Phosphorus and the grazing ruminant. 4. Blood and faecal grab samples as indicators of the P status of cattle

Abstract

Blood plasma and faecal grab samples were evaluated as indicators of P status of cattle grazing at two experimental sites (Glen and Armoedsvlakte). Plasma Pj levels clearly identified the P cattle at Armoedsvlakte as being P deficient whilst at Glen the P group tended towards lower levels than the supplemented cattle although differences between them were seldom significant. Plasma levels well below the critical range (2 mg/100 ml plasma) can be useful for identifying a P deficiency but higher levels seem insensitive for distinguishing between groups, as was often observed at Glen. Faecal P levels tended to rank the groups according to their respective intake of P. Poor feed intake of P cattle at Armoedsvlakte depressed faecal output severely; analysis of grab samples for analysis of percentage P may lead to erroneous conclusions regarding P status. Under these circumstances it would seem advisable rather to determine total P excretion via the faeces to differentiate between the two groups. S. Afr. J. Anim. Sei. 1986, 16: 18-22