The Effect of Experimental Vitamin D administering on the Calcium Metabolism in Adult Laying Hens

Nicolae DOJANA, Claudia PREDA, Rosalie BALACEANU


Abstract. The researches were performed on four groups of 34-week-age hens: a control group and three experimental groups treated with three levels of i.m. injected vitamin D2 in doses (in IU/k.b.w: 20,000, 100,000 and respectively, 200,000, for 10 days. The results showed that vitamin D2 treatement had a significant effect on egg shell dry matter (DM) weights: mean values were 5.89 g/egg shell in control and 5.86, 6.35 and, respectively, 6.30 g DM in the three treated groups. Egg shell thickness was about 8% higher in experimental groups vs. control, the percentage being higher in the groups that received higher vitamin D doses. The maximal amount of calcium removed by egg shell was 21% higher in vitamin D injected hens vs. control (P=0.0029). Mean tibia mineral content was 68 mg ash /g bone higher in the three experimental groups vs. control. At the end of the experimental period, blood plasma calcium showed higher values vs. control (P=0.0098). Calcium removed by faeces as unabsorbed or excreted in urine was significantly lower vs. control (P=0.0074). It was found that the largest amount of ingested calcium was lost through faeces, as unabsorbed or excreted calcium. Calcidiol/calcitriol ratios ranged between 0.75 and 1.52 in the experimental groups vs. 0.40 in control. In conclusion, ascending doses of vitamin D in laying herns improve the calcium absorption during the peak of the laying cycle, increase the plasma calcium levels, the content of egg shell calcium and bone mineral content but the main ingested calcium remains lost by faeces, The effects are not proportional with the vitamin D doses.



adult laying hens, vitamin D, calcium metabolism

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