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The purpose of investigations was to determine, by means of pathomorphological methods, the incidence of different rickets forms and their role for the occurrence of other illnesses in broiler chickens in Bulgaria. Clinical, blood biochemical, gross anatomy and histological investigations were carried out in broiler chickens with signs of rickets. The studies were performed in 12 broiler flocks in 4 farms located in different regions of the country. Based on macro- and microscopic lesions, alterations specific for hypocalcaemic rickets were observed in two farms, whereas signs of hypophosphataemic rickets - in the other two. The rickets diagnosis was confirmed by analysis of blood serum calcium, magnesium and inorganic phosphate concentrations. At the age of 30-35 days, various pathological states were observed in the same farms. The presented results suggested that existing problems in studied flocks were associated with an earlier occurrence of rickets., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Studied were mass disease outbreaks on eight farms in calves intensively fed concentrate mixtures that were rich in phosphorus compounds. Clinically, there were selling and deformations of the joints with pains. The tarsal and carpal joints were chiefly involved. Kyphosis of the backbone, spastic paresis of the posterior part of the body as well as tetaniform spasms in the initial stage of the disease were also observed. Morphologically, the diseased animals manifested erosions and thinning of the joint cartilage, tearing of the Achilles tendon, and increased amounts of the joint fluid. The histologic study revealed edema of the cartilage cells, disorders in the structure of the hyalin cartilage, formation of cavities, and broadening of the lumen of the Haversian canals. In most cases the blood serum presented hyperphosphatemia (up to 15.67 mg% inorganic P) and relative or absolute hypocalcemia (up to 4.47 mg% Ca). On the farm both hypocalcemia and hypophosphatemia were observed. Good prophylactic results were obtained through correct Ca:P ratios in the diet that contained calcium additives as well as by the injection of vitamin D solutions, etc. It is believed that these cases should be referred to a distinctive form of rickets of a characteristic clinical course' the inadequate Ca:P ratios in the rations playing the main etiologic role. Subsidiary causes are probably vitamin D deficiency, restricted movement of the animals, and mechanical traumata caused by the animal's own bodyweight.