Location: Forage-animal Production Research
Project Number: 5042-21500-001-005-I
Project Type: Interagency Reimbursable Agreement
Start Date: Sep 15, 2025
End Date: Sep 14, 2028
Objective:
The aims of the proposed research are to determine effective doses of alfalfa secondary metabolites to prevent fescue toxicosis. This research will also characterize secondary metabolite concentrations in alfalfa varieties adapted to the southeastern United States using two locations with differing climatic conditions. The project will evaluate the influences of factors such as variety, stage of maturity, plant part, yield, nutritive value, and seasonal/environmental impacts on the concentration of these phytochemicals. Finally, this research will evaluate the potential application of alfalfa as a functional feed for preventing fescue toxicosis and ameliorating heat stress in beef cattle. This project will also include the development of an Extension program to educate stakeholders about potential benefits of alfalfa secondary metabolites and use of alfalfa as a functional feed for mitigating fescue toxicosis and heat stress in cattle.
Approach:
Obj. 1. To identify concentrations of alfalfa secondary metabolites that effectively prevent fescue toxicosis, rumen-fistulated beef-cross steers will be subjected to a fescue toxicosis challenge including heat stress. Five levels of each selected secondary metabolite will be tested using a randomized complete block design from 0 to 100 µg g-1 total feed DM. Treatment doses represent normal levels (low to moderate) of secondary metabolites commonly detected in field-grown alfalfa herbage. During the fescue toxicosis challenge, steers will be challenged with ergot alkaloids via endophyte-infected tall fescue (E+ TF) seed and heat stress via an electric heat blanket. E+ TF seed and purified phytochemicals will be dosed through the rumen cannula for 10 d with daily collection of rectal, skin and core body temperature, caudal artery hemodynamics, heart rate, sweating rate, and respiration rates. Blood samples will be collected pre- and post-challenge for quantification of fescue toxicosis and heat stress markers.
Obj. 2A. To characterize secondary metabolite concentrations in alfalfa varieties adapted to the southeastern United States, plot studies will be conducted over a 2-yr period at existing alfalfa variety trial sites in Kentucky and Alabama. Alfalfa varieties selected to represent a range of genetic backgrounds will be evaluated. Biomass will be sampled from plots at early flowering or a minimum of every 4 weeks in the Spring and Fall growing seasons. Alfalfa biomass samples will be clipped for later nutritive value and plant secondary metabolite concentration analyses.
Obj. 2B. To determine the influence of factors such as stage of maturity and plant part on the concentration of these phytochemicals, biomass will be sampled from each plot at the following growth stages: vegetative, early bloom, and late bloom. Plant parts will be manually separated into leaves, stems, and flowers, with subsequent analyses for nutritive value and secondary metabolite concentrations. Obj. 3. Based on results from Obj. 1 and 2, alfalfa varieties containing optimum concentrations of vasoactive secondary metabolites will be selected and harvested. The harvested alfalfa biomass will be used in an animal feeding study in which rumen-fistulated beef-cross steers will be subjected a fescue toxicosis challenge (3A) and a heat stress challenge (3B) as described above for Objective 1. Physiological markers of fescue toxicosis and heat stress will also be measured and analyzed as for Objective 1. Additionally feeding behavior will be continuously monitored using halter-based chew-sensors.
Obj. 4. The Education and Outreach portion of this project is a cooperative partnership between Extension educators in Kentucky and Alabama. These organizations will provide a comprehensive education and outreach effort to reach both forage and livestock producers that will be available to a diverse group of stakeholders: (i) farmers and crop advisors, (ii) extension educators and state agency personnel, (iii) the scientific community (iv) the general public.