Date of Award

2017

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

First Advisor

Rebecca Nelson-Brown

Abstract

Tanniferous forages, such as birdsfoot trefoil (Lotus corniculatus L.), are a potential control for the parasitic nematode Haemonchus contortus (barber pole worm). Gastrointestinal parasites cause huge economic loss in small ruminant production. Tanniferous forages have been shown to reduce counts of parasite eggs in feces of small ruminants. Currently the tanniferous forage Lespedza cuneate L. is used in the southern United States in control of gastrointestinal nematodes of small ruminants. It is not a viable option in the Northeast due to insufficient winter hardiness. Birdsfoot trefoil is adapted to the Northeast and may be a viable option as a tanniferous forage for small ruminant production if populations exist that combine anthelmintic efficacy with strong agronomic performance. To address this need, I collected data on the agricultural performance of 51 Plant Introductory (PI) accessions and six commercial cultivars.

In a three-year field study (2013, 2014, and 2015) I evaluated growth habit, winter hardiness, pest resistance, uniformity and vigor for 57 populations. In 2015, I tested 19 PI accessions and six commercial cultivars for grazing tolerance, regrowth, and uniformity and vigor in a rotationally grazed pasture trial. Birdsfoot trefoil accessions were chosen for the studies based on condensed tannin contents reported in the literature. Tannin content and in vitro anthelmintic efficacy were compared to agronomic characteristics.

Growth habit was assessed using height/width ratios measured once each year. Winter hardiness was assessed as survival rate counted each spring. Birdsfoot trefoil is susceptible to potato leafhopper; damage by pests were visually evaluated. Quality was visually evaluated based on vigor and uniformity within each population. Vigor and uniformity was assessed yearly in the nursery plantings and immediately before each grazing event in the grazing trial. The eight-week grazing trial allowed for two grazing events for each of the nine replications. Grazing tolerance and regrowth were measured weekly for each replication throughout the eight weeks of grazing.

Accessions and cultivars showed a significant difference in 2013 and 2015 for potato leaf hopper damage (P <0.0001). There were also significant differences between accessions and cultivars for population uniformity and vigor scores and winter survival (P <0.0001). Winter survival ranged from 0 to 100% while uniformity scores of surviving plots ranged from 1 to 5. A positive correlation was seen between plant survival and uniformity and vigor scores both in 2014 and 2015. PI306182, S3149, PI262530, PI262529, and PI255305 were high in vigor and uniformity scores averaged across 2014 and 2015; 2013 scores were not significantly different. ‘Pardee’, ‘Leo’, ‘Empire’ and ‘Bull’ were highest in uniformity and vigor scores for commercial cultivars averaged across 2014 and 2015. Growth habit was measured as height/width ratio and significant differences were seen in 2013 and 2015 but not in 2014. Cluster analysis divided the 51 accessions and six commercial cultivars into 6 clusters. Clusters did not correlate with tannin levels or efficacy but cluster means allowed for evaluation of agronomic characteristics of similar populations. All six commercial cultivars were clustered together in cluster 1 (N= 18) with favorable agronomic characteristic results. All the commercial cultivars also showed high anthelmintic efficacy, with the exception of ‘Bruce’. PI193725, PI162425, PI180171, PI228286 and PI325379 are promising accessions that were included in cluster 1, ranking high across agronomic characteristics and in in vitro anthelmintic efficacy.

In the rotational grazing trial regrowth and combined uniformity and vigor differed significantly between populations for both grazing events. Plant survival varied widely with a low of 56.92% for PI232098 and a high of 95.06% for ‘Empire’. After agronomic characteristics were assessed, anthelmintic efficacy and condensed tannin content were compared. In vitro efficacy and condensed tannin content showed no correlation. High efficacy was positively correlated with plant survival rates and uniformity and vigor. Regrowth was independent of anthelmintic efficacy.

This research identifies commercial cultivars and PI accessions with potential for anthelmintic efficacy against H. contortus and successful agronomic performance as a legume forage in the northeastern U.S. PI193725, PI180171, PI162425, PI228286, PI325379, ‘Empire’,’Norcen’,’Bull’, ‘Pardee’ and ‘Leo’ performed well agronomically and were efficacious in in vitro tests against H. contortus.

Share

COinS