Effects of partial replacement of conventional limestone with dietary micro-calcium carbonate on performance, egg quality, hematology, and calcium metabolism of laying hens during peak production

Abstract

The present study was conducted to evaluate the effects of limestone replacement with dietary micro-calcium carbonate (MCC) on performance, egg quality, and serum Ca metabolism in peak-phase laying hens. A total of 120 laying hens (30 wk of age) were assigned to 1 control or 4 treatment groups for 8 weeks. Half of the total limestone was replaced by calcite in different particle sizes in the treatment groups (1, 20, 40, and 100 µm) and by fine limestone (~2 mm) in control. During the experiment, egg production and mass decreased (p < 0.05); however, eggshell thickness increased in hens fed with calcite groups compared to the control fed birds. There was a contrast between control vs. treatment, and a negative linear trend (p = 0.11) with the particle sizes for feed conversion ratio (FCR) was recorded. The different particle size of calcite had no effect on feed consumption, egg quality parameters, and hematology parameters of serum. However, the serum calcium (p = 0.01) and vitamin D (p < 0.0001) levels were affected by calcite, serum parathyroid hormone, calcitonin, phosphorus levels, and Ca:P ratio were not affected. The effects of dietary calcite sources may differ from conventional or nano-sized calcium carbonate sources in laying hens, especially for Vit D metabolism.