Herbage biomass production and nutritive value of mulberry (Morus alba) and Calliandra calothyrsus harvested at different cutting frequencies

Effects of cutting frequencies on herbage biomass production and nutritive value of Morus alba and Calliandra calothyrsus were investigated. Forage regrowth was harvested at frequencies of 1, 2, 4 and 6 months which constituted the four treatments. Degradabilities, to establish nutritive values, were measured at 0, 3, 6, 12, 24, 48, 72, 96 and 120 h of rumen incubation by a nylon bag technique using three rumen fistulated steers. Crude protein (CP) of M. alba declined linearly (P<0.05) from 234.4 to 169.3 g/kg DM as it matured from 1 to 6 months, while in C. calothyrsus CP decreased (P<0.05) at a decreasing rate from 232.7 to 156.0 g/kg DM with increasing maturity. Neutral detergent fibre (NDF) and acid detergent lignin increased (P<0.05) with increasing maturity. C. calothysus and M. alba leaf:stem ratio decreased from 3.3 to 0.4 and 2.9 to 0.7, respectively, with increasing maturity. While C. calothyrsus had the highest total herbage biomass yield of 45.9 t/(ha yr−1) at the 4 months cutting frequency, M. alba had yields of 18.6 and 18.4 t/(ha yr−1) at 2 and 6 months, respectively. Highest (P<0.05) effective CP degradability of 901.3 g/kg CP occurred in M. alba at a cutting frequency of 1 month while in C. calothyrsus the highest (P<0.05) value was 492.8 g/kg CP at 2 months. Consequently, in all treatments, rumen degradable CP (RDP) was consistently higher in M. alba (96.5–199.2 g/kg CP) than in C. calothyrsus (52.5–105.2 g/kg CP) but decreased (P<0.05) with increasing maturity. Digestible undegradable CP (DUP) was affected (P<0.05) by increasing maturity, but was lower in M. alba compared to C. calothyrsus. Although C. calothyrsus was superior to M. alba in annual herbage biomass production and DUP, it had lower RDP than M. alba and the nutritional value of both greatly depends on maturity and leaf:stem ratio. Cutting management options that involve harvesting C. calothyrsus and M. alba at maturities between 2 and 4 months, when leaf:stem ratio is greater than 1.0, is crucial in making a decision when to harvest fodder of high nutritional value. This suggests that smallholder farmers in Uganda can efficiently use M. alba and C. calothyrsus in rations to improve dairy cattle productivity, if harvested at maturities between 2 and 4 months.