Genetic variation in the nutritive value of Gliricidia sepium.: 2. Leaf chemical composition and fermentability by an in vitro gas production technique

Five Gliricidia sepium provenances, comprising three central American native populations and two land races, were grown at five sites. Replicated leaf samples were evaluated by an in vitro gas production technique, estimation of crude protein (CP), acid detergent fibre (ADF), neutral detergent fibre (NDF) and coumarin content. Differences between provenances in fermentation characteristics generally achieved statistical significance (p<0.05) at all five sites, but were small (13% range or less). Significant differences (p<0.05) were found between samples of young and old leaves, leaves from sunny and shady plots and between air-dried and freeze-dried samples. Differences due to site were highly significant for all fermentation characteristics, and much greater than differences due to provenance. The compositional analyses showed highly significant genetic variation in CP and ADF, but not in NDF or coumarin levels. Again, the range of values was small (<10%), and was dwarfed by site-related effects. The reasons for the site related differences were not identified. The narrow range of provenance means for all the traits measured, compared with the considerable site-related variability, suggested that intraspecific variation in nutritive value of these five provenances of Gliricidia sepium was unlikely to be of great practical importance to livestock keepers.