Effect of the addition of a novel phytase to corn and soybean based diets for broilers

Introduction

Phosphorous just as nitrogen and potassium, are essential nutrients for plants and are added to soils as fertilizers to improve yields. Plants absorb phosphorous as phytic acid, but it is not available for monogastric animals. Vegetable-origin food, particularly corn and soybean meal, are added in big amounts to the majority of bird diets. For this reason, inorganic sources need to be added to meet the bird's requirements without affecting their performance. However, this practice affects the environment as the phosphorous excreted increases the eutrophication of waters thus reducing their quality and negatively affecting the life of aquatic animals. Plus, phosphorous is a non-renewable element, the third most expensive nutrient and has no substitute in animal feeds. Besides that, the increased demand for inorganic phosphorous by the agricultural and livestock systems plus the expectations that it may reach its maximum production peak by 2030, make it necessary to find alternatives that may help reduce the use of the supplement in feeds and thus its excretion to the environment (Cordell et al., 2009).

As part of the alternatives found, phytases have received special attention since this enzyme breaks down the phytate molecule and not only makes the phosphorous available, but other minerals and amino acids too and the excretion is reduced. The search for new phytases with a relatively higher resistance to intestinal hydrolysis and greater heat stability is an on-going process (Dilger et al., 2004).

For these reasons, the objective of this paper was to evaluate the effect of the use of a novel bacterial-origin phytase - Aspergillus oryzae (RONOZYME HiPhos, DSM Nutritional Products) in diets based on corn and soybean meal, on performance, bone parameters and phosphorous utilization in 7 - 21 day old broilers.

Materials and Methods

The experiment was carried out in the Poultry Sector of the School of Zootechnics and Agricultural Sciences of Viçosa Federal University.

From hatching out until day 7 of age, the chicks were bred on wood-ss bedding, they were given feed and water "ad libitum" with adequate amount of feed for the pre-initial state (24% protein), as per the recommendations of Rostagno et al. (2005), with the exception of Ca and Pd (0,8 y 0,35% respectively). During the experimental period (8 to 21 days), 560 Cobb broilers were used with an initial mean weight of 0,209 kg, housed in metabolic cages, distributed on an experimental randomized outline with 7 treatments, 8 replicates and 10 birds per experimental unit.

A baseline diet consisting of corn and soybean meal was used, meeting the recommendations for chicks in the initial phase (8 to 21 days) (Rostagno et al., 2005), with the exception of P and Ca which were fitted with dicalcium phosphate (PB) y calcite carbonate, obtaining values of 0,17% Pdisp and 0,95% total Ca. The chemical composition of the phosphorous sources was previously determined in order to enable the proper formulation of experimental feeds (Table 1).

Table 1. Phosphorous content of ingredients used in experimental feeds for broilers from 7 to 21 days (in natural matter)

Ingredient	Total phosphorous, %	Total calcium, %
Corn	0,24	0,026
Soybean meal	0,53	0,235
Dicalcium Phosphate	18,56	24,46
Calcite Carbonate	-	38,67

The experimental treatments were: T1: Baseline Feed (RB); T2: RB + 0,06% phosphorous FB; T3: RB + 0,12% phosphorous FB; T4: RB + 0,18% phosphorous FB; T5: RB + 500 FYT/kg feed; T6: RB+1000 FYT/kg feed; T7: RB+2000 FYT/kg feed (Table 2).

The experimental period was 14 days and weight gain, feed intake and feed conversion were evaluated. Excreta were collected from days 16 to 20 in order to determine the phosphorous balance in ((total P intake - total P excreted / total P intake) x 100).

On day 21 all birds were slaughtered to obtain the tibia and ileal content (40 cm of terminal ileum). The bone parameters evaluated were: weight of the dry and defatted tibia (g) , tibia ashes (% and g) and tibia phosphorous (% and mg).). The apparent ileum digestibility of phosphorus was determined by the fecal indicator method and using the acid insoluble ash (CAI).

The measurements from the parameters evaluated in treatments 1 to 4, were used to obtain a lineal equation (Pattern Curve) and later the measurements from treatments 5 to 7 -which contained phytase- were used to estimate the phosphorous value of each phytase level as per the methodology recommended by Sakomura & Rostagno (2007).

Table 2. Composition of experimental diets used from 8 to 21 days old

	Treatments
	T1	T2	T3	T4	T5	T6	T7
Corn	54,63	54,63	54,63	54,63	54,63	54,63	54,63
Soybean meal	38,10	38,10	38,10	38,10	38,10	38,10	38,10
Soybean oil	2,60	2,60	2,60	2,60	2,60	2,60	2,60
Salt	0,432	0,432	0,432	0,432	0,432	0,432	0,432
Premix Vit¹	0,12	0,12	0,12	0,12	0,12	0,12	0,12
Premix Min²	0,05	0,05	0,05	0,05	0,05	0,05	0,05
DL-Met	0,305	0,305	0,305	0,305	0,305	0,305	0,305
L-Lysine HCl	0,10	0,10	0,10	0,10	0,10	0,10	0,10
L-Treonine	0,01	0,01	0,01	0,01	0,01	0,01	0,01
Coline60%	0,10	0,10	0,10	0,10	0,10	0,10	0,10
BHT³	0,01	0,01	0,01	0,01	0,01	0,01	0,01
Coxistac³	0,055	0,055	0,055	0,055	0,055	0,055	0,055
*Sub-Total*	96,512	96,512	96,512	96,512	96,512	96,512	96,512
Calcitic carbonate	1,795	1,586	1,376	1,166	1,795	1,795	1,795
Dicalcium Phosphate	0,293	0,617	0,941	1,266	0,293	0,293	0,293
Celite	1,40	1,285	1,171	1,056	1,399	1,398	1,396
Phytase	-	-	-	-	0,001⁵	0,002⁶	0,004⁷
*Total*	100	100	100	100	100	100	100
*Estimated composition*
EM Kcal/Kg	3,00	3,00	3,00	3,00	3,00	3,00	3,00
PB, %	22,3	22,3	22,3	22,3	22,3	22,3	22,3
P Total, %	0,39	0,45	0,51	0,57	0,39	0,39	0,39
P Available, %	0,17	0,23	0,29	0,35	0,17	0,17	0,17
Ca Total, %	0,9	0,9	0,9	0,9	0,9	0,9	0,9
Analized composition
PB, %	22,41	22,44	22,41	22,44	22,39	22,37	22,32
P Total, %	0,381	0,443	0,512	0,570	0,384	0,389	0,384
Ca Total, %	0,914	0,912	0,912	0,913	0,915	0,915	0,913
Ash, %	7,16	7,19	6,95	6,90	7,07	7,03	7,01

^{1 Content per kg: Vit. A - 15.000.000 UI; Vit. D3 - 1.500.000 UI; Vit E - 15.000 UI; Vit B1 - 2,0 g; Vit B2 - 4,0 g; Vit B6 - 3,0 g; Vit B12 -0,015 g; Nicotinic acid - 25,0 g; Pantotenic Ac - 10,0 g; Vit. K3 - 3,0 g; Folic Ac-1,0 g; Selenium - 0,25 g; antioxidant - 10,0 g e excipient q.s.p. - 1000 g. 2 Content per Kg: Manganese - 80 g; Iron - 80 g; Zinc - 50 g; Copper - 10 g; Cobalt - 2 g; mud - 1 g e excipient q.s.p. - 500 g. 3 Butylhydroxytoluene, 4Coxistac: (Salinomycin sodium 12%; 66 ppm), 5 500 FYT: 10 g/ton, 6 1000 FYT: 20g/ton, 7 2000 FYT: 40 g/ton}

Results and Discussion

The increase in inorganic phosphorus (PI) levels and the addition of phytase, improved weight gain, feed conversion, bone mineralization and phosphorous usage (Linear, P<0,01), table 3.

These results are similar to those found by Dilger et al. (2004), who observed a linear improvement (P<0,01), for the following performance parameters: bone mineralization and phosphorous usage with the addition of phytase to broilers diet. The effect of phytase supplementation in diets of 21 day old broilers, has been reported by several authors as positive (Sebastian et al., 1998; Dilger et al., 2004;), in contrast, other authors did not see such effect (Perney et al., 1993). Such contrasting results may be due to various factors such as the phytase source, ingredients (type, source, phytate content) and diet characteristics (processing, level of vitamin D and Ca:P ratio (Ravindran et al., 1995).

Table 3. Effect of the addition of inorganic phosphorous and phytase on the performance parameters: bone mineralization and use of phosphorous in 8-21 day old broilers

	P Level (%)	Phytase addition (FYT)
0	0,06	0,12	0,18	500	1000	2000
Weight gain (g)¹	0,42	0,66	0,77	0,81	0,70	0,72	0,73
Feed Conversion (g/g)¹	1,54	1,27	1,15	1,13	1,20	1,16	1,13
Tibia weight (g)¹	0,89	1,06	1,17	1,24	1,09	1,18	1,20
Ashes (%)¹	41,56	49,64	51,63	53,64	49,62	51,64	52,43
Ashes (g)¹	0,37	0,53	0,60	0,67	0,54	0,61	0,63
Phosphorous in tibia (%)¹	4,86	5,79	6,01	7,09	6,85	6,92	7,06
Phosphorous in tibia (mg)¹	43,21	61,67	70,13	88,23	74,87	81,55	84,50
Phosphorous balance (%)¹	64,68	68,31	71,31	74,71	69,51	71,48	73,54
Apparent Ileal Digestibility (%)¹	62,62	64,05	67,98	75,60	66,41	68,40	74,08

^{1 Anova: P Level Linear effect (P<0,01); Phytase effect (P<0,01).}

Conclusions

The addition of HiPhos phytase improves weight gain, feed conversion, bone mineralization, apparent digestibility and phosphorous retention in male broilers during the initial period.

Bibliography

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