Location: Forage-animal Production Research
Project Number: 5042-32630-004-010-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Aug 1, 2023
End Date: Jul 31, 2025
Objective:
Experiment 1: A grazing experiment to determine the role of adaptation to grazing system and environment on rumen microbial communities, nutrient utilization, reproductive, and growth performance in first calf beef heifers and cows and their calves.
Experiment 2: Grazing experiments to evaluate the use of remote sensing technology in generating a phenotype of ergot alkaloid exposure that can be used to characterize genetic tolerance to these toxins and fescue toxicosis.
Experiment 3: Grazing experiments to determine the impact of red clover leaf containing mineral on reproductive health and performance in beef cows/heifers and heat stress and growth of growing steers grazing endophyte-infected tall fescue pastures.
Approach:
Experiment 1: Each year, two groups of 9-mo heifers will be selected from Central Kentucky (endophyte infected tall fescue [E+ TF] adapted; n = 30) or from the USDA ARS Fort Keogh, Livestock and Range Research Laboratory, Miles City, MT (E+ TF naïve; n = 45). Native MT heifers will be randomly assigned to three treatments (n = 15 heifers/trt): 1) MT control, 2) MT transported to KY, E+ TF, or 3) MT transported to KY E- [endophyte-free] TF; and native KY heifers will be randomly assigned to two treatments: 1) KY control or 2) KY transported to MT. At 10-mo heifers will be transported to their assigned locations to start treatments and bred at 14-mo of age via timed artificial insemination. Ovarian mapping, corpus luteum area, conception, and caudal artery areas will be monitored via ultrasound. Remote sensing ear tags will be used for fertility, activity, nutrition, and health monitoring. A sub-set of heifers and their calves will be selected for serial rumen, fecal, and jugular blood sampling. Rumen and fecal samples will be analyzed for microbial communities. Blood samples will be analyzed for estradiol, progesterone, blood urea nitrogen, cortisol and prolactin. Forage mass, nutritive value, and composition will be monitored. Weather data will be collected at both locations.
Experiment 2: Grazing experiments will be conducted with cows, heifers, or steers (n = 75/year) on E+TF pastures. Cattle will be fitted with remote sensing technology and sampled from early May to late August. Real time data collected will include body temperature, rumination time, total activity, and activity predictions. Additional data will include breed type, body condition, hair coat score, body weight, caudal artery area, and calving history and success (heifers/cows only). Weather data from local weather stations nearest to each site
will also be collected. Percent E+ TF will be assessed and ergovaline concentrations of tillers will be analyzed to assess pasture toxicity potential. Jugular blood samples will be collected from each animal for DNA genotyping/sequencing (USDA-ARS, Meat Animal Research Center and prolactin. Collected phenotype and environmental data will be used in conjunction with the genomic data to assess tolerance or susceptibility to fescue toxicosis to identify genetic markers that confer resistance.
Experiment 3: Grazing experiments will be conducted with 30 beef steers or 30 heifers/cows per year that will graze 12, 3.0 ha sub-divided pastures of toxic endophyte-infected tall fescue (E+ TF). Each grazing group will be assigned to either a conventional loose mineral control or the same conventional mineral amended with 20% w/w red clover. Grazing will be initiated mid-April and end late-October. Reproductive ultrasound scans (heifers/cows only), breeding statistics (heifers/cows only), average daily gain, body condition scores, respiration rates and haircoats will be collected. Jugular blood will be collected every 30-d for blood urea nitrogen and prolactin.
