Elevated phosphorus Retention after facilitating phytase efficacy via intermittent feeding and acidification

Abstract

The over-exploitation of phosphorus (P) reservoir is becoming one of the major concerns in poultry industry due to the limited stock of P. Secretion of endogenous phytase in monogastric animals is insufficient to break down the phytate in plant-based diet for broilers. Thus, the addition of exogenous enzyme, e.g. phytase, is becoming essential to release P from the complex structure of phytate. Present experiment was conducted to examine the effect of interaction among three main factors including phytase, formic acid and feeding regime on growth performance and bone mineralization. 800 of male Ross 308 broiler chickens one-d-old were allocated to 4 dietary treatments, including (1) negative control (NG) diet, (2) NG with 500 FTU kg-1 of phytase, (3) NG with 1.1% of formic acid, (4) NG with same amount of phytase and formic acid, and all the treatments were fed intermittently and ad libitum. Each treatment had 10 pen replicates with 10 birds in each. Commercial starter feed was used in starter phase (1–10 d) while wheat-soy based experimental diets were provided during the grower phase (11–36 d) in pelleted form.

Overall, the results indicated that the combination of phytase, formic acid and feeding regime had a positive effect on growth performance, including feed intake, weight gain (WG) and feed conversion ratio (FCR), digestibility of P and the content of ash as well as deposition of P in tibiae. Phytase efficacy was enhanced through inclusion of formic acid, and the efficiency of such combination had more advantage under intermittent feeding. The average mortality rate was 2.38% during 11–36 d.

In addition, the interactions between and among three main factors were also observed. The interaction effect between acid and phytase on WG was found during 15–22 d. The interaction between feeding and phytase on FCR was observed between day 22–29 and this interaction also had effect on ileal P digestibility. The interaction between feeding and acid had effect on jejunal P digestibility. Also, the interaction among three main factors had no effect on ash content and deposition of P in tibiae, but, had effect on weight and width of tibiae. There were no significant differences among all treatments in terms of bone density of tibiae. The pH of the experimental diet with acid (T3) increased significantly (P < 0.001) from 4.39 to 5.02 within the first 18 hours as it exposed to the same temperature (27–29 ℃) with feeding experiment.