The effect of various levels of calcium, phosphorus and vitamin D in the feed for growing pigs with special reference to atrophic rhinitis.

Thirty-two pigs were divided into 8 groups in an experiment to study the effect of various levels of calcium, phosphorus and vitamin D in the feed on weight gain, feed conversion, calcium, inorganic phosphorus and alkaline phosphatase in serum, ash content of the bones and the health of the pigs. Deficiency of vitamin D caused various degrees of rickets, and some of the animals fed on a diet with a low calcium-phosphorus ratio died in hypocalcemic convulsions. Vitamin D deficiency caused a fall in serum calcium, followed by an increase in alkaline phosphatase. The animals on a diet deficient in vitamin D and with a low calcium-phosphorus ratio had a poorer weight gain, decreased feed conversion efficiency and lower ash content of the bones than the animals on diets with an optimal composition. Various degrees of bone resorption were observed by histological examination of the turbinates from animals on diets with an unfavourable calcium-phosphorus ratio or deficient in vitamin D. The bone resorption was caused by socalled pericytic osteolysis. Signs of osteodystrophia fibrosa were also found. Neither macroscopic nor histological signs of atrophic rhinitis were seen. In some cases of spontaneous atrophic rhinitis from pigs outside the experiment pericytic osteolysis of the turbinates was also shown. It is concluded that this form of bone resorption may occur simultaneously with atrophic rhinitis when the diet is deficient in vitamin D or when the calcium-phosphorus ratio is unfavorable.