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Efficiency of Ca and P retention in growing pigs fed diets with different Ca:P ratios provided by monocalcium phosphate or phytase supplementation
The dietary Ca:total P ratio (Ca:tP) may affect Ca and P retention and interfere with phytase (Phy) activity. However, limited data are available on responses to Ca:tP less than 1. A 32-d experiment with 161 crossbred (1/4 Landrace X 1/4 Large White X 1/2 PIC Line 19) gilts and barrows (initial BW 26.1±0.39 kg) was designed to determine Ca:tP and Phy effects on growth and bone accretion. Pigs were randomly allotted within weight blocks to 1 of 7 dietary treatments with 7 to 8 pigs/pen (sex balanced) to provide 3 pens per treatment. Dietary corn-SBM based treatments were arranged as a 2 X 3 factorial design with 2 Phy levels (0 vs 650 FTU/kg diet from Ronozyme HiPhos (GT2700) and 3 Ca:tP (0.8:1, 1.1:1 or 1.5:1). Diets provided 90% of the tP requirements with additions of monocalcium phosphate (MCP) or Phy. A positive control (PC) diet provided 100% of tP requirements with MCP and 1.2:1 Ca:tP. On d-32, 2 pigs per pen were selected and scanned by dual energy X-ray absorptiometry (DXA) to determine whole body bone mineral content (BMC). BMC gain and ADFI were used to estimate Ca and P retention, and retention efficiency (RE, g retained/g consumed). Regardless of the P source, ADG, ADFI, BMC gain, Ca and P retention were greater at 0.8:1 vs.1.5:1 Ca:tP. However, Ca and P RE decreased if Ca:tP increased. In contrast with MCP diets, no differences in ADG and BMC gain were detected among PC and diets with Phy at 0.8:1 or 1.1:1 Ca:tP. Pigs supplemented with Phy at 0.8:1 Ca:tP had the greatest Ca RE and a greater P RE than PC and MCP diets. In conclusion, a reduction in Ca:tP to 0.8:1 in Phy supplemented diets improved growth and bone traits as these pigs used dietary Ca and P more efficiently than pigs fed diets with 1.5:1 Ca:tP.
|
Phytase, FTU/kg |
|
||||||||
|
0 |
|
0 |
|
650 |
|
||||
|
Ca:tP ratio |
|
||||||||
Traits |
1.2:1 |
|
0.8:1 |
1.1:1 |
1.5:1 |
|
0.8:1 |
1.1:1 |
1.5:1 |
SEM |
ADG, kg/d |
0.97ab |
|
0.94b |
0.91bc |
0.87c |
|
1.02a |
0.96ab |
0.92bc |
0.021 |
ADFI, kg/d |
1.97ab |
|
1.95bc |
1.91bc |
1.87c |
|
2.06a |
1.96bc |
1.94bc |
0.044 |
Gain BMC, g/d |
13.9a |
|
9.89b |
7.77c |
6.90c |
|
12.03a |
12.22a |
8.68bc |
0.722 |
Ca retention efficiency |
0.39c |
|
0.47b |
0.31d |
0.21e |
|
0.75a |
0.52b |
0.29d |
0.027 |
P retention efficiency |
0.32bc |
|
0.27c |
0.20d |
0.20d |
|
0.34ab |
0.38a |
0.27c |
0.020 |
Means within a row without a common superscript are different, P <0.05.
Keywords: phytase, calcium:total phosphorous ratio, growth, bone accretion, retention