amounts in M-401 than in M-202.  It was also found that freezing the samples at the time of harvest for later analysis does not accurately represent the nutritional quality of fresh rice straw.  Therefore, fresh straw cannot be frozen to simplify the experimental process.

In another study conducted with the help of UC Davis emeritus professors Emanuel Epstein and Bill Rains, 12 rice plants were harvested and analyzed at the boot stage. Preliminary results show that varying amounts of silica in growth media affect silica levels in plants and ultimately carbohydrate structure.  Additional research is under way to find optimal silica levels in growth media.

Samples from 53 rice straw stacks throughout Northern California were collected. Samples are being analyzed for neutral (NDF) and acid detergent fibers (ADF), lignin and cutin, silica, and crude protein content and compared to in vitro digestibility (digestion by cow rumen fluid) results.   Variability in crude protein levels may be related to varying amounts of nitrogen fertilizer applications.  The relationship of rice straw fiber content to digestibility is being studied.

Rice straw forage quality may also be affected by the drying process. Samples of M-206 rice plants were obtained from the Rice Experiment Station, grown to maturity and analyzed using a variety of laboratory techniques, including electron microscopy, for analysis of changes to cellulose and silica in the cell wall during drying. The testing and results from this comprehensive study will be completed in 2009.

Dairy industry education

Information for dairy operators was published through a number of trade journals, such as California Dairy, Ag Alert, Dairy Herd Management, and through conference posters and UC farm advisor newsletters.

An educational meeting for rice growers on preparing rice straw for dairy markets was held in Colusa in March 2008.

In November 2008, the project leader organized a tour for rice growers of a Sonoma County dairy that was feeding rice straw to dairy heifers. Growers got a first-hand understanding of what it takes for rice straw to work in dairy heifer TMR.