The role of the ultimobranchial glands in calcium metabolism of the laying hen

An experiment was conducted in two trials involving 113 Single Comb White Leghorn pullets to study the effect of ultimobranchialectomy and confinement on calcium metabolism of the laying hens. Ultimobranchialectomy and sham operations were performed on chicks at one week of age. They were then reared to maturity in floor pens and housed through the laying period in 6 x 8 and 10 x 16 inch cages and in floor pens. In trial 1, ultimobranchialectomy combined with stress of confinement resulted in a significant reduction in bone density. In addition, it also resulted in significant increases in weights of the thyroid and adrenal glands. In trial 2, however, the operation resulted in no significant decrease in bone density but did result in nonsignificant increases in the weights of the thyroid or the adrenal glands. In trial 1, ultimobranchialectomy combined with the stress of confinement in cages resulted in a nonsignificant reduction in bone breaking strength; whereas, in trial 2, a significant reduction was found as a result of the operation combined with the stress of confinement. In both trials, the response of the ultimobranchialectomized (UBX) pullets to bovine parathyroid extract as measured by serum calcium level Was found to be greater as compared to the sham operated controls. Ultimobranchialectomy resulted in a nonsignificant increase in the incidence of cage layer fatigue. In addition, the operation resulted in nonsignificant increases in specific gravity scores of eggs, parathyroid weights, serum calcium, and hematocrit values. Confinement of pullets to laying cages resulted in a significant decrease in bone density and bone breaking strength in one of the two trials. In both trials, confinement of laying pullets to small cages resulted in significant changes in the ultimobranchial glands of these birds which were: (1) increased weight, (2) hypertrophy of cells, and (3) a decrease in calcitonin content.