Stabilized rice bran shows promise as a feed ingredient for weaned pigs

Friday, June 7, 2013

Research suggests that supplementation of nursery diets with 10 per cent SRB matched feed efficiency of conventional diets supplemented with growth-promoting antibiotics

by JANICE MURPHY

According to the U.S. Department of Agriculture's National Agricultural Statistics Service, 11 million metric tons of rice were produced in the United States in 2010. Rice bran is a byproduct of rice milling, produced when the outer brown layer of bran is removed from the kernel to yield white rice. Under normal milling conditions, endogenous lipases are activated, causing rapid hydrolysis and rancidification of the oil within the bran.

However, a recently developed stabilization process has proven effective in deactivating the lipase enzyme and increasing shelf life up to one year. With the introduction of this new process, there is increased potential for stabilized rice bran (SRB) in the feed industry.

Although many components of SRB possess functional food properties, researchers at North Carolina State University (NCSU) recently focused their attention on the potential prebiotic characteristics of SRB non-starch polysaccharides in the intestines of newly weaned pigs.

Marcel Roberfroid, a researcher at Université Catholique de Louvain in Belgium, recently redefined the term prebiotic as "a selectively fermented ingredient that allows specific changes, both in the composition or activity in the gastrointestinal microbiota that confers benefits upon host well-being and health."

The nutrient composition of SRB suggests it has a potential use as a prebiotic in pig diets. Stabilized rice bran contains a large proportion of indigestible carbohydrate, with 20 to 25 per cent total fibre and two per cent soluble fibre. This fibre component can be used by intestinal bacteria for fermentation and may promote the colonization of a healthy intestinal microbial population.

With increasing grain prices and the pressure to remove antibiotics from pig diets because of concern over antibiotic resistance, the NCSU researchers set out to assess the interaction of SRB with dietary antibiotics in the diet of newly weaned pigs and their impact on growth performance and intestinal health.

Previous research findings failed to show improvements in growth performance with the inclusion of antibiotics in research settings, presumably because of higher standards for sanitation, husbandry and stocking density on research farms compared with commercial operations. To address this, the nursery rooms at NCSU were purposely not cleaned between weaning groups, with the goal of creating a more antibiotic-responsive environment.

Two hundred pigs, with an initial bodyweight of 6.27 kilograms, were weaned at 21 days of age and allotted to one of four dietary treatments (10 pens/treatment and five pigs per pen):
1) control diet (CON) with no antibiotics or SRB.
2) control diet plus antibiotics.
3) control diet plus 10 per cent SRB.
4) control diet plus antibiotics and 10 per cent SRB.

Diets were formulated to meet or exceed nutrient requirements for weaned pigs (National Research Council, 1998). The antibiotics used were a combination of chlortetracycline, sulfamethazine and penicillin. Diets were fed ad libitum over 28 days in two phases (Phase 1: Zero to 14 days post-weaning; Phase 2: 14 to 28 days post-weaning). Pig bodyweight and feed disappearance data were collected weekly. At the end of the trial, one pig from each pen was sacrificed to assess intestinal morphology.

Supplementing the control diet with antibiotics significantly improved average daily gain by 6.4 per cent during Phase 2, but other production variables remained unaffected (Table 1). During Phase 2 and throughout the entire 28-day experiment, supplementation with SRB improved gain:feed efficiency by 10 per cent in antibiotic-free pigs, but not in pigs fed antibiotics. Overall, across all diets, SRB improved the cumulative gain:feed ratio by four per cent.

The improvement in feed efficiency of pigs fed the antibiotic-free SRB diet may be a direct result of the prebiotic properties of SRB changing the intestinal environment, an idea that is supported by the results in the antibiotic treatment where the SRB supplementation failed to alter feed efficiency. The researchers speculated that SRB may have caused changes in food being digested and rate of passage, resulting in an alteration in transit time along the intestine. This would
affect the manner in which both nutrient absorption and microbial fermentation occurred in the weaned pigs.

Intestinal architecture is a key element in piglet health at weaning. Pigs fed the diet containing antibiotics plus SRB showed a significant increase in crypt depth by 50 micrometres (μm) (approximately 25 per cent) and a corresponding decrease in villi:crypt ratio from 3.23 to 2.62 (Table 2).

Although this ratio was decreased with feeding both antibiotics and SRB, there was no effect on intestinal enzyme activity and growth.

Compared to the adult pig, neonatal and weaned piglets are particularly sensitive to enteric infections. In adults, the microbial population is relatively stable, but it tends to be dynamic in the young pig, resulting in an increased risk of infection. With the exposure to new diets, environments and countless other variables, piglets weaned in a commercial operation experience many changes in their intestinal microbiota as they grow and mature.

Maintaining a balanced microbial environment with a large proportion of the beneficial bacteria, such as lactobacilli and bifidobacteria, in early development is generally believed to improve intestinal health. In this study, feeding SRB tended to increase bifidobacteria, but lactobacilli levels and intestinal concentrations of short chain fatty acids remained unaffected.

Based on the NCSU results, the researchers concluded that supplementation of nursery diets with 10 per cent SRB increased feed efficiency equivalent to that of conventional diets supplemented with growth-promoting antibiotics. This improvement in production and feed efficiency was accompanied by a trend towards increased levels of bifidobacteria, an indication that SRB does have prebiotic properties.

Stabilized rice bran shows promise as a feed ingredient for use in weaned pig diets, particularly in diets where there is a desire to remove antibiotics. Further research is necessary in commercial nursery environments to explore the efficacy of SRB as an alternative to antibiotic growth promoters. BP

Source: T. Herfel, S. Jacobi, X. Lin, E. van Heugten, V. Fellner and J. Odle. 2013. Stabilized rice bran improves weaning pig performance via a prebiotic mechanism. J. ANIM. SCI. Published online January 10, 2013. http://www.journalofanimalscience.org/content/early/2013/01/10/jas.2012-5287

Janice Murphy is a former Ontario agriculture ministry swine nutritionist who now lives and works in Prince Edward Island.