This project is researching ways to manipulate and manage rice straw to improve its value as a forage supplement in livestock feed. Research in 2007 focused on “double chop” rice straw in dairy heifer rations and studies of how field drying affects the nutritional quality of rice straw.

“Double chop” rice straw

In an effort to improve the consistency of rice straw used as a feed supplement for dairy cattle, researchers examined the effects of a special baler designed by Hesston that slices rice straw as it is baled; hence the name “double chop.” The objectives of this work were (1) to see how this technique affected mixing time and completeness of mixing in vertical and horizontal mixers typical of those used for feed preparation in Central Valley dairies and (2) to observe the impact of ration sorting and feeding behavior by the cows.

Dairy nutritional consultants helped identify five dairy producers who would participate in the study. Each dairy producer was given one 22-23-ton load of double-chop, forage-quality rice hay to feed to replacement heifers. No instructions on how to use the straw were given and each operation designed its own ration. Researchers toured each dairy and surveyed both the dairy manager and nutritionist about their experiences.

Producers found that double-chop rice straw broke up easily when bales were opened. In the previous year of this study, bales needed to be broken apart with a loader bucket prior to mixing. Dairies reported no difficulty mixing double-chop rice straw in either vertical or horizontal mixers. There was low sorting by cows and most ate the rations as mixed all day.

Most of the dairies used the rice straw as a bulk roughage component to the diet, providing heifers with rumen fill and stimulation. One dairy used it to replace alfalfa – as heifers were gaining too fast – at a dramatic savings in feed costs. The five dairies indicated a preference for this product (when properly baled for ease of mixing) over wheat straw. The rice grower cooperating in this demonstration project expanded his rice straw market to dairies by 5,500 tons.

With greater exposure to the technique, as well as extended drought and tight forage conditions, use of double-chop rice straw by dairy producers could increase significantly. California is a large market with nearly one million dairy replacement heifers in the state.

Field drying and quality

Previous attempts to improve rice hay forage quality through physical manipulation (i.e. maceration, flail chopping, rotary harvesting) were not successful. Thus research on factors affecting rice forage hay nutritional quality is now examining chemical changes occurring during field dry down and possible interventions to mitigate forage quality loss. Rice forage samples were collected from varieties M-401 and M-202 starting two weeks before harvest. Samples were analyzed for gas production with a rumen fluid method to determine impacts to digestibility.

During preharvest periods, the values for rice straw were near that of low-quality alfalfa. But at the end of a 48-hour, post-harvest drying period to simulate windrow conditions, dried rice straw dropped to a very low-quality forage. A small amount of additional forage quality loss occurred from days five through 33 after harvest. In all cases M-202 straw provided better digestibility than M-401 straw.

The project leader is working with the USDA Agricultural Research Service in Albany to study changes in the chemical properties of rice hay that may affect digestibility during field drying. One observation in harvested samples was a dramatic decline in moisture content from 55.5% at harvest to 10-15% within 48 hours. Future research will examine changes in cellulose and silica during the 48-hour drying period.

Publications in development

A University of California publication is being developed on producing rice straw for beef and dairy cattle forage. These end uses require different processes, as beef cattle operators are interested in high-moisture straw that has some green color, a forage quality test, and stays together in a bale when fed out on rangeland. In contrast, dairy producers want rice straw to mix well into a total ration for consistent nutrition, which requires chopping before baling at low moisture. The publication also covers other uses for rice straw (erosion control, housing).

The project leader is also preparing an article on the successful feeding of double-chop rice straw for California Dairy magazine and a peer-reviewed research article on physical manipulation of rice straw for the journal Animal Feed Science and Technology.