Sorghum is used as an alternative to corn due to its lower cost and wide availability. However, conventional sorghum contains high concentration of tannin and phytate, which act as antinutritional factors. Use of microbial phytase may hydrolyze phytate and subsequently improve P absorption. High-lysine sorghum is a new variety of sorghum which may be comparable to other cereal grains and may serve as alternative to corn for pigs. However, there are at this point no data for effects of adding phytase to diets containing sorghum and no data to demonstrate the nutritional value of high-lysine sorghum.
Therefore, 2 experiments were conducted to test the hypothesis that inclusion of 500 phytase units (FTU)/kg of microbial phytase improves the standardized total tract digestibility (STTD) of P in sorghum varieties. The second hypothesis was that the STTD of P, as well as concentrations of digestible energy (DE) and metabolizable energy (ME) in high-lysine sorghum is not different from that of corn and other sources of sorghum.
Experimental design
One source of high-lysine sorghum, one source of red sorghum, one source of white sorghum, and one source of yellow dent corn was ground to approximately 500 microns. The high-lysine sorghum, red sorghum, white sorghum, and yellow dent corn that were used in the 2 experiments originated from the same batches (Table 1).
Experiment 1: Phosphorus Digestibility
Forty eight barrows (18.63 ± 0.89 kg) were housed individually in metabolism crates and randomly allotted to 4 diets and 2 levels of microbial phytase (0 or 500 units/kg) in a randomized complete block design. There were 6 replicate pigs per diet. Diets were based on high-lysine sorghum, red sorghum, white sorghum, or corn as the sole source of P and these diets either contained no microbial phytase or 500 units/kg of phytase. Feces were collected using the marker to marker approach with 5-d adaptation and 4-d collection periods. Basal endogenous losses and STTD of P in experimental diets were calculated based on intake and fecal and urine output of P.
Experiment 2: Energy Measurements
Thirty two barrows (18.54 ± 0.77 kg) were housed individually in metabolism crates and randomly allotted to 1 of 4 diets. Each diet was fed to 8 pigs. Diets contained high-lysine sorghum, red sorghum, white sorghum, or corn as the only energy-containing ingredient. Feces and urine samples were collected using the marker to marker approach with 5-d adaptation and 4-d collection periods. Samples were analyzed for gross energy to calculate for the concentrations of DE and ME in each source of grains.
Results
Experiment 1: Phosphorus Digestibility
No differences in ATTD or STTD of P were observed among pigs fed the sorghum varieties or corn (Table 2). Addition of phytase to diets did not affect feed intake, daily fecal output, or daily P intake. However, pigs fed diets with phytase had less (P < 0.01) daily fecal P output and concentration of P in feces, which resulted to an improvement (P < 0.01) in P absorption, ATTD of P, and STTD of P. There was no effect of phytase addition on daily endogenous P loss.
Experiment 2: Energy Measurements
The ATTD of GE in high-lysine sorghum and red sorghum were less (P ≤ 0.01) than in white sorghum and corn (Table 3). The DE and ME on an as-fed basis in corn were not different from the DE and ME values obtained for all sorghum varieties. However, values for DE and ME in red sorghum on an as-fed basis were less (P < 0.05) than in other sorghum varieties. On a DM basis, values for DE and ME in red sorghum were less (P < 0.05) than in other sorghum varieties and in corn.
Key points
- The STTD of P in high-lysine sorghum was not different from values obtained for conventional varieties of sorghum and in corn.
- Addition of microbial phytase improved the STTD of P in all ingredients.
- The concentrations of DE and ME in high-lysine sorghum were not different from corn and other sources of sorghum.
Table 1. Analyzed nutrient composition of ingredients (as-fed basis)
|
Item |
High-lysine sorghum |
Red sorghum |
White sorghum |
Corn |
|
Dry matter, % |
89.31 |
87.59 |
87.41 |
85.65 |
|
GE1, kcal/kg |
3,959 |
3,827 |
3,794 |
3,740 |
|
CP1, % |
13.92 |
9.49 |
8.38 |
6.46 |
|
AEE1, % |
3.50 |
3.20 |
4.04 |
4.52 |
|
IDF2, % |
11.90 |
10.10 |
10.70 |
11.70 |
|
SDF2, % |
0.10 |
0.40 |
0.20 |
0.20 |
|
TDF2, % |
12.00 |
10.50 |
10.90 |
11.90 |
|
Ash, % |
1.66 |
1.72 |
1.33 |
1.18 |
|
Ca, % |
0.02 |
0.02 |
0.01 |
0.03 |
|
Total P, % |
0.35 |
0.32 |
0.30 |
0.26 |
|
Phytic acid, % |
0.97 |
0.88 |
0.81 |
0.69 |
|
Phytate bound P3, % |
0.27 |
0.25 |
0.23 |
0.19 |
|
Nonphytate P4, % |
0.08 |
0.07 |
0.07 |
0.07 |
|
Phytase, FTU5/kg |
<70 |
<70 |
<70 |
<70 |
|
Carbohydrates |
||||
|
Glucose, % |
0.34 |
0.40 |
0.39 |
0.44 |
|
Sucrose, % |
0.77 |
0.37 |
0.63 |
1.45 |
|
Maltose, % |
0.05 |
0.14 |
0.08 |
0.11 |
|
Fructose, % |
0.18 |
0.11 |
0.12 |
0.25 |
|
Stachyose, % |
0.06 |
ND6 |
ND |
ND |
|
Raffinose, % |
0.10 |
ND |
0.08 |
0.15 |
|
Starch, % |
57.74 |
62.40 |
62.46 |
59.12 |
|
Minerals |
||||
|
K, % |
0.39 |
0.28 |
0.33 |
0.32 |
|
Mg, % |
0.15 |
0.14 |
0.13 |
0.10 |
|
Na, mg/kg |
35.00 |
7.00 |
7.00 |
49.00 |
|
S, % |
0.14 |
0.10 |
0.09 |
0.11 |
|
Cl, % |
<0.10 |
<0.10 |
<0.10 |
<0.10 |
|
Cu, mg/kg |
5.00 |
2.00 |
2.00 |
2.00 |
|
Fe, mg/kg |
38.00 |
38.00 |
36.00 |
35.00 |
|
Mn, mg/kg |
15.00 |
14.00 |
16.00 |
8.00 |
|
Se, mg/kg |
<0.20 |
0.60 |
0.30 |
0.40 |
|
Zn, mg/kg |
26.00 |
20.00 |
20.00 |
21.00 |
1GE = gross energy; CP = crude protein; AEE = acid hydrolyzed ether extract.
2IDF = insoluble dietary fiber; SDF = soluble dietary fiber; TDF = total dietary fiber.
3Calculated as 28.2% of phytic acid.
4Calculated as total P – phytate P.
5FTU = phytase units.
6ND = not detected.
Table 2. Effects of microbial phytase on P balance, apparent total tract digestibility (ATTD), and standardized total tract digestibility (STTD) of P in high-lysine sorghum, red sorghum, white sorghum, and corn fed to growing pigs, Exp. 11
|
|
No phytase |
500 FTU/kg phytase2 |
|
P-value |
||||||||
|
Items |
High-lysine sorghum |
Red sorghum |
White sorghum |
Corn |
High-lysine sorghum |
Red sorghum |
White sorghum |
Corn |
SEM |
Grain |
Phytase |
Grain × phytase |
|
Feed intake, g/d |
657 |
688 |
666 |
755 |
599 |
729 |
662 |
712 |
49 |
0.061 |
0.581 |
0.619 |
|
P intake, g/d |
2.5 |
2.5 |
2.2 |
2.3 |
2.3 |
2.5 |
2.1 |
2.2 |
0.2 |
0.032 |
0.389 |
0.880 |
|
Fecal output, g/d |
78.9 |
109.6 |
83.5 |
85.7 |
66.9 |
105.8 |
83.2 |
82.9 |
7.3 |
<0.001 |
0.267 |
0.783 |
|
P in feces, % |
2.2 |
1.7 |
1.9 |
1.7 |
1.6 |
1.1 |
1.2 |
0.9 |
0.1 |
<0.001 |
<0.001 |
0.581 |
|
P output, g/d |
1.4 |
1.7 |
1.3 |
1.3 |
0.9 |
1.1 |
0.9 |
0.7 |
0.1 |
<0.001 |
<0.001 |
0.423 |
|
P absorption, g/d |
1.1 |
0.8 |
0.9 |
1.0 |
1.4 |
1.4 |
1.1 |
1.4 |
0.2 |
0.182 |
<0.001 |
0.563 |
|
ATTD of P, % |
41.9 |
28.1 |
38.5 |
41.5 |
62.3 |
56.1 |
53.9 |
66.2 |
4.8 |
0.280 |
<0.001 |
0.473 |
|
Basal EPL3, mg/d |
125 |
131 |
127 |
144 |
114 |
139 |
126 |
135 |
9.3 |
0.061 |
0.581 |
0.619 |
|
STTD of P4, % |
46.8 |
33.4 |
44.4 |
47.8 |
67.1 |
61.6 |
60.2 |
72.4 |
4.8 |
0.230 |
<0.001 |
0.480 |
1Data are means of 6 observations per treatment.
2 Phytase: Quantum Blue 5G (AB Vista, Marlborough, UK); FTU = phytase units.
3EPL = endogenous P loss. This value was estimated to be at 190 mg/kg dry matter intake (DMI). The daily basal EPL (mg/d) for each diet was calculated by multiplying the EPL (mg/kg DMI) by the daily DMI of each diet.
4Values for STTD were calculated by correcting values for ATTD for the basal endogenous loss of P.
Table 3. Apparent total tract digestibility (ATTD) of energy and digestible and metabolizable energy in high-lysine sorghum, red sorghum, white sorghum, and yellow dent corn, Exp. 21
|
Item |
High-lysine sorghum |
Red sorghum |
White sorghum |
Corn |
SEM |
P-value |
|
ATTD of GE, % |
86.7b |
85.0b |
89.4a |
89.3a |
1.0 |
0.003 |
|
As-fed basis |
||||||
|
DE, kcal/kg |
3,512a |
3,327b |
3,467a |
3,418ab |
40 |
0.004 |
|
ME, kcal/kg |
3,400a |
3,229b |
3,376a |
3,315ab |
43 |
0.012 |
|
DM basis |
||||||
|
DE, kcal/kg |
3,934a |
3,800b |
3,968a |
3,992a |
46 |
0.007 |
|
ME, kcal/kg |
3,809a |
3,687b |
3,864a |
3,871a |
49 |
0.014 |
a,bMeans within a row that do not have a common superscript differ, P < 0.05.
1Data are least square means of 8 observations for all treatments except for white sorghum (n = 7).