Abstract
The apparent calcium (Ca) digestibility coefficient (ADC) and true digestibility coefficient (TDC) of different inorganic calcium sources were determined in laying hens of different ages. Three Ca digestibility tests were carried out, each assessing 240 Lohmann Brown lineage laying hens distributed in a completely randomized design. Nine dietary treatments were arranged in a 3 × 3 factorial design consisting of three ages (40, 50 and 70 weeks) × three Ca (dicalcium phosphate (DCP) sources, fine (FL) and coarse (CL)) limestone, comprising eight replicates per treatment of six birds per experimental unit. Regarding the DCP, the ADC was higher (P as 0.889, 0.613 and 0.712, respectively. No effect (P > 0.05) of age on the ADC was noted for either FL or CL. Comparing Ca sources, DCP exhibited a higher (P 0.05). Endogenous loss values of 790, 860 and 930 mg·kg-1 of consumed dry matter were observed at 40, 50 and 70 weeks, respectively. For the TDC, no interaction (P > 0.05) was observed between Ca sources and bird age. The highest TDC value (P > 0.05) was found in birds fed DCP (0.786) followed by FL (0.637) and CL (0.534). In addition, birds at 40 weeks of age (0.714) exhibited higher TDC values (P
Highlights
The main inorganic calcium (Ca) sources used in bird diets are calcitic limestone and calcium phosphates, which exhibit variable Ca bioavailability [1]
The apparent calcium (Ca) digestibility coefficient (ADC) and true digestibility coefficient (TDC) of different inorganic calcium sources were determined in laying hens of different ages
Nine dietary treatments were arranged in a 3 × 3 factorial design consisting of three ages (40, 50 and 70 weeks) × three Ca (dicalcium phosphate (DCP) sources, fine (FL) and coarse (CL)) limestone, comprising eight replicates per treatment of six birds per experimental unit
Summary
The main inorganic calcium (Ca) sources used in bird diets are calcitic limestone and calcium phosphates, which exhibit variable Ca bioavailability [1]. The determination of Ca digestibility in these sources has received little attention, mainly due to their low cost, abundant availability and surplus global reserves [2] [3]. According to Albino et al [5], older laying hens exhibited a 20% reduction in intestinal Ca absorption, increasing bone Ca mobilization and reducing carbonic anhydrase activity, leading to lower eggshell calcification. Zhang and Coon [9] reported that laying hens displayed the ability to maintain larger food particles in their gizzards for longer periods of time, increasing solubility and in vivo use. Limestone particle size influences in vitro solubility [9] [10] [11] and a negative correlation between in vitro and in vivo Ca solubility in laying hens has been noted [9] [12]
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