Effects of regrowth period, season and harvesting frequency on the yield and nutritive value of Chloris gayana in the southern highlands of Tanzania

Abstract

Two experiments were conducted in the Makambako division of the southern highlands of Tanzania to investigate the effects of regrowth period, season and harvesting frequency on the yield and nutritive value of Chloris gayana. The first experiment was conducted in 2002 in a 4×2 factorial arrangement in a complete randomised block design with six replications. The treatments were period of regrowth (three, six, nine and 12 weeks) and season (early wet season January–March and late wet season April–June). The second experiment was conducted in 2003 in a complete randomised design with six replications. The treatments were four cutting frequencies (three, six, nine and 12 weeks). In Experiment 1, the dry matter yield (DMY) ranged from 1.09–7.99t ha−1 and from 0.97–3.53t ha−1 (P < 0.05), while the crude protein (CP) content ranged from 13.9–8.25% and 16.09–9.85% (P < 0.05) in the early and late wet seasons, respectively. In vitro dry matter digestibility (IVDMD) and metabolisable energy (ME) declined faster with increasing periods of growth in the early than in the late wet season. ME ranged from 9.21–7.29MJ kg−1 DM (P < 0.05) and 8.02–7.87MJ kg−1 DM (P > 0.05) in the early and late wet seasons, respectively. For Experiment 2, the nine- and 12-week cutting frequencies did not differ (P > 0.05) in terms of cumulative DMY (19.07 versus 18.93t ha−1) but produced nearly twice as much as the three- and six- week cutting frequencies (10.18 and 8.32t ha−1). CP, IVDMD and ME decreased while neutral detergent fibre (NDF) increased with decreased cutting frequency. The results of the present study suggest that the optimal balance of dry matter yield and nutritive value of C. gayana at Makambako is reached at the ninth week of regrowth. Regardless of season, dairy farmers in this area who are feeding pure C. gayana must provide energy supplement to their dairy cows.