Summary
Studies have suggested a relationship between phytase activity and sodium (Na) or dietary electrolyte balance (DEB). A study was conducted to evaluate the effect of DEB on the phosphorus releasing value (PRV) of phytase in male birds fed a corn-soybean meal based diet. Dietary treatments consisted of a 2 x 4 factorial arrangement with two levels of DEB (214 and 264 meq/Kg), and four levels of supplemental phytase (0, 500, 1000, or 2000 FTU/Kg). Non phytate phosphorus (NPP) was kept at 0.12% in all the diets. Diets with no added phytase were used to build a phosphorus response curve. Each diet was fed to six replicate pens, each pen five birds each. Body weight (BW), Feed Conversion Rate (FCR) and mortality were estimated on day 18 and at the end of the trial. The toes of all birds and two tibias per cage were removed, to measure toe ash and break force, respectively. The ash and break force values were used to calculate the Phosphorus Equivalent Values (PhEV). The DEB had no significant effects on body weight, FCR, mortality, toe ash, tibia break force, or PRV. Chicks responded to increasing levels of phytase supplementation by significantly increasing body weight, improving FCR, reduction in mortality, increasing toe ash and break force, and improved PRV (P<0.05). However, there was no significant interaction between DEB and phytase supplementation, suggesting that if there is any relationship between the two factors it was not displayed in this study.
Key words: Phytase, Broilers, Sodium, Electrolyte balance.
Introduction
Phytate phosphorus, in its natural state in feed, forms complexes with different nutrients, including proteins, lipids, and minerals. Exogenous phytases not only release the phosphorus attached to the phytate acid molecule, but also the phosphorus attached to other nutrients, such as calcium and amino acids. The reduction of the cost of phytase in recent years, along with the increase in the cost of raw materials rich in phosphorus as animal protein, has led to great interest in using higher levels of phytase in broiler diets, since studies have shown an increase in phosphorus release with increasing levels of phytase (Shirley & Edwards)(2003). Recent studies indicate that phytase could influence sodium metabolism; however, Goodgame et al. (2011) could not demonstrate a relationship between the dietary needs of sodium and levels of phytase supplemented when sodium bicarbonate was used as the main source of sodium. This study was carried out to evaluate the use of phytase supplemented at normal and higher levels and its possible relationship with the Dietary Electrolyte Balance (DEB).
Materials & Methods
Nutritionally complete diets (Rostagno, 2005) of corn and soy meal were formulated to contain 0.12% of non-phytate phosphorus (FNF) and two different levels of BED through the addition of NaCl or NaHCO3. Diets containing two levels of BED were supplemented with 0, 500, 1000 or 2000 FTU/Kg of phytase (Quantum Phytase 5000XT). A phosphorus response curve was prepared with diets supplemented with increasing levels of non-phytate phosphorus, in the form of Bi-calcium phosphate, at 0 to 0.30% in 0.05% increments. BB male chicks of a commercial line (Cobb 500) were placed in cages (5 birds per cage) until day 18 days and fed different diets. Drinking water and food were supplied ad libitum during the experiment. Average weight by cage was measured at the beginning of the experiment and on day 18, when food consumption was determined. At the end of the experiment the birds were slaughtered and all the toes were used for ash determination. The tibias of two birds were used to determine break strength. Regression analysis was used to estimate the phosphorus equivalent value by phytase (PhEV) (Yan et al., 2005). Data were analyzed using ANOVA (SAS, 1991) in form of a 2 x 4 factorial array of treatments, with two BED levels and four levels of phytase supplementation, as well as the interaction thereof. P< 0.05 was used to draw statistically significant values.
Results and Discussion
There were no significant differences in BW, FCR, mortality, ash, and tibia break force or PhEV due to BED in the diet (Table 1). As expected, incremental levels of phytase significantly improved BW, FCR, ash and break force (P < 0.05). The PhEV increased with increasing levels of phytase. We found no significant interactions between the BED and the level of supplementation of phytase for any of the analyzed parameters.
Table 1. Effects of dietary electrolyte Balance (BED) and levels of Phytase on performance and Phosphorus equivalence value (PhEV) of phytase
|
|
18 d BW
(kg)
|
0-18 d
FCR
|
0-18 d
Mortality (%)
|
Ash
%
|
Break force
(kg)
|
PhEV
|
|
BED (meq/kg)
|
|
214
|
0.548
|
1.401
|
9.33
|
10.55
|
10.16
|
0.128
|
|
264
|
0.536
|
1.396
|
5.70
|
10.54
|
9.89
|
0.116
|
|
Phytase (FTU/kg)
|
|
0
|
0.454c
|
1.419a
|
17.50a
|
8.79d
|
5.87d
|
0.030
|
|
500
|
0.551b
|
1.419a
|
2.91b
|
10.34c
|
9.23c
|
0.089
|
|
1000
|
0.557b
|
1.407a
|
6.00b
|
11.18b
|
11.26b
|
0.174
|
|
2000
|
0.607a
|
1.350b
|
3.66b
|
11.86a
|
13.75a
|
0.279
|
|
BED
|
Phytase
|
|
|
|
|
|
|
|
214
|
0
|
0.458
|
1.419
|
21.67
|
8.72
|
6.04
|
0.030
|
|
214
|
500
|
0.552
|
1.414
|
3.33
|
10.20
|
9.01
|
0.113
|
|
214
|
1000
|
0.565
|
1.401
|
5.00
|
11.22
|
11.78
|
0.180
|
|
214
|
2000
|
0.617
|
1.369
|
7.33
|
12.08
|
13.82
|
0.232
|
|
264
|
0
|
0.450
|
1.418
|
13.33
|
8.86
|
5.71
|
0.030
|
|
264
|
500
|
0.551
|
1.424
|
2.50
|
10.49
|
9.46
|
0.127
|
|
264
|
1000
|
0.548
|
1.412
|
7.00
|
11.14
|
10.74
|
0.164
|
|
264
|
2000
|
0.597
|
1.332
|
0.00
|
11.65
|
13.68
|
0.218
|
|
SEM
|
|
0.008
|
0.007
|
1.533
|
0.145
|
0.365
|
0.008
|
abcd Values in the same column with different superscript differ significantly (P≤0.05).
Conclusions
The results suggest that there is no association between BED levels normally used in broilers and the activity of phytase in poultry in the first stage of growth. Consistent with previous studies, the increase in the levels of Phytase above levels normally used significantly improved the productive performance of birds.
Bibliography
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