The digestibility of grain of two cultivars of oats differing in lignin content

Abstract

A study was conducted to investigate the effect of differences in lignin content in the hulls of oats (Avena sativa L.) on digestion of whole grain by sheep. The in vivo organic matter digestibility of a low-lignin diet based on the cultivar Murray (8 g lignin/kg) was approximately 15% higher than a diet based on high-lignin Mortlock oats (23 g lignin/kg). The digestible energy (DE) values were 15.6 and 14.0 MJ/kg DM for the two diets respectively. The apparent digestibilities of neutral detergent fibre (NDF) and acid detergent fibre (ADF) were 0.63 and 0.57, respectively, in the case of the Murray diet, and 0.31 and 0.28 in the case of the Mortlock diet. Measurements were also made of the rate and extent of dry matter (DM) disappearance of whole grain and hulls from dacron bags suspended in the rumen of a steer for varying lengths of time. There was no significant difference in the loss of Mortlock hull dry matter from bags incubated for 24, 48 or 96 h (mean 5%), compared with Murray (low-lignin) hulls where there was an increase from 8.5% after 24 h to 29.9% disappearance at 96 h. The results are consistent with there being a major effect of hull lignin levels on the digestibility of both hulls and the whole grain and, when hull to groat ratios and hull silica levels are similar, may be the principal factor determining 'nutritional value' of oat grain.