Comparison of gravimetric and spectrophotometric lignin quantification methods across sugarcane cultivars and harvest ages

The objective was to evaluate which method for determining lignin is most suitable for characterizing the quality of sugarcane as forage for ruminants. The treatments were lignin quantification using the acid detergent fiber method, lignin quantification using the acetyl bromide cell wall method, and lignin quantification using the acetyl bromide neutral detergent fiber method. The lignin concentration was quantified in samples from four sugarcane cultivars, IAC86-2480, IACSP93-3046, IACSP04-704, and IACSP04-656, at three vegetative growth stages, 365, 420, and 480 days. Whole stalks were harvested, chopped, and sampled. The samples were dried in an oven at 55°C, and the amounts of dry matter, crude protein, mineral matter, ether extract, neutral detergent fiber, acid detergent fiber, cellulose, hemicellulose, and lignin were measured. The factors method, cultivar, and date were analyzed together, and there was no interaction between them ( P = 0.1989), nor was there an interaction between analytical method and cultivar ( P = 0.5153). Lignin at 365 days was 242, 200 and 146 g/100g for acetyl bromide in NDF, acetyl bromide in cell wall and detergent acid lignin method ( P < 0.0001). The spectrophotometric method for quantifying lignin by acetyl bromide performed on neutral detergent fiber was more suitable for discriminating the qualitative value of sugarcane as a roughage for ruminant diets ( in vitro digestibility was 65.46, 63.44, 66.67, and 62.56 g/100g for IAC86-2480, IACSP93-3046, IACSP04-704, and IACSP04-656 respectively) than the methods for measuring lignin by gravimetric procedure in acid detergent fiber or by acetyl bromide determined in the cell wall.