Use of the in situ technique in the study of degradation of lucerne and smooth bromegrass genotypes

Abstract

AbstractSix lucerne (Medicago sativa) genotypes (Beaver, Vernal and four other strains being developed at the University of Alberta) and five smooth bromegrass (Bromus inermis) genotypes (Carlton, Magna and three genotypes being developed) were examined in terms of forage dry matter (DM) yield and degradability, as determined by the rate and amount of material which disappeared from bags suspended in the rumen of cattle. Dry matter yield did not differ (p > 0·05) between lucerne genotypes at first cut. The smooth bromegrass strain 517 had a proportionately Oil higher (P < 0·05) DM yield than did the Magna strain. No differences (P < 0·05) were detected within either smooth bromegrass or lucerne genotypes for 48 or 60 h in situ DM degradability. The 416E smooth bromegrass genotype, however, had a significantly higher (P < 0·05) rate of DM degradation in the rumen than the other genotypes and also exhibited a longer (P < 0·05) lag period before a significant amount of DM degradability occurred. In the in situ technique, approximately eighteen bags would have been needed to obtain DM degradability measurements with a confidence interval of 0·04 for DM degradability of a probability of 0·95. Further in vivo studies with the bromegrass genotypes are warranted to ascertain if the differences in digestion rates and lag times are related to meaningful differences in animal intake and digestibility.