The Effects of Phytase in Nutritionally Adequate Diets,Diets Deficient in Calcium and Phosphorus, and the Interactive Effects of Phytase and Eimeria Acervulina Infection in Broiler Chicks
Six experiments were conducted to determine the interactive effects of Eimeria acervulina (E. acervulina) infection and phytase, and the effects of phytase in nutritionally adequate diets and in diets deficient in Ca and available P (aP). Corn-soybean meal (C-SBM) diets were used. In Exp 1, treatments were: 1) C-SBM, 1.0% Ca and 0.45% aP; 2) C-SBM, 0.80% Ca and 0.25% aP; 3) Diet 1 + 600 FTU phytase/kg; 4) Diet 2 + 600 FTU phytase/kg; 5 to 8) Diets 1 to 4 but infected with coccidiosis. Weight gain (ADG), feed intake (ADFI), and gain:feed were reduced (P < 0.01) by the coccidial infection and the reduction in Ca and aP. Phytase increased (P < 0.02) ADG and ADFI, regardless of the Ca and aP content of the diet or the presence of coccidiosis. Gain:feed was increased by phytase but only in uninfected chicks (phytase x coccidiosis interaction, P < 0.02). Phytase increased (P < 0.02) bone ash percentage but only in diets deficient in Ca and aP (P < 0.01). Experiments 2 and 3 included only treatments 1 to 4 of Exp 1. The reduction in Ca and aP reduced (P < 0.01) ADG, ADFI, and gain:feed. Phytase addition increased (P < 0.02) ADG and ADFI in diets deficient in Ca and aP and in the nutritionally adequate diets. Experiments 4, 5, and 6 were conducted to determine the effects of phytase on intestinal transit time in broilers. Diets were: 1) C-SBM, 0.9% Ca and 0.35% aP; 2) C-SBM, 0.80% Ca and 0.25% aP + 600 FTU phytase/kg. Transit time on Day 1, but not on Day 7, was faster (P < 0.03) in chicks fed phytase. These data indicate that phytase is effective in the presence of a coccidial infection, but it may not be as effective as in uninfected chicks. Futhermore, phytase increases growth in diets deficient in Ca and aP and in diets formulated to be adequate in all nutrients. This increase in growth may be due to a faster transit time of feed through the digestive tract, resulting in a greater feed intake and gain.
Advisor:L. Lee Southern; Marcos Fernandez; Tom Bidner
School:Louisiana State University in Shreveport
School Location:USA - Louisiana
Source Type:Master's Thesis
Keywords:animal science dairy and poultry sciences
Date of Publication:07/12/2002