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Effects of high levels of phytase in low lysine diets on the growth performance of nursery pigs
Two studies were conducted to determine the effects of added phytase in nursery diets formulated at or below their Lys requirement. In both studies, diets with the lowest phytase levels were formulated to meet the available P requirement. In Exp. 1, 360 barrows (PIC 327 × 1050; initially 12.4 kg) were used in an 18-d study with 5 pigs per pen and 18 pens per treatment in a university research facility. Pens were randomly allotted to diets in a 2 × 2 factorial with main effects of Lys level (adequate vs. marginal; 1.20% vs. 1.05% standardized ileal digestible [SID] Lys) and phytase level (500 vs. 3,000 FYT/kg; Ronozyme®HiPhos®, DSM). Overall (d 0 to 18), there were no (P>0.05) lysine × phytase interactions and no differences were observed between phytase levels. Pigs fed adequate Lys diets had greater (P<0.01) ADG, G:F, and BW than those fed marginal Lys. In Exp. 2, 2,592 nursery pigs (PIC 337 × 1050; initially 10.4 kg) were fed 1 of 6 diets over 2 phases in a 36-d commercial research study. There were 27 pigs per pen and 16 pens per treatment. Dietary treatments included an adequate Lys (1.20 and 1.10% SID Lys in Phase 1 and 2, respectively) positive control diet containing 250 FYT/kg of phytase, or 5 low Lys (1.10 and 1.00% SID Lys in Phase 1 and 2, respectively) diets with 250, 500, 1,000, 2,000, or 3,000 FYT/kg of phytase. Overall (d 0 to 36), pigs fed the positive control had greater (P<0.02) ADG and G:F than pigs fed the low-Lys diet (Table). Increasing phytase increased (quadratic, P<0.02) ADG with maximum response at 1,000 FYT/kg. Phytase did not affect G:F. In summary, these studies illustrate the importance of feeding adequate Lys to optimize ADG and G:F. Additionally, the trials show a difference between university and commercial settings because only the commercial study yielded a detectable phytase response, where pigs fed the low-Lys diet with 1,000 FYT/kg phytase had performance similar to pigs fed high Lys diets containing 250 FYT/kg phytase.
Keywords: phosphorus, phytase, nursery pigs
P< |
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SID Lys: |
High |
Low |
Phytase |
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Phytase, FYT/kg: |
250 |
|
250 |
500 |
1,000 |
2,000 |
3,000 |
SEM |
Lysine |
Linear |
Quadratic |
||||
ADG, kg |
0.57 |
0.54 |
0.55 |
0.57 |
0.57 |
0.55 |
0.008 |
0.02 |
0.10 |
0.02 |
|||||
ADFI, kg |
0.88 |
0.88 |
0.88 |
0.89 |
0.91 |
0.88 |
0.016 |
0.74 |
0.44 |
0.23 |
|||||
G:F |
0.644 |
0.618 |
0.632 |
0.636 |
0.626 |
0.632 |
0.007 |
0.01 |
0.34 |
0.29 |
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