Abstract
Calcium (Ca) is required for normal growth and is involved in cellular physiology, signal transduction, and bone mineralization. In humans, inadequate Ca intake causes hypocalcaemia, and excessive Ca intake causes hypercalcemia. In chicken, Ca is also required for body weight gain and eggshell formation. However, transcriptomic responses to low/high Ca intake, and mechanisms affecting body weight have not been explored. In this study, we performed comparative RNA sequencing (RNA-seq) using the kidney of broiler chickens fed diets containing 0.8, 1.0, and 1.2% Ca. Annotation of RNA-seq data revealed a significant number of differentially expressed genes (DEGs) in the kidney via pairwise comparison using Cufflinks and edgeR. Using edgeR, we identified 12 DEGs; seven overlapped with those found by cufflinks. Seven DEGs were validated by real-time quantitative-PCR (qRT-PCR) in Ca-supplemented kidneys, and the results correlated with the RNA-seq data. DEGs identified by cufflinks/edgeR were subjected to pathway enrichment, protein/protein interaction, and co-occurrence analyses to determine their involvement in disease. The National Research Council (NRC) recommended Ca intake for 21-day post-hatch broilers is about 1.0%. Our findings suggest that higher-than-recommended Ca intake (1.2%) could reduce body weight gain in broilers, and that affected DEGs are related to stress-induced diseases, such as hypertension.
Highlights
Calcium (Ca) is an essential mineral required for normal cellular physiology and signal transduction in organisms
At the end of the experiment (21-days post-hatch), chickens fed diets containing 0.8% Ca showed the greatest performance for initial body weight (BW), body weight gain (BWG), feed intake (FI), and feed efficiency (FE) (P < 0.01) followed by the chickens fed diets containing 1.0% Ca (P value < 0.01)
We suggest that the linear increase in fatty acid-binding protein 4 (FABP4) and LECT2 expression with increasing Ca concentrations in broiler kidney could lead to more T-cells being activated, stimulate Ca-dependent mechanisms, exhibit a protective effect in tumourigenesis, and directly induce hypertension
Summary
Calcium (Ca) is an essential mineral required for normal cellular physiology and signal transduction in organisms. P-value parathyroid gland increases the blood Ca level through resorption of Ca from bone, absorption of Ca in the intestine, and reabsorption of Ca in the kidney. A few studies have suggested that decreasing the Ca level in diets may improve the growth performance of broiler chickens[15,16]. This beneficial effect is associated with increased inherent phosphorus (P) utilization through the reduction of Ca phosphate formation in the intestinal tract[17], and decreased pH of the intestinal tract, which favours digestive enzyme activity through a reduction of buffering capacity[18]. Pathway analysis, interaction analysis, and co-occurrence analysis, identified DEGs related to reduced weight gain, and identified that oxidative stress, such as hypertension, is associated with the reduced weight gain
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