Abstract
Fescue toxicosis is a multifaceted syndrome common in cattle grazing endophyte-infected tall fescue; however, varying symptomatic responses potentially imply genetic tolerance to the syndrome. It was hypothesized that a subpopulation of animals within a herd would develop tolerance to ergot alkaloid toxicity. Therefore, the goals of this study were to develop selection criteria to identify tolerant and susceptible animals within a herd based on animal performance, and then examine responsive phenotypic and cytokine profiles to fescue toxicosis. Angus cows grazed endophyte-infected tall fescue at two locations for 13 weeks starting in mid-April 2016. Forage measurements were collected to evaluate ergot alkaloid exposure during the study. A post hoc analysis of animal performance was utilized to designate cattle into either tolerant or susceptible groups, and weekly physiological measurements and blood samples were collected to evaluate responses to chronic exposure to endophyte-infected tall fescue. Findings from this study support the proposed fescue toxicosis selection method formulated herein, could accurately distinguish between tolerant and susceptible animals based on the performance parameters in cattle chronically exposed to ergot alkaloids, and provides evidence to warrant additional analysis to examine the impact of ergot alkaloids on immune responsiveness in cattle experiencing fescue toxicosis.
Highlights
Fescue toxicosis, resulting from consumption of ergot alkaloids commonly found in endophyte (Epichloë coenophiala)-infected tall fescue
The goals of this study were to develop selection criteria to identify tolerant and susceptible animals based on phenotypic animal performance traits, to evaluate how our criteria matches with the information from a commercial test for fescue toxicosis, and examine responsive cytokine profiles to identify beef cattle displaying tolerance to fescue toxicosis
While the concentration of ergovaline decreased during period 2 (P-2), these concentrations were still high enough to elicit many of the negative symptoms associated with fescue toxicosis [7,8]
Summary
Fescue toxicosis, resulting from consumption of ergot alkaloids commonly found in endophyte (Epichloë coenophiala)-infected tall fescue Galliou et al [5] tested the association between genotypes from a commercial genetic test for fescue toxicosis and performance in pregnant Angus cows. These authors found significant associations with growth, hair shedding, and calf weaning weight. These pose a major challenge to understanding the underlying mechanisms of action responsible for the decreases in livestock productivity. While advancements have been made to better understand the mechanisms associated with fescue toxicosis symptoms, such as focusing on improving growth and reproductive performance of beef cattle grazing endophyte-infected tall fescue, a greater understanding is needed to identify markers for tolerance to fescue toxicosis, which is critical for the sustainability of the global beef industry
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