Calcium homeostasis in the laying hen. 1. Age and dietary calcium effects

• Published in: Poultry science Vol. 73; no. 10; pp. 1581 - 1589
• Main Authors: Elaroussi, M.A. (University of Missouri, Columbia, MO.), Forte, L.R, Eber, S.L, Biellier, H.V
• Format: Journal Article
• Language: English
• Published: England 01.10.1994
• Subjects: ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; AGE; Age Factors; ALIMENTACION DE LOS ANIMALES; ALIMENTATION DES ANIMAUX; Animals; Bone Density; CALCIO; CALCIUM; Calcium - blood; Calcium - metabolism; Calcium, Dietary - administration & dosage; CARENCE MINERALE; CENDRE; CENIZA; Chickens - metabolism; Cholestanetriol 26-Monooxygenase; DEFICIENCIA DE MINERALES; EDAD; Female; FEMELLE; HEMBRA; HOMEOSTASIE; HOMEOSTASIS; Homeostasis - physiology; HUESOS; HUESOS DE LOS MIEMBROS; Kidney - anatomy & histology; METABOLISME DES MINERAUX; METABOLISMO DE MINERALES; Organ Size; OS DES MEMBRES; OXIDORREDUCTASAS; OXYDOREDUCTASE; Parathyroid Hormone - metabolism; PESO; Phosphorus - blood; POIDS; POLLO; POULET; REIN; RESISTANCE MECANIQUE; RESISTENCIA MECANICA; RINONES; Steroid Hydroxylases - metabolism
• ISSN: 0032-5791; 1525-3171
• DOI: 10.3382/ps.0731581

An experiment was carried out to investigate the effects of age of laying hens (young = 22 wk vs old = 120 wk) in maintaining Ca homeostasis during periods of Ca depletion then repletion with Ca. Plasma Ca and P, tibia breaking strength and percentage ash, renal 25-hydroxycholecalciferol-1-hydroxylase (1 alpha-hydroxylase), and parathyroid hormone (PTH)-stimulated adenylate cyclase activities were studied during 28 d of Ca depletion on a.08% Ca diet (LC) and 28 d of Ca repletion on a 3.75% Ca diet (HC). When laying hens on a HC diet were placed on a LC diet, plasma Ca and P, tibia breaking strength and ash percentage, and renal PTH-dependent adenylate cyclase activity were significantly depressed, but renal 1 alpha-hydroxylase activity was significantly stimulated. These changes were greater in the young hens than in the older hens; therefore an interaction between age and dietary Ca was found. These changes were of a lesser magnitude at 28 d of Ca depletion, probably due to the cessation of egg laying and to the desensitization of hormone-mediated function. 1 alpha-Hydroxylase activity was significantly less during the repletion period. The age effect was most pronounced for 1 alpha-hydroxylase, with the younger birds expressing significantly higher activity and ability to respond to hypocalcemia. There was a significant increase in kidney weights in Ca-deficient groups at 14 and 28 d of Ca depletion. It is concluded that younger hens have greater adaptive responses to Ca restriction than do older hens