Effects of food deprivation and particle size of ground wheat on digestibility of food components in broilers fed on a pelleted diet

Abstract

1. The first aim of the experiment was to study the effect of wheat (Triticum aestivum) particle size on the digestibility of starch in a pelleted diet given to broilers. The second aim was to study the consequences of food deprivation before the excreta collection period (from 21 to 24 d). Wheat from a strong hardness cultivar was incorporated at 546·1 g/kg in diets. The other main ingredients were soybean meal (353·5 g/kg) and rapeseed oil (55·0 g/kg). Diets were given as pellets. The experimental design was a 2 × 2 factorial design testing two particle sizes of wheat flour and two procedures of a balance experiment (with or without food deprivation).

2. Birds given diet C (wheat coarse grinding before pelleting) had significantly greater gizzard weight than birds fed on diet F (wheat fine grinding before pelleting).

3. Starch digestibility value was significantly increased when birds were fed on diet F. This effect was halved by food deprivation. No significant effect of grain particle size was observed for protein and lipid digestibility values. However, food deprivation decreased apparent protein digestibility, with an effect which was more pronounced for fine than for coarse grinding.

4. AME_N of the diet was significantly improved by fine grinding of wheat and decreased by food deprivation. However, no significant differences in growth performance were induced by differences in wheat grinding.

5. No significant effect of grinding was observed on the water excretion:feed intake ratio. No significant difference was observed for vent score between treatments.

6. There was over-excretion of starch in the first hours of refeeding following food deprivation.

Acknowledgements

The authors thank Mr P. Colace (Tecaliman, Nantes, France) for help in the grinding process, Mr K. Gérard (INRA, Nouzilly, France) for helpful assistance in the management of experimental birds, and Mr L. Bonnal for NIR measurements (CIRAD-EMVT, Montpellier, France).