Effect of early dietary energy restriction and phosphorus level on subsequent growth performance, intestinal phosphate transport, and AMPK activity in young broilers.

Zhiqiang Miao,Junzhen Zhang,Jianhui Li,Yu Yang,Guixian Zhang,Carlos M Isales

doi:10.1371/journal.pone.0186828

Abstract

We aimed to determine the effect of low dietary energy on intestinal phosphate transport and the possible underlying mechanism to explain the long-term effects of early dietary energy restriction and non-phytate phosphorus (NPP). A 2 × 3 factorial experiment, consisting of 2 energy levels and 3 NPP levels, was conducted. Broiler growth performance, intestinal morphology in 0–21 days and 22–35 days, type IIb sodium-phosphate co-transporter (NaPi-IIb) mRNA expression, adenylate purine concentrations in the duodenum, and phosphorylated adenosine monophosphate-activated protein kinase (AMPK-α) activity in 0–21 days were determined. The following results were obtained. (1) Low dietary energy (LE) induced a high feed conversion ratio (FCR) and significantly decreased body weight gain in young broilers, but LE induced significantly higher compensatory growth in low NPP (LP) groups than in the high or medium NPP groups (HP and MP). (2) LE decreased the villus height (VH) in the intestine, and LE-HP resulted in the lowest crypt depth (CD) and the highest VH:CD ratio in the initial phase. However, in the later period, the LE-LP group showed an increased VH:CD ratio and decreased CD in the intestine. (3) LE increased ATP synthesis and decreased AMP:ATP ratio in the duodenal mucosa of chickens in 0–21 days, and LP diet increased ATP synthesis and adenylate energy charges but decreased AMP production and AMP:ATP ratio. (4) LE led to weaker AMPK phosphorylation, higher mTOR phosphorylation, and higher NaPi-IIb mRNA expression. Thus, LE and LP in the early growth phase had significant compensatory and interactive effect on later growth and intestinal development in broilers. The effect might be relevant to energy status that LE leads to weaker AMPK phosphorylation, causing a lower inhibitory action toward mTOR phosphorylation. This series of events stimulates NaPi-IIb mRNA expression. Our findings provide a theoretical basis and a new perspective on intestinal phosphate transport regulation, with potential applications in broiler production.

Highlights

Since 1957, selective breeding has significantly increased growth in broiler chickens [1], leading to an increase in leg weakness and incidence of metabolic diseases, such as ascites, sudden death syndrome, and fat deposition [2,3,4,5]
In the medium (MP) and high non-phytate phosphorus (NPP) (HP) dietary groups, Low dietary energy (LE) showed no difference in feed intake (FI) but demonstrated significantly decreased body weight gain (BWG) compared with NE
LE significantly decreased the early Body weight gain (BWG), with no difference in the FI of broilers fed with MP and HP diets; this effect was counteracted by the lack of difference in BWG and final body weight of broilers from the age of 22–35 days

Summary

Introduction

Since 1957, selective breeding has significantly increased growth in broiler chickens [1], leading to an increase in leg weakness and incidence of metabolic diseases, such as ascites, sudden death syndrome, and fat deposition [2,3,4,5]. Quantitative and qualitative feed restrictions in the early growth period were previously used to limit the growth rate and prevent these metabolic diseases [6]. These measures can improve meat quality and enhance resistance to diseases [7]. An increase in the dietary energy level improves the growth rate [9] and increases the phosphorus requirements of chickens [10, 11]. To the best of our knowledge, no study has evaluated the interactive effect of dietary energy and phosphorus, during the early growth period, on later growth performance

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