Published in Scientific Works. Series C. Veterinary Medicine, Vol. 19 ISSUE 3
Written by EVOLUTION OF HORMONAL CONTROL OF CALCIUM AND PHOSPHORUS METABOLISM IN HENS ACCORDING TO AGE AND EGG PRODUCTION
The aim of this work was to determine the relationship between the calcium and phosphorus metabolism and the levels of the main hormones involved in their blood regulation in laying hen. Two breeds of hens were used in this work, 22 weeks aged each one: White Cornish (CRN), as a breed of low egg production and White Leghorn (LGH), as a breed of higher egg production. The hens were raised in industrial system and they were fed according to the technologic diets. The hens were monitored from 22 to 44 weeks of age for the evolution of the parathormone, vitamin D, calcium and phosphorus levels in the blood plasma. Blood glucose concentration, total lipid, total proteins, albumins, globulins, creatinine, and uric acid were also monitored. Analysis of the hormone evolution relieves a peak of the PTH level in LGH hens, around 30 weeks of age (amounted to 392 pg/mL vs. 198 pg/mL in CRN hens). This peak of PTH is behind the laying peak and it is significantly higher in LGH hens vs. CRN hens. It was remarked that the LGH hens reached the peak of the PTH one week sooner vs. CRN hens. Regarding vitamin D, its plasma level presented a relatively constant evolution in CRN, while in LGH it presented an increase around 30 – 32 weeks-of-age up to 142 pg/mL, then it decreased slowly. Accordingly, in LGH hens, the level of calcium (in mg/dL) raised from 9.9 at the beginning of the laying cycle to 34.4 in the peak of the laying, decreasing then, to 18.0 toward the end of the monitoring period. In CRN hens, at the same age, the values of the plasmatic calcium were: 6.2, 12.9 and 18.0, respectively. The calcium/phosphorus ratio presented an ascendant evolution in both, LGH and CRN breeds, indicating an increasing of the free calcium content of the blood plasma. Plasma albumins ranged between 16.0 and 20.0 mg / mL in the LGH hens and between 19.8 and 22.8 mg / mL in the CRN hens. Uric acid plasma levels have evolved relatively parallel to the laying percentage, showing an intensified protein catabolism, according to laying percentage, in LGH hens. Total lipids followed an ascending evolution up to the peak of the laying, and then they decreased slowly in both low and high production breeds.
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