Seasonal and management effects on the composition and availability of herbage, steer diet and live-weight gains in a Themeda triandra grassland in Kenya. I. Methods and study of techniques

Abstract

SUMMARYA 2·year grazing trial was carried out on an equatorial Themeda triandra range grassland in the Rift Valley of Kenya, at 1890 m altitude with a bimodal rainfall of 700 mm p.a., to characterize seasonal changes in the pasture and to determine the influence of climatic and management factors on forage availability and composition, grazing selection and live-weight gains on Boran steers (Bos indicus).Fourteen categories of sampling and measurement techniques used in this work are described and some methodology problems in rangeland evaluation discussed.For precise estimation of herbage yields in large paddocks unacceptably large plotsizes and numbers were required so an arbitrary sample of twelve 10 yd x 1 yd plots per paddock was adopted giving c.v.s of 16–50%. Subsequent sampling was limited to three contrasting treatments in the most uniform block. A ‘forceps point’ method was developed for botanical estimation of oesophageal fistula samples and provisional weight correction factors calculated. In a parallel feeding trial regressions were calculated for relating the chemical composition of oesophageal fistula samples to that of the herbage ingested.