Phosphorus and the grazing ruminant. 1. The effect of supplementary P on sheep at Armoedsvlakte

Abstract

The performance in terms of bodymass and reproduction of two groups of free-grazing Dorper ewes, with (+ P) and without (- P) phosphorus (P) supplementation, was investigated over 4,5 years at Armoedsvlakte (notorious for its P-deficient soils) to establish whether sheep are as susceptible to a P deficiency as cattle. The P status was monitored in blood and rib bone samples, taken at different stages of the reproductive cycle. Effects of feed intake on bodymass of both groups are discussed; the mass of - P ewes was 9,6% less than the + P group. The only effect on reproductive performance was that the + P group tended to wean heavier lambs. Levels of P in rib bone samples clearly indicated cyclic changes in the P reserves, associated with changes in physiological status. Bone P levels successfully identified the - P ewes as being deficient in P.