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Amino Acid Digestibility in Rice Co-products Fed to Growing Pigs

01 January 2015

Hans H Stein Monogastric Nutrition Laboratory

A University of Illinois study has established the digestibility of the crude protein and amino acids in broken rice, two sources of full fat rice bran and defatted rice bran for growing pigs.

Global production of rice is third in terms of total tonnage after corn (maize) and wheat. Rice is grown to produce polished white rice for human consumption. However, harvested rice, called paddy rice or rough rice, needs to be dehulled, which results in production of brown rice.

The outer brown bran layer of brown rice, known as rice bran, also needs to be removed before polished white rice is produced.

Approximately 20 per cent of the paddy rice is hulls and the bran fraction is eight to 10 per cent, so only 70 per cent of the paddy rice will become polished rice. Rice bran 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. During milling of the rice, some kernels may get broken and cannot be used for human consumption. These broken kernels are known as broken rice or brewers rice and may also be used in animal feeding. Broken rice is high in starch and contains little fat, fibre or protein.

Thus, both rice bran and broken rice may be fed to pigs but these ingredients are poorly characterised in terms of nutritional value.

An experiment was, therefore, conducted at the Hans H. Stein Monogastric Nutrition Laboratory to determine the standardised ileal digestibility (SID) of crude protein and amino acids in broken rice, two sources of full fat rice bran (FFRB) and defatted rice bran (DFRB) fed to growing pigs.

Experimental Design

Seven growing pigs with an average initial body weight of 70.07kg were fed one of six diets. The control diet was based on bakery meal, which is a mixture of by-products from the bakery and confectionery industries.

Bakery meal was used because it is highly palatable to pigs. Four diets were formulated by mixing bakery meal with one of four rice co-products: broken rice, two sources of FFRB, and one source of DFRB.

A nitrogen-free diet that was used to determine endogenous losses of crude protein and amino acids was also formulated. Because none of the diets contained sufficient amino acids to meet the requirements for growing pigs, an amino acid mixture was fed to the pigs in the adaptation periods to the diets.

The apparent ileal digestibility of amino acids in the experimental ingredients was calculated using the difference procedure, and adjusted for endogenous losses to calculate standardised ileal digestibility.

Results

Table 1. Analysed nutrient composition (as-fed basis) of broken rice,
full fat rice bran (FFRB-1 and FFRB-2) and defatted rice bran (DFRB)
 Ingredient
ItemBroken riceFFRB-1FFRB-2DFRB
Gross energy, kcal/kg 4,399 4,554 5,044 4,348
Dry matter, % 88.13 95.11 96.20 90.96
Crude protein, % 7.67 14.30 15.31 17.08
AEE, % 0.85 17.06 19.28 1.09
Ash, % 1.25 8.69 8.04 11.97
Starch, % 76.83 25.58 29.58 28.30
Acid detergent fibre, % 0.46 9.42 9.09 11.98
Neutral detergent fibre, % 0.61 14.76 14.13 19.27
Lignin, % 0.35 3.01 3.51 4.32
Indispensable
amino acids, %:
Arg 0.52 1.11 0.61 1.21
His 0.16 0.38 0.76 0.42
Ile 0.29 0.47 0.27 0.59
Leu 0.59 0.94 3.22 1.18
Lys 0.28 0.65 0.55 0.79
Met 0.20 0.27 1.18 0.33
Phe 0.36 0.57 0.56 0.71
Thr 0.25 0.49 0.35 0.63
Trp 0.07 0.16 0.15 0.18
Val 0.40 0.72 0.79 0.91
Total 3.12 5.76 8.44 0.95
Dispensable
amino acids, %:
Ala 0.40 0.82 0.87 1.03
Asp 0.63 1.15 1.26 1.49
Cys 0.15 0.28 0.30 0.32
Glu 1.23 1.76 1.86 2.09
Gly 0.32 0.73 0.78 0.89
Pro 0.35 0.58 0.62 0.78
Ser 0.35 0.53 0.57 0.63
Tyr 0.16 0.35 0.40 0.47
Total 3.5 6.20 6.66 7.70
Lys:CP ratio, % 3.65 4.54 3.59 4.62

The SID of crude protein and all amino acids was greater (P<0.01) in broken rice than the rice bran products (Table 2).

Table 2. Standardised ileal digestibility (%) of CP and AA in broken rice,
two sources of full fat rice bran (FFRB-1 and FFRB-2) and defatted rice bran (DFRB)
 Ingredient  
ItemBroken riceFFRB-1FFRB-2DFRBSEMP-value
Crude protein, % 97.2 a 83.9 b 79.8 c 78.7 c 1.25 <0.0001
Indispensable
amino acids. %:
Arg 98.7 a 93.8 b 92.2 bc 90.5 c 0.81 <0.0001
His 95.1 a 88.6 b 87.0 c 82.7 d 0.67 <0.0001
Ile 93.2 a 83.5 b 82.9 b 78.4 c 1.01 <0.0001
Leu 94.1 a 83.0 b 82.2 b 77.7 c 0.95 <0.0001
Lys 94.5 a 88.5 b 83.1 c 82.3 c 1.02 <0.0001
Met 92.9 a 87.4 b 87.2 c 78.7 d 0.60 <0.0001
Phe 94.0 a 81.0 b 81.1 b 78.0 b 2.22 <0.0001
Thr 95.0 a 81.4 b 79.8 bc 77.0 c 1.41 <0.0001
Trp 94.3 a 84.6 b 81.4 bc 79.7 c 1.35 <0.0001
Val 94.2 a 84.2 b 83.6 b 79.0 c 0.97 <0.0001
Total 94.9 a 86.2 b 85.0 b 81.7 c 1.01 <0.0001
Dispensable
amino acids, %:
Ala 94.7 a 85.8 b 84.4 b 82.3 c 1.09 <0.0001
Asp 94.4 a 83.6 b 79.8 c 77.4 d 0.90 <0.0001
Cys 94.2 a 81.2 b 78.3 b 74.5 c 1.33 <0.0001
Glu 94.1 a 87.5 b 86.4 b 81.8 c 1.03 <0.0001
Gly 103.6 a 81.0 b 78.1 bc 78.0 b 3.40 <0.0001
Pro 185.5 a 127.0 b 126.1 b 134.7 b 19.01 <0.0001
Ser 96.3 a 83.0 b 81.3 b 77.9 c 1.06 <0.0001
Mean1 95.0 a 86.2 b 85.1 b 81.7 c 1.30 <0.0001
All amino acids 95.2 a 85.3 b 84.2 b 80.5 c 1.14 <0.0001
a-d Means within a row lacking a common letter are different (P<0.05).
1 Values for Pro were not included in the calculated mean for dispensable AA.

This is likely due to the lower concentration of fibre in broken rice. The SID of crude protein was greater (P<0.01) in FFRB-1 than in FFRB-2 but the average SID of indispensable amino acids and of all amino acids did not differ between the two sources of FFRB.

The SID of crude protein was the same in DFRB as in FFRB-2 but the mean SID of indispensable amino acids and of all amino acids was less (P<0.01) in DFRB than in the two sources of FFRB.

Although digestibility of amino acids was less in DFRB than in the other rice co-products, the relatively high concentration of crude protein and amino acids in DFRB (Table 1) meant that it had the greatest (P<0.001) concentration of standardized ileal digestible amino acids of the test ingredients (Table 3).

Table 3. Concentrations (g/kg DM) of standardised ileal digestible CP and AA in broken rice,
two sources of full fat rice bran (FFRB-1 and FFRB-2) and defatted rice bran (DFRB)
 Ingredient  
ItemBroken riceFFRB-1FFRB-2DFRBSEMP-value
Crude protein, % 84.6 c 126.1 b 127.1 b 148.3 a 2.22 <0.001
Indispensable
amino acids, g/kg DM:
Arg 5.8 d 10.0 c 11.3 b 12.1 a 0.10 <0.001
His 1.7 d 3.5 c 3.6 b 3.9 a 0.04 <0.001
Ile 3.1 d 4.1 c 4.4 b 5.2 a 0.63 <0.001
Leu 6.3 d 8.2 c 8.7 b 10.1 a 0.11 <0.001
Lys 3.0 d 6.0 b 5.5 c 7.2 a 0.83 <0.001
Met 2.1 c 2.5 b 2.5 b 2.9 a 0.04 <0.001
Phe 3.9 c 4.9 b 5.0 b 6.1 a 0.13 <0.001
Thr 2.7 c 4.2 b 4.4 b 5.4 a 0.09 <0.001
Trp 0.7 d 1.4 b 1.2 c 1.6 a 0.21 <0.001
Val 4.3 d 6.4 c 6.8 b 8.0 a 0.95 <0.001
Mean 33.6 c 52.2 b 53.3 b 62.7 a 0.70 <0.002
Dispensable amino acids, g/kd DM:
Ala 4.3 d 7.4 b 5.2 c 9.3 a 0.11 <0.001
Asp 6.7 c 10.1 b 10.3 b 12.8 a 0.14 <0.001
Cys 1.6 c 2.4 b 2.4 b 2.6 a 0.05 <0.001
Glu 13.1 c 16.2 b 16.3 b 18.8 a 0.25 <0.001
Gly 3.8 c 6.2 b 6.0 b 7.7 a 0.28 <0.001
Pro 7.4 b 7.7 b 7.6 b 12.1 a 1.07 <0.001
Ser 3.8 c 4.6 b 4.7 b 5.5 a 0.07 <0.001
Total 37.2 c 51.9 a 49.7 b 51.9 a 0.97 <0.001
All AA 70.8 c 104.2 b 103.2 b 126.1 a 1.65 <0.001
a-d Means within a row lacking a common letter are different (P<0.05).

The concentration of SID crude protein and amino acids was not different between FFRB-1 and FFRB-2. Broken rice, which has a low concentration of crude protein and amino acids, had the least (P<0.01) SID of crude protein and amino acids despite the high digestibility of amino acids in this product.

Key Points

The SID of crude protein and amino acids in broken rice was greater than in the rice bran products.

Due to its higher fat content, FFRB had greater digestibility of amino acids than DFRB.

Because of its relatively high protein content, the concentration of standardised ileal digestible crude protein and amino acids is greatest in DFRB.

Broken rice contains less SID crude protein and amino acids than any of the rice bran products.

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

January 2015

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