Optimal harvest age for napier grass (Pennisetum purpureum Schum.) during the rainy season based on yield and nutritional value

摘要

A continuous in vivo digestibility trial was done to measure the effects of ten regrowth ages (18, 25, 32, 39, 46, 53, 60, 67, 74 and 81 d) on forage yield, chemical composition, nutrient digestibility, energy density and optimal harvest age in napiergrass, using energy and digestible protein production per hectare as the main variables. Experimental period was the rainy season and study area was Bayamo, Cuba. Four mature Pelibuey sheep wethers in metabolism cages were fed fresh forage twice daily under a completely randomized design. As regrowth age increased, biomass per hectare increased (up to 2.58 t/cut) and nutrient contents decreased. Crude protein decreased from over 14 % at 18 d to almost 6 % at 81 d, in contrast to progressive increases in dry matter (14 to 18 %) and crude fiber (30 to 38 %). With increasing regrowth age, linear reductions were observed in nutrient digestibility coefficients and estimated metabolizable energy (9.54 to 5.86 MJ/kg DM). Based on a combination of energy anddigestible protein yield per hectare, recommended harvest age under the studied conditions is within an interval of 54 and 60 d of regrowth.