Response evaluation of broiler chickens to different dietary calcium-to-phosphorus ratios: Effect on growth performance, nutrients retention and intestinal morphology

Abstract

Importance of the work: Calcium (Ca) and available phosphorus (AvP) are necessary minerals that have important roles in the animals; however, increasing dietary calcium causes several health problems.
Objectives: To evaluate the effect in broiler chickens of Ca:AvP ratios on the productive performance and the retention of nutrients.
Materials & Methods: In total, 360 Ross 308 broilers aged 11d (mean initial body weight ± SD = 249.80 ± 10.45 g) were randomly allocated to six dietary treatments with six replicates for each treatment and 10 birds per replicate. The experimental diets contained six concentrations of calcium (1.4%, 1.2%, 1%, 0.8%, 0.6% or 0.4%) and one level of phosphorus (0.4%) that were used to form six calcium-to-phosphorus ratios (3.5:1, 3:1, 2.5:1, 2:1, 1.5:1 and 1:1, respectively).
Results: The Ca:AvP ratio had a significant (p < 0.001) effect on body weight and weight gain. The feed intake was reduced (p = 0.002) for high Ca:AvP ratios (3.5:1 and 3:1) compared to the standard Ca:AvP ratio (2:1) during the grower period but this effect disappeared in later periods. The feed conversion ratio was significantly (p = 0.001) improved in birds fed the standard Ca:AvP ratio (2:1) compared to the other ratios. The production index was the highest (p < 0.001) in birds fed the standard Ca:P ratio compared to those fed other unbalanced ratios. The different Ca:AvP ratios had no significant (p < 0.05) effect on mortality percentage. The nutrients retention and jejunum morphology were impaired with high Ca:AvP ratios (3.5:1 and 3:1) compared to several other ratios (2:1, 1.5:1 and 1:1).
Main finding: These results suggested that 2:1 was the best ratio between calcium and phosphorus to achieve optimum growth performance.