The area in which soybeans are grown is known to affect various aspects of the chemical composition of soybean meal produced from those soybeans. However, it is not known if there is a difference in the concentration of phytate, and therefore in phosphorus digestibility, among soybeans from different growing areas. Therefore, an experiment was conducted to determine the concentration of phytate and the apparent (ATTD) and standardized (STTD) total tract digestibility of phosphorus in soybean meal produced from soybeans grown in four different areas in the United States. A secondary objective was to determine the effect of microbial phytase on STTD of P in soybean meal from each of the four areas.
Experimental design
Twenty sources of soybean meal were used in the experiment. Soybeans were sourced from crushing plants located throughout the soybean growing area of the U.S.. For analysis, the crushing plant locations were separated into 4 zones: 1) northern growing area (Michigan, Minnesota, and South Dakota; 4 samples), 2) eastern growing area (Georgia, Indiana, and Ohio; 5 samples), 3) western growing area (Iowa, Missouri, and Nebraska; 6 samples), and 4) Illinois (5 samples).
Two hundred growing barrows (initial BW: 16.90 ± 1.79 kg) were fed one of eight diets. The diets were based on cornstarch, sucrose, soybean oil, and soybean meal from each of the four zones. Soybean meal was the only source of phosphorus in the diets. For each source of soybean meal, one diet contained no microbial phytase, and another was formulated with 500 units/kg of microbial phytase.
Phosphorus content
Total concentration of phosphorus in soybean meal did not differ among the four zones, except for a tendency (P < 0.10) for a reduced concentration of phosphorus in soybean meal from Zone 1 compared with soybean meal from Zone 3 (Table 1).
The percentage of phosphorus bound to phytate in soybean meal from Zone 2 did not differ from that in soybean meal from Zones 1 and 4, but was greater (P < 0.05) than that in soybean meal from Zone 3.
Phosphorus digestibility
Addition of phytase increased (P < 0.05) ATTD and STTD of phosphorus in all diets (Table 2). The increases in ATTD and STTD of phosphorus caused by the addition phytase were less (P < 0.05) for soybean meal from Zone 4 than for the other sources.
Key points
- The phosphorus content was not different among soybean meals produced from soybeans grown in the northern growing area, eastern growing area, western growing area, and Illinois.
- The growing area of soybeans does not influence the ATTD or STTD of phosphorus by pigs.
- The addition of microbial phytase increased the ATTD and STTD of phosphorus in soybean meal from all zones.
Table 1. Phosphorus content of soybean meal (as-fed basis)
|
Zone1 |
|||||||
|
Item |
1 |
2 |
3 |
4 |
Average2 |
SEM |
P-value3 |
|
n |
4 |
5 |
6 |
5 |
- |
- |
- |
|
DM, % |
88.6 |
88.71 |
88.3 |
89.03 |
88.66 |
0.39 |
0.18 |
|
P, % |
0.63 |
0.65 |
0.67 |
0.64 |
0.65 |
0.01 |
0.09 |
|
Phytate, % |
1.43 |
1.53 |
1.5 |
1.46 |
1.48 |
0.04 |
0.27 |
|
Phytate-bound P, % |
0.4 |
0.43 |
0.42 |
0.41 |
0.42 |
0.01 |
0.16 |
|
Phytate-bound P, % of total P |
63.75ab |
66.54a |
63.43b |
64.06ab |
64.44 |
1.02 |
0.04 |
|
Nonphytate P, % |
0.23ab |
0.22b |
0.25a |
0.23ab |
0.23 |
0.01 |
0.01 |
|
Nonphytate-bound P, % of total P |
36.26ab |
33.45b |
36.57a |
35.94ab |
35.56 |
1.02 |
0.04 |
a-dMeans within a row lacking a common superscript are different (P < 0.05).
1Zone 1 = northern growing area (MI, MN, and SD); Zone 2 = eastern growing area (GA, IN, and OH); Zone 3 = western growing area (IA, MO, and NE); Zone 4 = IL.
2Average is for the 20 sources of soybean meal.
3P-values for comparison of the 4 zones.
Table 2. Effects of phytase on apparent (ATTD) and standardized (STTD) total tract digestibility of phosphorus in SBM from different zones of the United States
| Zone1 | ||||||||||||
| 1 | 2 | 3 | 4 | |||||||||
| Phytase Units, FTU/kg | P-value | |||||||||||
| Item | 0 | 500 | 0 | 500 | 0 | 500 | 0 | 500 | SEM | Zone | Phytase | Zone × Phytase |
| ATTD of P, % | 50.61 | 65.89 | 51.42 | 64.61 | 49.69 | 63.58 | 55.44 | 64.71 | 1.76 | 0.09 | 0.01 | 0.01 |
| STTD of P, % | 56.96 | 72.23 | 57.56 | 70.81 | 55.74 | 69.88 | 61.29 | 71.13 | 1.75 | 0.08 | 0.01 | 0.04 |
1Zone 1 = northern growing area (MI, MN, and SD); Zone 2 = eastern growing area (GA, IN, and OH); Zone 3 = western growing area (IA, MO, and NE); Zone 4 = IL
This report is based on research by Kelly Sotak-Peper and Hans H. Stein, published in Sotak-Peper's Ph. D. dissertation.