Dry matter,protein, energy and fibre intake by dairy heifers grazing a Rhodes grass (Chloris gayana) pasture

Dry matter (DM), protein, energy and fibre (ADF) intakes of Friesian and Ayrshire dairy heifers grazing a Rhodes grass pasture in Central Kenya were studied by indicator techniques for ten 22-day periods, each comprising 10 preliminary days and 12 collection days.Digestibility coefficients of DM, CP, GE and fibre were higher (P < 0.05) in the wetter periods and generally declined during the drier periods, as pasture matured. Intakes of DM, DCP and DE decreased (P < 0.05) as herbage matured. Average daily intake per kgW^0.75 was 73.9-g DM, 4.1-g DCP, 31.8-g ADF and 167-kcal DE. Average daily gain (ADG) also varied (P < 0.05) with period and was positively related to intake of digestible dry matter, protein and energy. When conditions were wet, ADG was satisfactory at 480 g. In dry conditions, the heifers ingested 26.1-g DDM, 1.6-g DCP and 110-Kcal DE per kgW^0.75 daily and gained at 200 g/day, and supplementation was deemed necessary to sustain an optimum ADG of 550 g. The factors which may have limited pasture intake by the grazing heifers are discussed. In general, a Chloris gayana pasture, grazed at an appropriate stocking-rate, will meet the requirements of dairy heifers for maintenance and, to a variable degree, those for growth in areas of Kenya with an annual rainfall of 1400 mm and with a high potential for increased cattle production.