Bone characteristics, pre-caecal phytate degradation, mineral digestibility and tissue expression were marginally affected by zinc level and source in phytase-supplemented diets in 21-day-old broiler chickens

ABSTRACT

1. This study determined the effect of dietary Zn concentration and source in phytase-supplemented diets on bone mineralisation, gastrointestinal phytate breakdown, mRNA-level gene expression (in jejunum, liver and Pectoralis major muscle) and growth performance in broiler chickens.

2. Male Cobb 500 broilers were housed in floor pens (d 0-d 21) to test seven treatments with six replicate pens (12 birds per pen). Diets were arranged in a 2 × 3 + 1-factorial arrangement. The experimental factors were Zn source (Zn-oxide (ZnO) or Zn-glycinate (ZnGly) and Zn supplementation level (10, 30 or 50 mg/kg of diet). A maize-soybean meal-based diet without supplementation and formulated to contain 28 mg Zn/kg (analysed to be 35 mg Zn/kg), served as a control.

3. Zinc source and level did not influence (p > 0.05) bone ash concentration and quantity or mineral concentrations in bone ash. Tibia thickness was greater in the treatment ZnO10 than in the treatments ZnO30 and ZnGly50 (Zn level × Zn source: p = 0.036), but width and breaking strength were not affected.

4. Pre-caecal P digestibility and concentrations of phytate breakdown products in the ileum, except for InsP₅, were not affected by Zn source or level. Only the expression of EIF4EBP1 (eukaryotic translation initiation factor 4E-binding protein 1) and FBXO32 (F-box only protein 32) in Pectoralis major muscle was affected by source, where expression was increased in ZnO compared to ZnGly diets (p < 0.05).

5. In conclusion, Zn level and source did not affect gastrointestinal phytate degradation and bone mineralisation in phytase-supplemented diets. The intrinsic Zn concentration appeared to be sufficient for maximum bone Zn deposition under the conditions of the present study but requires validation in longer-term trials.

KEYWORDS:

• Zinc
• inorganic
• organic
• broiler
• tibia
• phytase

Acknowledgments

The authors gratefully acknowledge the assistance of Lindsey Rackett, Derell Hardman, Shravani Veluri, Mohammad Pilevar, Adeleye Ajao, Iyabo Oluseyifunmi and Bhargavi Kasireddy with animal care and chemical analyses. The authors also thank the laboratory team of the Animal Nutrition Department for the analysis of inositol phosphates and myo-inositol.

Disclosure statement

Alessandra Monteiro is an employee of Animine (France). The authors declare no conflict of interest.

Data availability statement

The data supporting the findings of this study are available from the corresponding author, O.A.O., upon reasonable request.

Additional information

Funding

This study was funded by Animine (Annecy, France).