Published in Scientific Works. Series C. Veterinary Medicine, Vol. 19 ISSUE 4
Written by EFFECT OF VARIOUS LEVELS OF DIETARY CALCIUM ON BLOOD CALCIUM CONCENTRATION AND HORMONAL STATUS IN WHITE CORNISH AND WHITE LEGHORN HENS
Two hen breeds, White Cornish (COR) and White Leghorn (LEG) 34-week-aged were used in this experiment. The basic diet of these hens contained 3.8% Ca. This diet was supplemented for an experimental period of 8 days with 0.0, 1.0 and 2.0 and, respectively, 3.0% calcium. During the experimental period the plasma blood levels of Ca, phosphorus, parathormone, calcitonin, vitamin D and estradiol were monitored. The results relive a significant increase of the blood plasma levels of Ca and phosphorus in both COR and LEG hens beginning form the 2% calcium dietary supplementation. Phosphorus levels increased too, but the Ca/P ratio indicated an imbalance for the calcium. In the same time it was found a significant decrease of the plasma level of parathormone in both 2% and 3% Ca supplemented CRG and LEG hens. Blood plasma level of calcitonin doesn’t follow a clear increasing in any experimental group, neither for CRH nor for LEG hens: statistical analyses between day one and 8th day of the experimental periods didn’t relive any statistical significant difference in any experimental group for this hormone. Plasma vitamin D concentrations followed a statistical significant (P<0.05) increase for both 2% and 3% calcium supplemented diets in both CRN and LEG hens. Estrogen levels were found significantly elevated in LEG hens vs. CRH hens, but the differences were not in relation to the blood calcium concentrations. In conclusion, blood calcium levels in hens influences the parathormone and vitamin D secretions but its excact influence on the calcitonin and estrogens is not clear. Further experiments are recommended to find the exact mechanisms of blood calcium regulation in birds.
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