Effects of feeding varying levels of protein and phosphorus in relation to bone disorders in cattle

Abstract

Steers were fed low or high protein diets with varying levels of phosphorus. Two steers on the low protein diet developed a disorder which clinically resembled osteomalacia after 21 weeks of experimental feeding, and other animals on the same diet showed varying degrees of lameness. The total fresh weight, total mineral content, and the calcium and phosphorus levels of the metacarpal bones were significantly lower in the low protein group. Total fresh weight, total ash content of the rib bones was also lower although there were no differences between groups in the calcium and phosphorus content of rib bones. There were significant differences between treatment groups in blood levels of calcium, phosphorus and protein. The carcase weight of high protein animals was significantly greater than that of the low protein animals. Phosphorus level in the diet had little effect on any tissue measurement. The results showed that a bone disorder could develop in animals fed adequate phosphorus but inadequate protein. The implications of the experiment are considered in relation to the levels of protein and phosphorus in pasture throughout northern Australia.