Project Number: 6227-32630-001-00
Project Type: Appropriated

Start Date: Oct 01, 2007
End Date: Sep 30, 2012

Objective:
The long-term objective of this project is to develop an improved understanding of livestock physiology and genetics to enhance the productivity and profitability of meat production from cattle grazing improved temperate pastures while reducing animal stress. Over the next 5 years this project will focus on the following objectives: Objective 1: Improve grazing animal performance by identifying genes that reduce stress from endophyte-infected cool-season pastures. Subobjective 1.A. Determine if the tropically adapted Romosinuano breed of cattle is more tolerant of heat stress and fescue toxicosis than Angus cattle. Subobjective 1.B. Identify genetic markers in cattle tolerant of heat stress and/or fescue toxicosis. Subobjective 1.C. Determine the role of thermoregulation in tolerance to fescue toxicosis in ruminants. Objective 2: Enhance nutrient utilization from endophyte-infected cool-season forages through improved understanding and manipulation of the microorganisms of the rumen. Objective 3: Develop improved cow-calf and stocker management practices for pastures in which endophyte-infected forages dominate. Subobjective 3.A. Define the effects of ergot alkaloids and lower body condition on cow and/or heifer reproductive performance. Subobjective 3.B. Define sequences of forages and forage management protocols to enhance the productivity and profitability of cow-calf and stocker cattle grazing temperate pastures. Subobjective 3.C. Investigate the mechanisms involved in fecal shedding of pathogenic bacteria from ruminants consuming toxic endophyte-infected (wild type) tall fescue (EI-TF).

Approach:
Physiological parameters (respiration rate, skin and rectal temperature, and blood metabolites) of cattle consuming endophyte-free and -infected fescue diets will be compared in environmentally-controlled chambers. Genetic markers of cattle tolerant to heat stress and/or fescue toxicosis will be assessed. Microarray hybridization will be utilized to obtain estimates of gene expression changes due to heat stress and/or fescue toxicosis within breeds of cattle. Replicated field experiments will evaluate cow-calf and stocker management practices and genotypes on novel, endophyte-free or -infected tall fescue pastures to alleviate fescue toxicosis and improve calf production. Ruminal microbes that are capable of degrading ergot alkaloids will be evaluated. In vivo and in vitro studies will be conducted to determine production practices affecting fecal shedding of E. coli and Salmonella.