Nutritive value of danish-grown barley varieties, II, effect of carbohydrate composition on digestibility of energy and protein

Abstract

The nutritive value of nine barley varieties grown in three successive years on good quality clay soil and poor quality sandy soil were investigated. The barleys were subdivided into four spring feeding, three spring malting and two winter feeding varieties. Digestible energy (DE), true protein digestibility (TD), biological value (BV) and net protein utilisation (NPU) were determined in rats. DE was 1·3 % higher in spring malting compared to spring feeding varieties. The higher DE was accounted for by a higher starch and lower dietary fibre (DF) content. For all barleys DE varied from 73·1 to 83·1 %. This variation was attributed to the composition of the carbohydrate fraction. Dietary starch was positively correlated and total and insoluble DF (IDF) negatively correlated with DE content. The reason for the strong negative correlation with IDF to DE was that IDF accounts for most of the grain cellulose, hemicellulose and lignin. These DF constituents are highly resistant to microbial degradation. In contrast, neither β-glucan nor SDF had any impact on DE. TD was affected by year and type of barley variety and BV by type of barley variety. However, the variation in TD was not correlated with any of the DF constituents. It is concluded that more detailed carbohydrate analyses would be informative in the estimation of metabolisable or net energy of feed and foodstuffs from chemical data.