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Effects of Xylanase on Concentration of Digestible and Metabolisable Energy in Rice Co-products Fed to Weaning Pigs

18 March 2015

Hans H Stein Monogastric Nutrition Laboratory

Several co-products from rice processing can be used as feed for pigs weighing around 14kg. The addition of a feed enzyme increased the energy content of some of the rice products tested.

Brown rice is the whole rice grain that is left after the hull layer has been removed, leaving the germ, starchy endosperm and bran.

Rice bran is the outer brown layer of brown rice, which is removed to produce white rice. It is high in fibre, and also contains about 15 per cent crude protein and 14 to 20 per cent fat.

Rice bran can be fed as full fat rice bran or defatted rice bran. Broken rice, or brewer's rice, consists of white rice grains that have been damaged in processing. It is high in starch and contains little fat, fibre or protein (Table 1).

Non-starch polysaccharides (NSPs), primarily arabinoxylan and cellulose, comprise 20 to 25 per cent of defatted rice bran. NSPs reduce nutrient absorption and energy digestibility.

Addition of exogenous xylanase to wheat co-products, which also have high concentration of NSPs, may improve digestibility of energy, but there is limited information about the effects of adding exogenous xylanases to rice co-products.

Therefore, an experiment was conducted to determine the effect on concentrations of digestible energy (DE) and metabolisable energy (ME) of adding exogenous xylanase to diets containing full fat rice bran (FFRB), defatted rice bran (DFRB), brown rice or broken rice.

Table 1. Analysed nutrient composition of brown rice, broken rice, full fat rice bran (FFRB) and defatted rice bran (DFRB)
Item per cent
Brown Rice Broken Rice FFRB DFRB
GE, kcal/kg 3,841 4,399 5,044 4,348
DM per cent 88.10 88.13 92.20 90.96
CP per cent 9.51 7.67 15.31 17.08
AEE per cent 3.15 1.42 19.28 1.11
Ash per cent 1.22 1.25 8.04 11.97
Starch per cent 66.80 76.83 29.58 28.30
ADF per cent 1.37 0.46 9.09 11.98
NDF per cent 2.66 0.61 14.13 19.27
Hemicellulose per cent 1.29 0.15 5.04 7.29

Materials and Methods

A total of 80 weanling barrows with an average initial bodyweight of 13.6kg were fed one of 10 diets.

The basal diet was based on corn and soybean meal.

Four experimental diets were formulated by including FFRB, DFRB, brown rice or broken rice in the diets at 50 per cent, while adjusting the corn and soybean meal so that the ratio remained constant.

Corn, soybean meal and rice co-products were the only sources of energy in the diets. Five additional diets that were identical to the initial five diets with the exception that they also contained 16,000 units of xylanase were also formulated.

Faeces and urine were collected and analysed to determine digestibility of gross energy and concentrations of DE and ME in the diets.

The difference procedure was used to calculate energy digestibility in ingredients.

Adding Xylanase Increases DE and ME of Rice Bran

In the diets that did not contain xylanase, DE and ME were greatest (P<0.05) in brown rice and in broken rice (Table 2).

FFRB contained less DE and ME than broken rice on a dry matter basis, but DE and ME was not different from values in brown rice. DFRB contained less DE and ME than all other ingredients.

Adding xylanase to the diets did not result in an increase in DE or ME in brown rice or broken rice.

However, addition of xylanase increased DE and ME in FFRB, resulting in DE and ME concentrations equal to or greater than in brown rice and broken rice. Adding xylanase increased the DE of DFRB on an as-fed basis, and the ME of DFRB on a dry matter basis but DFRB still had the least DE and ME of all ingredients.

Table 2. Concentration of DE and ME in brown rice, broken rice, full fat rice bran (FFRB) and defatted rice bran (DFRB) without or with xylanase
  Without xylanase With xylanase   P-Value
Item Brown rice Broken rice FFRB DFRB Brown rice Broken rice FFRB DFRB SEM Ingredient Xylanase Ingredient x xylanase
DE, kcal/kg 3,626c 3,696bc 3,824b 2,704e 3,632c 3,597c 4,137a 2,898d 72.02 <0.001 0.016 0.008
DE, kcal/kg of DM 4,120bc 4,183ab 3,984c 3,054d 4,127ab 4,087bc 4,311a 3,192d 78.84 <0.001 0.038 0.007
ME, kcal/kg 3,568bc 3,628bc 3,702b 2,743d 3,561bc 3,516c 4,029a 2,832d 64.87 <0.001 0.1 0.006
ME, kcal/kg of DM 4,055ab 4,124a 3,856b 2,936d 4,047ab 3,995ab 4,198a 3,225c 81.87 <0.001 0.0321 0.01

a-eMeans within a column lacking a common superscript letter are different (P<0.05).

Key Points

Addition of microbial xylanase to diets containing full fat and defatted rice bran, which contain relatively high concentrations of NSPs, increased DE and ME. Addition of xylanase to diets containing brown rice or broken rice did not increase DE and ME.

Brown rice and broken rice had the greatest concentrations of DE and ME in the diets without added xylanase. When microbial xylanase was added to the diets, DE and ME in full fat rice bran were the same as or greater than in brown rice and broken rice.

DFRB contained less DE and ME than brown rice and broken rice even if xylanase was included in the diets.

This report is based on unpublished research by Gloria Casas and Hans H. Stein.

March 2015

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