Effect of inert fillers with changing energy-protein ratio on growth performance and energy digestibility in broilers

The purpose of this study was to examine the effects of using sand or diatomaceous earth (DIAE) as an inert filler while changing the energy-to-protein ratio in broilers, and therefore to evaluate if doing either will confound the results in energy enzyme efficacy studies by reducing the difference observed between the standard and low energy control diets. The dietary treatments consisted of one control treatment (3,050 ME kcal/kg, 220 CP g/kg) and a 2 × 2 factorial arrangements with 2 energy-to-protein levels (2,850 ME kcal/kg, 205 CP g/kg or 2,850 ME kcal/kg, 220 CP g/kg) and 2 inert fillers (sand or DIAE), each with 9 replicates. Each replicate pen included 5 straight-run broilers fed for a period of 21 d with weekly pen BW and feed intake measured. Ileal contents were collected on d 21 for ileal digestible energy (IDE), with 0.2% titanium dioxide as an indigestible marker. According to the main effect for inert filler, BW was significantly lower (P < 0.05) in treatments with reduced energy on d 21. Compared with the control group, no differences were observed among the reduced energy treatments for FCR and productivity index. Both IDE and ileal energy digestibility coefficient (IEDC) were decreased in the treatments formulated with reduced energy. Among reduced energy treatments, diets containing sand had significantly higher IDE and IEDC than the ones with DIAE. This study confirms that reduced dietary energy negatively influences broiler performance. Adding sand as the inert filler had an independently beneficial effect, and therefore DIAE may be a more appropriate source of inert filler to replace fat in a diet with a disrupted energy-to-protein ratio, which is the typical methodology in energy enzyme efficacy studies.