Estimation of in vitro digestibility and fermentation of elephant grass by near infrared spectroscopy

Abstract

The methods used to evaluate kinetic parameters of ruminant feeds can be in situ and in vitro. For both methods, it is necessary to maintain cannulated animals in order to collect the inoculum from the rumen, which has been under strong pressure from society, in terms of animal welfare policies, to avoid this type of practices. This work aimed to evaluate the estimation of in vitro digestibility and fermentation of elephant grass forage by near infrared reflectance spectroscopy (NIRS), as a fast and noninvasive alternative to the in vitro method. The experimental design was in randomized blocks with three repetitions. The treatments were arranged in a split-plot scheme, with 13 genotypes in the plot and 15 regrowth ages in the subplot. Crude protein (CP) and neutral detergent fiber (NDF) contents; in vitro dry matter (IVDMD) and NDF (IVNDFD) digestibilities; and total volume (V_t), gas production rate (μ) and half-life conventional analyses were determined for pre-dried elephant grass forage samples. For the evaluation of NIRS models performance, coefficient of determination (R²cv) and standard error of cross validation (SECV) were used. As the regrowth age advanced, there was a linear increase in the NDF content and a linear reduction in the IVDMD, IVNDFD and V_t values. The NIRS estimates proved to be adequate for IVDMD (R²cv = .95), IVNDFD (R²cv = .85), V_t (R²cv = .81) and gas production at 48 (R²cv = .82), 72 (R²cv = .85) and 96 h (R²cv = .84), confirming as an alternative to the in vitro methods that dispense with the use of cannulated animals.