Double-low rapeseed meal (RSM) is currently used as a protein ingredient in animal diets. Heat treatment of RSM at varying processing conditions removes the residual hexane and efficiently reduces the glucosinolate content. However, variations in heat processing temperatures and duration of heat treatment may result in Maillard reactions, resulting in the formation of sugar-amino acid complexes. Maillard reaction products result in reduced standardized ileal digestibility (SID) of amino acids (AA), with Lys being the most sensitive AA. However, there is limited information about how heating affects the concentration of digestible energy (DE) and metabolizable energy (ME). Therefore, the objective of this experiment was to test the hypothesis that both the degree of heating and the time that heat is applied will affect the concentration of DE and ME and the SID of AA in double-low RSM fed to growing pigs.
Materials and Methods
Nine sources of RSM were used in the study. A conventional double-low RSM was either not autoclaved or autoclaved following one of 8 treatments: 110ºC for 15 or 30 min or 150ºC for 3, 6, 9, 12, 15, or 18 min. These 9 sources of RSM were used in 2 experiments.
Exp.1. Energy digestibility and concentrations of DE and ME
A corn-diet and 9 diets based on corn and each of the 9 sources of RSM were prepared. Thus, there were 10 diets in the experiment. Twenty growing barrows with an average initial BW of 21.23 ± 1.23 kg were randomly allotted to the 10 diets in a replicated 10 × 4 Youden Square with 10 diets and 4 periods. Thus, there were 2 pigs per diet in each period for a total of 8 replicate pigs per diet. Pigs were housed individually in metabolism crates that were equipped with a self-feeder, a nipple waterer, and a slatted floor. Urine and feces were collected for 5 d, and after determination of gross energy concentrations in diets, urine, and feces, concentrations of DE and ME in each source of RSM were calculated.
Exp. 2. Amino acid digestibility
Twenty growing barrows with an average initial BW of 69.81 ± 5.71 kg had a T-cannula installed in the distal ileum. Pigs were allotted to a replicated 10 × 4 Youden square design with 10 diets and four 7-day periods in each square. Pigs were placed in individual pens (1.2 by 1.5 m) that were equipped with a self-feeder, a nipple waterer, and a slatted tri-bar floor. The 10 diets included, a N-free diet and one diet containing each of the 9 sources of RSM as a sole source of AA, as described on Exp.1. Ileal digesta were collected on d 6 and 7 of each 7-d period. At the conclusion of the experiment, all sources of RSM, all diets, and all ileal digesta samples were analyzed for AA and values for the SID of AA in each source of RSM were calculated.
Results
Exp.1. Energy digestibility and concentrations of DE and ME
There were no differences for ATTD of DM and GE, DE, and ME, and DE and ME on a DM basis between the conventional RSM and RSM autoclaved at 110ºC (Table 1). However, there was a decrease (quadratic, P < 0.05) in ATTD of DM and GE, and concentrations of DE, and ME in RSM if RSM was autoclaved at150ºC.
Exp. 2. Amino acid digestibility
The SID of CP and all AA was less (P < 0.01) if RSM was autoclaved at 150ºC than at 110ºC, but there was no differences between RSM without heat treatment and RSM that was heat treated at 110ºC (Table 2). The SID of CP and all AA decreased (quadratic, P < 0.01) as the duration of heat treatment increased at 150ºC.
Key points
- Autoclaving of RSM at 110ºC for 15 or 30 min does not affect the ATTD of GE, DE and ME.
- Digestibility of AA, and DE and ME, are reduced if RSM is autoclaved at 150ºC and the longer the duration of autoclaving is the more the SID of AA and DE and ME are reduced.
- These results indicate that if crushing plants can avoid heating RSM to more than 110ºC during processing, the risk of over-heating is limited.
Table 1 Apparent total tract digestibility (ATTD) of GE, DM, and concentration of DE and ME in corn and rapeseed meal heat treated1, as-fed basis, Exp. 1
|
Item |
Corn |
RSM2 |
Heat treatment temperature |
Contrast P-value |
||||||||||||
|
110°С |
150°С |
RSM vs. 110°С |
110°С vs. 150°С |
At 110°С |
At 150°С |
|||||||||||
|
Duration (min): |
15 |
30 |
3 |
6 |
9 |
12 |
15 |
18 |
SEM |
Linear |
Linear |
Quadra tic |
||||
|
ATTD of GE, % |
92.2 |
75.6 |
77.1 |
75.5 |
69.0 |
72.7 |
63.7 |
65.1 |
65.2 |
62.6 |
2.51 |
0.82 |
<0.001 |
0.65 |
0.93 |
0.001 |
|
ATTD of DM, % |
93.5 |
73.3 |
75.8 |
73.7 |
67.8 |
71.2 |
63.1 |
64.1 |
64.6 |
62.1 |
2.31 |
0.60 |
<0.001 |
0.42 |
0.98 |
0.001 |
|
DE, kcal/kg |
3,530 |
3,161 |
3,239 |
3,220 |
2,919 |
3,147 |
2,731 |
2,788 |
2,793 |
2,737 |
104 |
0.58 |
<0.001 |
0.57 |
0.95 |
0.004 |
|
ME, kcal/kg |
3,457 |
2,873 |
3,013 |
3,017 |
2,720 |
2,936 |
2,508 |
2,619 |
2,547 |
2,458 |
114 |
0.28 |
<0.001 |
0.34 |
0.41 |
0.02 |
|
DE, kcal/kg DM |
4,000 |
3,425 |
3,506 |
3,784 |
3,171 |
3,410 |
2,960 |
3,023 |
3,016 |
2,967 |
113 |
0.60 |
<0.001 |
0.59 |
0.90 |
0.003 |
|
ME, kcal/kg DM |
3,918 |
3,113 |
3,262 |
3,264 |
2,955 |
3,182 |
2,719 |
2,839 |
2,750 |
2,665 |
123 |
0.30 |
<0.001 |
0.35 |
0.38 |
0.01 |
1Data are least squares means of 8 observations per treatment.
2RSM = rapeseed meal not autoclaved.
Table 2. Standardized ileal digestibility (%) of CP and AA in rapeseed meal (RSM) heat treated1,2, Exp. 2
|
Item |
Control3 |
Heat treatment temperature |
Contrast P-value |
||||||||||||
|
110°С |
150°С |
Control vs. 110°С |
110 °С vs. 150°С |
110°С |
150 °С |
||||||||||
|
Duration (min): |
15 |
30 |
3 |
6 |
9 |
12 |
15 |
18 |
SEM |
Linear |
Linear |
Quadra tic |
|||
|
CP |
73.4 |
71.6 |
73.9 |
64.2 |
56.5 |
44.4 |
46.3 |
44.2 |
28.7 |
2.34 |
0.820 |
<0.001 |
0.580 |
0.023 |
<0.001 |
|
Indispensable AA |
|||||||||||||||
|
Arg |
87.9 |
87.2 |
88.1 |
83.0 |
77.1 |
65.6 |
69.5 |
64.9 |
51.6 |
2.45 |
0.925 |
<0.001 |
0.811 |
0.001 |
<0.001 |
|
His |
84.3 |
82.5 |
83.8 |
79.0 |
74.9 |
66.1 |
67.2 |
65.7 |
54.8 |
1.47 |
0.476 |
<0.001 |
0.327 |
0.001 |
<0.001 |
|
Ile |
73.8 |
73.1 |
73.4 |
65.5 |
60.1 |
51.9 |
52.9 |
51.7 |
35.1 |
1.43 |
0.750 |
<0.001 |
0.741 |
0.002 |
<0.001 |
|
Leu |
78.2 |
77.4 |
77.4 |
69.7 |
66.0 |
59.3 |
60.6 |
59.4 |
45.5 |
1.29 |
0.600 |
<0.001 |
0.654 |
0.025 |
<0.001 |
|
Lys |
76.8 |
70.8 |
73.3 |
59.9 |
45.7 |
25.7 |
25.8 |
21.6 |
-0.49 |
2.69 |
0.095 |
<0.001 |
0.070 |
0.001 |
<0.001 |
|
Met |
50.3 |
44.7 |
50.3 |
36.5 |
23.3 |
10.5 |
9.4 |
9.5 |
-22.1 |
3.85 |
0.546 |
<0.001 |
0.293 |
0.012 |
<0.001 |
|
Phe |
76.6 |
76.2 |
76.2 |
68.7 |
66.2 |
61.2 |
62.0 |
60.5 |
50.1 |
1.73 |
0.840 |
<0.001 |
0.861 |
0.218 |
<0.001 |
|
Thr |
69.9 |
66.2 |
69.1 |
59.6 |
54.9 |
46.6 |
47.9 |
47.0 |
30.1 |
2.09 |
0.336 |
<0.001 |
0.181 |
0.096 |
<0.001 |
|
Trp |
72.1 |
69.6 |
71.6 |
63.7 |
61.0 |
55.7 |
56.7 |
58.1 |
44.4 |
1.77 |
0.506 |
<0.001 |
0.332 |
0.521 |
<0.001 |
|
Val |
73.3 |
70.6 |
72.9 |
65.7 |
60.4 |
52.2 |
52.9 |
51.6 |
36.6 |
1.87 |
0.489 |
<0.001 |
0.293 |
0.008 |
<0.001 |
|
Dispensable AA |
|||||||||||||||
|
Ala |
74.3 |
73.1 |
73.7 |
64.9 |
58.3 |
48.0 |
51.2 |
48.0 |
32.9 |
2.09 |
0.689 |
<0.001 |
0.651 |
0.028 |
<0.001 |
|
Asp |
72.3 |
68.4 |
69.4 |
54.9 |
43.7 |
32.4 |
35.0 |
33.6 |
12.2 |
2.88 |
0.274 |
<0.001 |
0.280 |
0.476 |
<0.001 |
|
Cys |
74.2 |
70.7 |
72.7 |
58.0 |
48.5 |
33.4 |
34.2 |
31.4 |
7.8 |
2.68 |
0.418 |
<0.001 |
0.332 |
0.015 |
<0.001 |
|
Glu |
84.7 |
83.5 |
84.9 |
78.9 |
74.2 |
65.7 |
67.6 |
65.5 |
54.4 |
1.45 |
0.714 |
<0.001 |
0.485 |
0.002 |
<0.001 |
|
Gly |
76.8 |
79.5 |
74.4 |
65.6 |
55.9 |
42.3 |
46.5 |
44.5 |
25.5 |
4.34 |
0.985 |
<0.001 |
0.654 |
0.241 |
<0.001 |
|
Pro |
97.4 |
98.0 |
96.8 |
82.4 |
67.9 |
34.1 |
55.7 |
35.1 |
36.9 |
11.03 |
0.999 |
<0.001 |
0.964 |
0.754 |
<0.001 |
|
Ser |
72.3 |
69.1 |
71.0 |
61.8 |
57.2 |
48.5 |
50.6 |
49.1 |
34.3 |
2.01 |
0.324 |
<0.001 |
0.227 |
0.186 |
<0.001 |
1Data are least squares means of 8 observations per treatment.
2Values for standardized ileal digestibility were calculated by correcting apparent ileal digestibility values for basal endogenous losses. Basal endogenous losses were determine using pigs fed the N-free diet as (g/kg DMI): CP, 16.09; Arg, 0.47; His, 0.15 Ile, 0.28; Leu, 0.45; Lys, 0.36; Met, 0.29; Phe, 0.25; Thr, 0.54; Trp, 0.14; Val 0.41; Ala, 0.60; Asp, 0.76; Cys, 0.21; Glu, 0.94; Gly, 1.50; Pro, 4.50; and Ser, 0.53.
3Rapeseed meal not autoclaved.