Effects of cladode age on biomass yield and nutritional value of intensively produced spineless cactus for ruminants
A randomized complete block design with five replications was used to assess biomass yield, in vitro dry matter digestibility (IVDMD) and nutritional value of spineless cactus (Opuntia ficus-indica) produced under drip irrigation and fertilization. Cladodes were harvested from an established plantation at 30, 37, 45, 60, 75 and 90 d of growth. Weight per cladode increased linearly and length increased quadratically with maturity. Biomass yield (t/ha), gross energy (GE), dry matter (DM), crude protein (CP), neutral detergent fibre and acid detergent fibre increased quadratically with maturity. Thus, the curve became asymptotic at 60 d of growth (28.9 ± 2.1 cm). As growth progressed, concentration of CP and nitrates decreased, and that of fibre increased. In vitro solubility, potential digestibility and digestibility rate of DM decreased linearly with increased maturity of the cladodes. However, there was a quadratic effect of maturity on total digestibility of DM. Thus, the curve became asymptote at 75 d. The optimal yield of nutrients, nutritional value and IVDMD of cladodes were recorded between 60 and 75 d of age when they were 29 to 31 cm in length.
Keywords: Biomass yield, chemical composition, digestibility, maturity, spineless cactus