Skip to main content
ARS Home » Research » Publications at this Location » Publication #67077

Title: EVALUATION OF STEM STRENGTH OF ALFALFA (MEDICAGO SATIVA L.) GENOTYPES

Author
item AMES, N - PRC-AGRIC. CANADA
item MCELROY, A - PRC-AGRIC. CANADA
item Akin, Danny
item Lyon, Clyde

Submitted to: Animal Feed Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Physical properties of plant biomass influence feed breakdown of plant stems and thereby limit efficient utilization of feeds by cattle and sheep and increase feeding costs. Tests for objective analysis of these physical properties, and for measuring methods that could remove limitations and improve the value of animal feeds, are lacking. In a collaborative project, ,scientists of ARS and Agricultural Canada tested textural strength, which stimulates the result of animal chewing and particle breakdown, using an Instron universal measuring device. Results were compared for several alfalfa genotypes at several positions of the stem and after fermentation with various rumen microorganisms. Recommendations were developed for optimal measuring conditions of alfalfa stems, and factors most influential on textural strength were identified. Research is important for establishing objective tests for physical properties of plant stems which could be used by plant breeders and animal nutritionists for improving the quality of animal feed.

Technical Abstract: Stem strength, as an estimate of forage intake potential, could be a useful selection parameter in alfalfa (Medicago sativa L.) breeding programs, but there is little information on sampling techniques or the effect of tissue weakening by bacterial or fungal incubation. This study investigated the effect of stem position (top, middle, bottom) and incubation with a water control, Ruminococcus flavefaciens or Neocallimastix MC-2 on stem shear strength of four alfalfa genotypes. Stem diameter was closely associated with shear force in all treatments and was used as a covariate in statistical analyses. Shear strength increased from the top to the bottom of all genotypes regardless of incubation. Both bacterial and fungal incubation reduced (P<0.01) shear strength, with the fungus reducing shear strength to the greatest extent. Genotype differences (P<0.05) across incubation treatments were detected in the bottom stem portions only. There were no genotype x incubation treatment interactions within any stem position, but genotype x position effects (P<0.01) were detected in the water incubation control. The bottom sections of alfalfa showed the largest differences and would provide the best sample material to estimate forage intake potential. Stem diameter should be used as a covariate.