Efficacy of exogenous phytase in broiler chickens and pigs

Edward Koopmann Addo-Chidie, Purdue University

Abstract

An efficient use of phytase enzyme requires clearer understanding of the interactive effects of other dietary factors. Prominent among these factors are dietary Ca and P. There is also a need to ascertain the P equivalency of the various forms of phytase under these dietary conditions to arrive at precise phytase doses. Three experiments were conducted. The first experiment was to determine the influence of a highly soluble calcium source (HSC) and phytase on broiler grower performance, bone ash, and apparent ileal Ca and P digestibility. The corn-soy based dietary treatments consisted of four levels of Ca (9, 7.5, 6.0, or 4.5 g/kg) from HSC and three levels of phytase (0, 500, or 2500 FTU /kg) in a 4 X 3 factorial arrangement making 12 diets. All 12 diets were kept at a non phytate phosphorus (nPP) level of 3.2 g/kg. In addition, a positive control (PC) diet was composed of 9 g/kg Ca from limestone and 4.5 g/kg nPP. Feed intake (FI) was linearly reduced (P ≤ 0.05), and body weight gain (BWG) was quadratically increased (P ≤ 0.05) as Ca from HSC was reduced from 0.90% to 0.45%. Phytase supplementation linearly increased (P ≤ 0.05) feed intake (FI) xii and body weight gain (BWG) and improved gain: feed (G: F). Phytase supplementation increased tibia ash weight and tibia P (g) in broilers fed 0.60, 0.75, or 0.90% HSC (Ca level x phytase P ≤ 0.05). Reducing HSC from 0.90 to 0.45% or increasing phytase supplementation linearly improved (P ≤ 0.05) P digestibility. In conclusion, feeding HSC with phytase allowed for reductions in dietary Ca while maintaining broiler performance and bone mineralization. In experiment 2, 864 three day old chicks (Ross 708) were used in a 20-d experiment to compare the phytase equivalence of two phytase products (Phytase A and Phytase B). Eight corn-soybean based diets consisting of a positive control (PC) diet (4.5 g/kg nPP) , three negative control (NC) diets (1.5, 2.5 and 3.5g/kg nPP) labeled as diets NC1, NC2 and NC3, respectively; two diets comprising of NC1(1.5 g/kg) plus Phytase A at two inclusion levels (500 FTU or 1000 FTU) and two more diets comprising of NC1 (1.5 g/kg) plus Phytase B at two inclusion levels (500 FTU or 1000 FTU). Supplementation of NC1 with Phytase A or B linearly (P ≤ 0.05) increased BWG, FI and G: F ratio. Both phytase increased (P < 0.05) tibia ash. In contrast with Phytase A, there was an increase (P ≤ 0.05) in ileal P digestibility response to Phytase B. Phytase B was superior (P ≤ 0.05) to Phytase A in terms BWG, FI tibia weight, and apparent ileal P digestibility. In conclusion, for most of the responses considered in this study, Phytase B was more efficacious compared to Phytase A for most of the response criteria. Experiment 3 was conducted to compare the efficacy of two phytase products on 15-kg pigs fed corn-soyben meal based diets. Forty-eight barrows xiii were assigned to 6 diets resulting in 8 pigs per diet in a randomized complete block design. The diets consisted of a positive control (PC) diet (5.8 g/kg P), a negative control (NC) diet (3.7 g/kg P), two diets consisting of the NC supplemented with 250 or 500 FTU/kg diet of Phytase 1 and two more diets from supplementing the NC with 250 or 500 FTU/kg diet of Phytase 2. Supplementation of the NC diet with Phytase 1 or 2 increased P and Ca digestibility. Response of pigs to both phytases was linear (P < 0.05) for energy intake, energy absorbed and energy retained. Energy absorbed and retained were lower for NC when compared with PC. Although there was a linear response to both phytases, there was not a clear difference between the two products.

Degree

M.S.

Advisors

Adeola, Purdue University.

Subject Area

Animal sciences

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