Use of a novel phytase on mineral availability and broiler performance

The majority of poultry feeds is composed by plant-origin ingredients of which most of the phosphorus (P) and calcium (Ca) and other minerals with a positive charge are present in the form of insoluble phytate (Maenz, 2001). Phytate is considered an antinutritional factor for monogastrics, since it structure includes highly ignitable orthophosphate groups, rious for cation availability such as calcium, zinc, copper, magnesium, and iron in the gastrointestinal tract, resulting in the formation of insoluble complexes (Sohail and Roland, 1999). Monogastric animals cannot digest phytic acid properly, since they lack or produce only limited amounts of the necessary enzymes (Zhou et al., 2008). In addition to increasing production costs, the low digestibility of phytic P also increases the excretion of this mineral to the environment. The use of enzymes leading to make the most of phytic P in cereals is one of the most popular alternatives in animal nutrition. Phytases hydrolyze phytic P and release inorganic P, and they are naturally found in plant seeds, bacteria, molds and yeast (Casey and Walsh, 2004). In addition to improve performance and decrease inclusion levels of inorganic P, one of the reasons for the increased market shares of commercial phytases is the environmental pollution-related legislation, since their use as feed additives is mandatory in Europe, South East Asia, South Korea, Japan, and Taiwan (Maiorka and Fbirdro, 2009). Several factors influencing animal responses to various phytase types, including their molecular properties. It has been said that some phytases have limited stability in the gastric environment, when compared to the new generation, bacterial phytases (Ravindran et al., 2008). One of the means of evaluating P availability to be affected by phytases is evaluating animal performance using diets with reduced P inclusion levels. The objective of this study was to evaluate feed intake (FI), weight gain (WG), feed conversion rate (FCR), and mortality in broilers fed deficient P levels, but supplemented with increasing levels of a novel, bacterial-origin phytase expressed in Aspergillus oryzae (Ronozyme HiPhos, DSM Nutritional Products).

Four hundred and twenty (420) one-day-old, male, Cobb 500 chicks were used. The birds were placed in metal, battery cages with controlled temperature. The experimental design was completely at random with 7 treatments and 6 10-bird repetitions (Table 1). The experimental feeds were based on corn and soybean meal for the experimental period from 1 to 24 days of age. Prior to formulation, the ingredients were analyzed for their Ca and P contents. Samples were collected from all experimental feeds as to determine Ca, P, and crude protein (CP) levels, as well as for the recovery of the added phytase. Animal performance was evaluated weekly, while the FCR was corrected for the weight of any dead birds. Mortality was recorded periodically, categorized as per the probable cause. At the end of the experimental period, total excreta were collected from day 21 to day 24. At the end of day 24, 3 birds per repetition were euthanized in order to collect the right tibia, which was cleaned and defatted as to determine ash, Ca, and P contents. The PROC GLM and PROC REG packages (SAS, 2001) were used for the statistical analysis of the results. Tukey´s test was used for mean comparisons.

Table 1. Experimental treatments

As seen in Table 2, the reduction of available P in the feeds showed a condition of mineral deficiency resulting in decreased animal performance, and a significant increase in mortality, mostly due to locomotive problems. The supplementation of increasing phytase levels in the feeds containing 0.17 available P  resulted in improved WG and FCR, and significantly decreased mortality, matching the results reported by Scheideler and Ferket (2000), who found decreased incidence of tibial dischonlasia in broilers fed low available P feeds, supplemented with phytase.

Table 2. Performance and locomotive problem-associated cumulative mortality in the birds from 1 to 21 days of age

When analyzed by regression curves, results in Table 2 show statistical equivalence of performance values. Therefore, it can be stated that the inclusion of 500, 1,000 and 2,000 FYT release approximately 0.053, 0.14 and 0.196 available P, in average, for WG, FCR, and tibial ash, respectively. The effect of the enzyme on tibial ash, Ca and P deposition can be seen in Table 3. The percent levels shown in Table 3 does not take into account bone weights. The value found in T1 is superior to all others, even though bone weights with this treatment was lower than those in all other treatments. The concentrations of 1,000 and 2,000 FYT were statistically equal to the positive control (T4) thus proving increased mineral tibial deposition with P-deficient/phytase-supplemented feeds. Results show increased ash, Ca and P deposition in the tibia with the feeds supplemented with 500, 1,000 and 2,000 FYT, as compared to the control treatments, consistent with the report by Han et al. (2009). Digestibility values were estimated (Table 4) using the following equation: (mineral content intake - mineral content excreted) / mineral content intake x 100). The low P/phytase-supplemented feeds resulted in the improved digestibility of P at the levels of 1,000 and 2,000 FYT, in agreement with Santos et al. (2008). P digestibility is improved with low available P levels + phytase supplementation, which proves the hydrolysis of phytic acid-bound P (Zhou et al., 2008; Santos et al., 2008). Least cost formulation software programs, are not prepared or adjusted to the benefits (that increase in a linear fashion) associated to the dose (which increases in a log fashion) (Maiorka, 2009) as seen in this study. The regression equations in response to phytase inclusion are shown in Table 5.

Table 3. Effect of treatments on ash, Ca and P concentrations in the tibia of broilers at 24 days of age

Table 4. Effect of treatments on dry matter (DM), Ca and P digestibility from 21 to 24 days of age

Table 5. Regression equations in response to the inclusion of phytase in the diet, from 1 to 21 days of age

The use of this novel phytase resulted in benefits at all dose rates, and different responses in agreement to inclusion levels. Dose equivalence, considering the parameters of weight gain, feed conversion rate, and tibial ash was 0.053 available P for 500 FYT; 0.140 for 1,000 FYT and 0.196 for 2,000 FYT.

Casey A & Walsh G. 2004. Identification and characterization of a phytase of potential commercial interest, Journal of Biotechnology 110:313-322.

Han JC, Yang XD, Qu HX, Xu M, Zhang T, Li WL, Yao JH, Liu YR, Shi BJ, Zhou ZF, Feng XY. 2009. Evaluation of equivalency values of microbial phytase to inorganic phosphorus in 22- to 42-day-old broilers. Journal of Applied Poultry Research 18:707-715.

Maenz DD. 2001. Enzymatic characteristics of phytases as they relate to their use in animals feeds. pp 61-84. In: Bedford MR & Partridge GG (Eds) Enzymes in farm animal nutrition. Wallingford: Cab Publishing.

Maiorka A & Fbirdro A. 2009. Avaliando o uso de enzimas NSP e fitases visando a melhora de desempenho e custos de dietas de birds e suínos. In: CBNA, Campinas. CBNA.

Ravindran V, Cowieson AJ, Selle PH. 2008. Influence of Dietary Electrolyte Balance and Microbial Phytase on Growth Performance, Nutrient Utilization, and Excreta Quality of Broiler Chickens. Poultry Science 87:677-688.

Santos FR, Hruby M, Pierson EEM, Remus JC, Sakomura NK. 2008. Effect of Phytase Supplementation in Diets on Nutrient Digestibility and Performance in Broiler Chicks. Journal of Applied Poultry Research 17:191-201.

Scheideler SE & Ferket PR. 2000. Phytase in Broiler Rations - Effects on Carcass Yields and Incidence of Tribal Dyschonlasia. Journal of Applied Poultry Research 9:468-475.

Sohail SS & Roland DA. 1999. Influence al supplemental phytase on performance of broilers four to six of age. Poultry Science 78:550-555.

Zhou JP, Yang ZB, Yang WR, Wang XY, Jiang SZ, Zhang GG. 2008. Effects of a New Recombinant Phytase on the Performance and Mineral Utilization of Broilers Fed Phosphorus-Deficient Diets. Journal of Applied Poultry Research 17:331-339.