Commercial poultry feeds may contain insufficient fiber

Scientists looking for ways to release nutrients from rice bran conclude a review of commercial milling practices may be in order.

Boggy |

A study that set out to find new ways to incorporate low-cost ingredients into animal feed came away with an entirely different lesson: commercial poultry feed may not contain enough fiber.

Researchers from Canadian Bio-Systems Inc. and the Universities of Guelph and Manitoba hoped to identify an enzyme blend that would allow poultry to digest feed containing rice bran, a processing waste product that is widely available in rice-loving countries. The bran is extremely high in fiber — to the point of being largely indigestible. But the researchers figured that certain enzymes could break down the fiber in the bran, rendering it a useful and cost-effective feed ingredient.

But the study — a limited set of trials that corresponding author Elijah Kiarie said merits further investigations — found no evidence that the enzymes interacted with the rice bran to make it more digestible. However, by themselves, the enzymes and, under certain circumstances, the rice bran, promoted faster growth among bird that received one or the other.

Kiarie, an assistant professor of poultry nutrition at the University of Guelph, said the enzymes did what they were expected to do: They enabled the birds to make better use of the nutrients in their feed, even if they didn’t succeed at unlocking the rice bran nutrients. Including the enzyme blend, consisting of xylanase, β-glucanase, invertase, protease, cellulase, α-amylase and mannanase, improved poultry performance regardless of whether the birds were fed a corn-soy-rice bran blend, or a corn-soybean blend that did not include the bran.

However, birds fed a blend containing about 5% rice bran also grew faster than those on the traditional corn-soy feed — even if they did not receive the enzymes. Growth slowed when birds ate diets containing more than 10% rice bran, according to the study published in the journal Animal Nutrition.

The findings merit further investigation, Kiarie said, because it could suggest that commercial poultry feeds do not contain adequate fiber. The birds fed the 5% rice bran diet developed larger, healthier gizzards, which may have improved their digestion of other ingredients and accelerated growth.

Kiarie said he doesn’t believe the study supports adding rice bran to animal feed as a fiber supplement, but it may lead to research into how poultry feeds are milled. Current processes, he said, mill feed down to very fine particles, which may remove structure from the diet. Larger particles, he hypothesized, may improve gizzard health and performance.

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