ALBERT

Description: Leaves of 12 accessions of Brachiaria sp. (three accessions from each of four species) were subjected to tests of shearing strength using a Warner Bratzler meat shear. Morphological measurements of these leaves were also taken in an attempt to standardize shearing strength measurements per unit of leaf tissue. The technique was evaluated for its capacity to detect differences between accessions of the same species. All samples were also analysed for dry matter (DM), organic matter (OM), neutral detergent fibre (NDF), acid detergent fibre (ADF), lignin, crude protein, silica and digestibility in order to relate measures of physical strength to chemical components. Results demonstrated the presence of a clear relationship between shearing strength and structural (cell wall) components. Correlations between shearing strength and NDF, ADF and lignin were 0·74, 0·82 and 0·80 respectively. The technique identified clear differences between accessions of the same species (P 〈 0·05). These measurements can thus be used as a powerful tool for identifying forage plants of superior nutritional quality within selection programmes. Measurements of strength standardized for morphological characteristics illustrated that the ranking of the samples varied considerably depending on which morphological character was used.

Description: SUMMARYInvestigations into the non-protein nitrogen composition of grass silages using the 50 cm strong cation-exchange column of Spackman, Stein & Moore (1958) to determine the basic amino acids led to difficulties in the determination of ethanolamine in the presence of high concentrations of ammonia, and of histidine in the presence of δ amino-n-valeric acid. An alternative technique for the ion exchange chromatography and estimation of histidine, lysine, ornithine, ethanolamine, arginine and ammonia on a weak cation-exchange resin has been developed. This method enables small amounts of ethanolamine to be determined in the presence of large amounts of ammonia and values for the ethanolamine content of a number of silage samples are presented. When used in conjunction with the technique of Spackman et al. (1958) the δ-amino-n-valeric acid content of grass silages could also be determined in the presence of histidine.The estimation of amines produced by the microbial decomposition of herbage proteins during ensiling has previously involved their initial separation from the amino acids followed by quantitative partition chromatography. An alternative method for the estimation of these amines by ion-exchange chromatography on a weak cation-exchange resin is described. This method permits the colorimetric determination of β-phenylethylamine, tyramine, tryptamine, 5-hydroxytryptamine, putrescine, cadaverine and histamine without interference from the amino acids. The efficiency of this technique has been investigated using standard solutions of the naturally occurring amines and samples of good quality and of high pH spoilt silages.