Increasing the Feeding Value of Rice Straw, 2017

 

 

Project Leader

Josh Davy, farm advisor, UC Cooperative Extension Glenn, Colusa, and Tehama counties

This project continues many years of research investigating the use of rice straw for livestock forage.

Two feeding trials tested methods of improving the feeding value of rice straw. The first trial in 2015 examined feeding of high moisture straw in yearling cattle and subsequent body weight gain. High moisture straw had some drawbacks, including the need to be baled directly behind a combine. It also proved to be difficult to manage after baling. Stacks of high moisture straw tended to sag and potentially fall over.

The following year, treatments were added to low moisture straw to potentially improve feed intake. Treatments included ammoniation, a lactic acid application prior to baling, and molasses applied prior to baling. Only the ammoniation treatment substantially increased intake and weight gain.

Treatments planned for 2017 included high moisture, high moisture with lactic acid, low moisture, and low moisture with ammonia. Straw was baled during the fall rice harvest near Williams. Dry straw moisture was 9% and wet straw moisture averaged 51%. Both dry straw treatments were flail chopped. The wet straw would not feed through the baler. Because of this unforeseen difficulty, the high moisture–lactic acid treatment was dropped from 2017 research.

Low moisture bales were removed from the field immediately after baling and wrapped in plastic. Separate stacks were wrapped for both treatments. The ammonia treated stack was left in place for 30 days so the ammonia could evenly distribute throughout the stack. Unfortunately, part of the stack caught fire a week after harvest. However, enough salvageable unburned straw was hauled to the UC Sierra Foothill Research and Extension Center 30 days after harvest for feed testing.

The cattle feeding portion of the trial began on November 13 and lasted 60 days. Cattle were weighed, hip height and widths measured at the trial onset, midpoint, and at the end of the trial. A grain mix was included as a supplement. The ration was balanced with the anticipation that average consumption of straw and supplement would translate into a pound of cattle weight gain per day. Consumption was measured daily.

Targeting specific moisture levels has proven challenging. In some years, the straw dried within hours. In 2017 it was very slow to dry. Moisture levels ranged from 40% to 70% in the high moisture straw.

The cattle in the ammonia treatment significantly outperformed the other groups, gaining 1.7 pounds/day. The cattle fed the dry rice straw gained an average 1.2 pounds/day. The cattle fed high moisture rice straw gained 0.2 pounds/day. The difference in gain is attributable to intake amounts. The cattle fed ammonia treated rice straw consumed about 12 pounds per head per day, compared to 9.5 pounds per head per day in the low moisture treatment. The high moisture treatment had the lowest consumption at close to 8 pounds per head per day.

Hip height was not significantly affected by any of the treatments, which was similar to findings in previous trials. However, there were significant differences in hip width measurements, with the ammonia treatment again significantly increasing width over the high moisture treatment. The low moisture treatment was more variable and did not differ from the other treatments.

The differences in intake and resulting weight gain among treatments is a reflection of varying protein content in forage. The ammoniated treatment had significantly higher protein than all other treatments. Energy levels were significantly lower in the high moisture treatment compared to the other two treatments. This difference may actually be due to the high moisture treatment not being flail chopped prior to harvest. The wet straw could not be chopped. Sample date did not significantly contribute to forage quality, meaning that forage quality in all treatments remained relatively stable across the feeding periods.

In addition to forage quality, it appears mold and yeast counts may have significantly affected palatability. Mold counts were much higher in the high moisture treatment. The lactic acid treatment that was not completed potentially could have addressed this issue. In all three samplings, mold counts in the high moisture treatment were at high levels. The ammoniated treatment nearly eliminated mold, while the mold count in the low moisture straw was in the low to medium range.

Ongoing support of this project by the Rice Research Board is greatly appreciated. Researchers also extend thanks to the Parker family for their help with logistics and baling. Developing low cost forage sources is crucial to beef cattle production in California.