MINERAL-COMPOSITION OF TROPICAL FORAGES IN THE MOUNT-ELGON REGION OF KENYA .1. MACROMINERALS

A survey of the micro-mineral concentrations in herbage in the Mt Elgo n region of western Kenya is described. A total of 135 samples of dry- season herbage from 84 farms covering 30 000 km(2) was analysed for ca lcium (Ca), phosphorus (P), magnesium (Mg), and sulphur (S). Mean (+/- standard deviation) concentrations were Ca, 15 (0.52); P, 1.4 (0.76); Mg, 1.6 (0.53); S, 1.5 (0.59) g kg(-1) matter. Calcium, P, and Mg conc entrations were low compared with surveys in other tropical countries may this may partly reflect the mature stage at which herbage was samp led. Comparisons with recent estimates of the mineral requirements of ruminants indicated that most of the samples were deficient in Ca and P while a minority was deficient in Mg and S. However, such deficits a re not synonymous with constraints upon livestock production, and supp lementation trials with grazing livestock should be conducted.