A Further Look at Phosphorus, Phytate, and Phytase in Monogastric Nutrition
Abstract
The objective of this dissertation was to investigate areas that needed further research with regards to phosphorus, phytate, and phytase in monogastric nutrition. To fulfill this objective, a total of 6 studies were carried out.Study 1 was designed to evaluate the additivity of apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of phosphorus (P) in mixed dies containing corn and soybean meal (SBM) and fed to broiler chickens. There were 7 dietary treatments in a randomized complete block design with body weight (BW) serving as the blocking factor. Treatments consisted of 4 semi-purified diets prepared to contain either corn or SBM as the sole source of P with or without phytase supplementation at 1,000 FYT/kg; 2 mixed diets containing corn and SBM with or without phytase addition; and a P-free diet (PFD) formulated to determine the basal endogenous loss (BEL) of P. A total of 512 day-old broiler chicks were fed a commercial starter diet for 21 days while experimental diets were fed for 3 days (day 22-24 post hatching). The BEL of P in broiler chickens as determined by the PFD was 166 mg/kg dry matter (DM). The SID of P in corn and SBM was 52.2 and 65.4 %, respectively. Phytase addition improved (P< 0.05) both the AID and SID of P in the ingredient and mixed diets. There was no difference between the predicted and determined AID and SID of P in the mixed diets and were thus additive. It was concluded that the AID and SID of P in corn and SBM were additive with or without phytase addition. However, we could not be certain if the assumption of additivity will hold true in mixed diets containing ingredients with a higher phytate content and if age of birds affected the BEL of P.In the 2nd study, the additivity of AID and SID of P in mixed diets containing corn and canola meal (CCM) was investigated in broiler chickens at 2 ages. A total of 588 broiler chickens was used in this study. Dietary treatments were arranged as a 2 × 3 × 2 factorial with 2 ages (day 13 and 21), 3 diets (corn, canola meal, and CCM), and 2 levels of phytase (0 and 1,000 FYT/kg) in a randomized complete block design. A PFD was fed to birds at both ages to determine the effects of age on the BEL of P. A commercial starter diet were fed from day 1 to 10 or 18 post hatching and then experimental diets was fed for 3 days until day 13 or 21, respectively. The AID and SID of P was higher (P < 0.05) in birds at day 13 as compared with birds at day 21 regardless of phytase addition. Similarly, the BEL of P in younger birds was higher (P< 0.01) than in older birds at d 21. Regardless of age or phytase supplementation, the predicted and determined AID and SID of P in the CCM diets were similar and thus additive. In conclusion, age influenced the BEL of P and the utilization of minerals in broiler chickens while the assumption of additivity held true when mixed diets containing CCM was fed to birds at both ages with or without phytase addition.
Degree
Ph.D.
Advisors
Adeola, Purdue University.
Subject Area
Energy|Analytical chemistry|Agronomy|Animal sciences|Chemistry|Environmental management
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