The neutral detergent fiber degradability (NDFd) of sugar-cane, and elephantgrass, corn, and sorghum silages were predicted by in situ method, with different time points, sample grind sizes (1 and 2mm) and animal species (sheep and cattle). The feedstuffs were incubated at 3, 6, 12, 24, 36, 48, 72, 96, 120, 144, 240 hours. The effects of sample grind sizes and of the species in NDFd were analyzed through the test of identity of non-linear regression models and interpreted by factor analysis. The rates of degradation of NDF (k d) were also estimated for two times of incubation in situ (times 6 and 24h or 6 and 36h), and they were compared to the k d values estimated at the in situ trial, through the t statistical test. The k d values estimated by different time points and predicted by in situ incubation times were similar (P>0.05). There is little interference of particle size in degradation parameters, and the NDF degradation in situ trials in sheep can not be used as an experimental model for cattle.
sheep; degradability; neutral detergent fiber
