Phosphorus equivalency of phytase with various evaluation indicators of duck in starter

Abstract

This study was conducted to evaluate phosphorus (P) equivalency of phytase with various evaluation indicators of ducks in starter (0–14 days). Three hundred and twenty 1‐day‐old Cherry Valley ducks were randomly assigned to eight groups. The dietary treatments were four levels of available phosphorus (aP) with 0.25%, 0.32%, 0.39%, and 0.46% (treatments I–IV) and four levels of phytase added to low‐aP basal diet (treatment I) with 300, 600, 900, and 1200 units (U) per kg (treatments V–VIII). The results were that compared to treatment I, increasing aP and supplementary phytase significantly (p < 0.05) improved body weight (BW), BW gain (BWG), feed intake (FI), live BW, carcass weight, semieviscerated weight, eviscerated weight, leg muscle weight, and decreased feed conversion ratio (FCR). Treatments V and VI did not significantly increase tibia ash, tibia calcium, and tibia P of 14‐day‐old ducks (p > 0.05). Following the increase of aP level (treatments I–IV), apparent utilization of Ca and P of ducks increased with varying degrees. With the increase of dietary phytase level (treatments V–VIII), the apparent utilization of Ca and P showed no significant difference (p > 0.05) but an increasing trend. Serum P reached the highest level when adding 600 U/kg phytase (treatment VI). Serum Ca and serum alkaline phosphatase activity showed no significant difference among treatments V–VIII (p > 0.05). Based on corn–soybean–rapeseed meal diet, with the evaluation indexes of FI, BWG, tibia ash, tibia Ca, tibia P, and apparent utilization of Ca and P, the addition of 500 U/kg phytase could release aP of 0.03%, 0.04%, 0.02%, 0.01%, 0.02%, 0.08%, and 0.07%, respectively. On the same way, the addition of 1000 U/kg phytase could release aP of 0.07%, 0.09%, 0.06%, 0.02%, 0.07%, 0.09%, and 0.09%, respectively.

Digestible calcium equivalency of phytase and nutrient utilization of broiler chickens fed graded levels of limestone or phytase during the starter phase

“…However, there has been no attempt to estimate the digestible Ca equivalency of phytase relative to limestone in broiler chickens, which might be partly due to the seeming inertia towards moving to a digestible Ca system in the diet formulation of broiler chickens until recently ( Walk et al, 2021 ), and the relatively cheaper cost of supplementing Ca via inorganic sources such as limestone as compared to inorganic P sources. To the authors' knowledge, this study represents the first attempt to determine the digestible Ca equivalency of phytase by employing varying concentrations of limestone in a similar manner to the use of graded inorganic P in deriving the P equivalence of phytase ( Jendza et al, 2006 ; Zhang et al, 2022 ). One limitation in the current study, possibly contributing to the observed low R -squared values in the regression equations, is the inability to match the range of digestible Ca resulting from feeding graded Ca levels from limestone with graded phytase supplementation.…”

“…The regression equations for ileal digestible Ca on supplemental Ca or phytase were expressed by linear and nonlinear models, respectively ( Jendza et al, 2006 ; Zhang et al, 2022 ). The dependent variable (digestible Ca) was regressed against independent variables (calculated inorganic Ca from limestone or phytase intake).…”

“…Equivalency studies aid in determining the additional release of a particular nutrient in response to a dietary treatment for a known physiological purpose ( Adedokun et al, 2004 ). Most studies conducted to determine digestible P equivalency values for phytase use an optimal dietary level of Ca with a low level of nonphytate P as a baseline, to which phytase or inorganic P are then added at various increments ( Driver et al, 2005 ; Jendza et al, 2006 ; Zhang et al, 2022 ). As such, the responses elicited in such experiments are due to the combined effect of alleviating a P deficiency through the liberation of phytate-P by the enzyme and the reduction of Ca to P ratio imbalance.…”