REVIEW: Rice Milling Coproducts as Feedstuffs for Beef Cattle

ABSTRACT

The objective of this paper was to collectively present literature on the performance, intake, and digestibility of diets containing rice milling coproducts. Rice milling coproducts may be an economical alternative feedstuff in the south-central United States and California; however, limited studies have been published in peer-reviewed journals on the utilization of rice milling coproducts within the United States. Most published research about rice milling coproducts were conducted outside the United States and application of results within the United States may be difficult due to basal dietary differences. Performance between cattle supplemented with corn and rice bran or de-oiled rice bran have been variable. Part of this variability may be due to variation in the nutrient composition of the rice bran among studies and regional differences due to milling procedures and rice varieties. Variability in performance results of rice bran and de-oiled rice bran and limited research with forages and feedstuffs common to the United States warrants a further investigation into how rice milling coproducts can be effectively used in cattle diets in the United States.

Key words: beef cattle, de-oiled rice bran, rice bran

INTRODUCTION

In 2005, 10 million metric tons of rice was produced in the United States (NASS, 2006). The south-central region (Arkansas, Louisiana, Mississippi, Missouri, and Texas) accounted for more than 80% of the total rice production. Outside of this region, California is the only other major rice producing state. Rice is composed of 3 basic components: the hull, a brown bran layer, and the kernel. The kernel, bran, and hull represent approximately 70, 10, and 20% of the weight of rough rice (Zachary Nehus, Riceland, Inc., Stuttgart, AR; personal communication). Milling rough rice initially requires removing the hull, leaving brown rice. White rice is then produced by removing the bran layer. The bran layer normally contains 15% fat (NRC, 1996) on a DM basis, and rice industries may subject the bran to further processing to extract the oil from the bran, producing residual de-oiled rice bran.

Coproducts of the rice milling industry - hulls, rice bran, de-oiled rice bran, and rice mill feeds (a mixture of hulls and bran) - may be an economical alternative to grains within these regions of the United States. Broken white rice that does not meet quality assurance standards is another possible feedstuff available from the rice milling industry; however, this is generally marketed to brewing and pet food industries.

Despite the large production of rice and rice coproducts in the south-central United States, limited research is available on the nutritional value (intake and digestion characteristics) and performance of beef cattle fed rice milling coproducts (Forster et al., 1994; Sanson and Coombs, 2003) with feedstuffs or forages grown in the United States. Numerous studies with rice milling coproducts have been conducted outside the United States.

The objective of this paper is to review the currently available literature on rice milling coproducts as feedstuffs for beef cattle.

REVIEW AND DISCUSSION

Rough Rice

Interest in feeding rough rice most often occurs when the market value for harvested rice is low. Beck (unpublished data) compared the in situ digestibility of unprocessed and ground rough rice. The ground rough rice was 3 times more digestible within 24 h of ruminai incubation than the unprocessed rough rice (75.5 and 25.9% digested for the ground and unprocessed samples, respectively). Actual digestibility values would differ for whole rough rice as a result of mastication. Bullocks fed diets containing 83.8% unprocessed rough rice gained 0.48 kg/d less than those fed crushed rough rice (Moran, 1973). The limitation of feeding unprocessed rough rice is due to the poor digestibility and palatability of the hull. Early experiments (Craig and Marshall, 1904) reported cattle offered rice hulls as a roughage source would not consume as much as cattle offered cottonseed hulls. In addition, White et al. (1971) reported the addition of 5% rice hulls did not alter digestibility compared with an all concentrate diet; however, increasing the rice hulls to 20% reduced the digestibility of the diet by 9.5%.

Historical work with feeding rough rice in the United States was published in research bulletins in Texas (Craig and Marshall, 1906; Cruse, 1910), Missouri (Weaver and Moffett, 1937), and Louisiana (Snell et al., 1945). These early experiments were set up as multiple treatment comparisons, without the replication required to draw statistical inferences by today's standards. Unground rough rice fed to steers (446 kg) at 0.6% body weight (as-fed) was reported to pass through undigested, and also was attributed as the cause of scouring and bloat problems (Cruse, 1910). Weaver and Moffett (1937) reported calves fed a 70% ground rough rice diet gained 15% less than calves fed a 75% whole shelled corn diet. In addition, the rough rice group required 24% more feed per unit of additional BW gain compared with the whole shelled corn group. Snell et al. (1945) reported that replacing corn with ground rough rice or rice polishings in finishing steer diets resulted in an 8 to 9% reduction in ADG and a 13% increase in the amount of feed required per unit of BW gain.

White (1966) reported that the crude fiber in diets containing 40% rice hulls had a …