Beef cattle that respond differently to fescue toxicosis have distinct gastrointestinal tract microbiota

Abstract

Tall fescue (Lolium arundinaceum) is a widely used forage grass which shares a symbiosis with the endophytic fungus Epichloë coenophiala. The endophyte produces an alkaloid toxin that provides herbivory, heat and drought resistance to the grass, but can cause fescue toxicosis in grazing livestock. Fescue toxicosis can lead to reduced weight gain and milk yields resulting in significant losses to the livestock industry. In this trial, 149 Angus cows across two farms were continuously exposed to toxic, endophyte-infected, fescue for a total of 13 weeks. Of those 149 cows, 40 were classified into either high (HT) or low (LT) tolerance groups according to their growth performance (weight gain). 20 HT and 20 LT cattle balanced by farm were selected for 16S rRNA gene and ITS1 region Illumina MiSeq amplicon sequencing to compare the fecal microbiota of the two tolerance groups. This study reveals significantly (P<0.05) different bacterial and fungal microbiota between HT and LT cattle, and indicates that fungal phylotypes may be important for an animal’s response to fescue toxicosis: We found that fungal phylotypes affiliating to the Neocallimastigaceae, which are known to be important fiber-degrading fungi, were consistently more abundant in the HT cattle. Whereas fungal phylotypes related to the genus Thelebolus were more abundant in the LT cattle. This study also found more pronounced shifts in the microbiota in animals receiving higher amounts of the toxin. We identified fungal phylotypes which were consistently more abundant either in HT or LT cattle and may thus be associated with the respective animal’s response to fescue toxicosis. Our results thus suggest that some fungal phylotypes might be involved in mitigating fescue toxicosis. The results of our study provide a basis for investigating the functional role of the gastrointestinal microbiota in fescue toxicosis in more detail in the future.

Dominant Remodeling of Cattle Rumen Microbiome bySchedonorus arundinaceus(Tall Fescue) KY-31 Carrying a Fungal Endophyte

“…7). The fecal microbiome of cattle grazing tall fescue also contains Proteobacteria, Euryarchaeota, and Lentisphaera phyla at abundances similar to those observed by us for the rumen (17,18,47).…”

“…We compared our findings with the published information on the fecal microbiome of cattle that grazed tall fescue. In two studies where cattle were moved from a mixed ration to MaxQ and KY-31 in parallel (17,18) (17,18,47). Similar changes were observed in our MaxQ-1 to KY-31 shift (Fig.…”

“…The previous studies on the rumen microbiome of cattle consuming Tall Fescue have primarily focused on the possibilities and mechanisms of microbial degradation of ergovaline as produced by the fungal endophyte of the KY-31 cultivar (11, 17-19, 46, 47). In some of these cases the fecal microbiome was employed as a proxy (17,18,47). The current study had the goals to to MaxQ or KY-31 (17).…”

“…8). On the other hand, the Treponema species which were present at high levels during the MaxQ-1 grazing and had a reduced presence at the KY-31 phase, gained significant abundance in the sessile fraction with the MaxQ-2 ( There have been efforts to use the fecal microbiome as a proxy for monitoring the activities in the rumen under particular diets (49,71) and ruminal conditions (50), and to identify particular fecal microbes as biomarkers for fescue toxicosis (17,18,47). We compared our findings with the published information on the fecal microbiome of cattle that grazed tall fescue.…”

Evaluation of a commercial genetic test for fescue toxicosis in pregnant Angus beef cattle1

“…Results for w1_7 were presented in the main text due to preliminary analysis using these data ( Koester et al, 2020 ) showed that the estimated additive genetic (2.22 [kg/wk] 2 ) and residual (1.09 [kg/wk] 2 ) variances during this period were greater than for the other periods, with 1.04 (kg/wk) 2 and 1.94 (kg/wk) 2 , respectively, for w7_13, and 0.58 (kg/wk) 2 and 1.09 (kg/wk) 2 , respectively, for 1_13, while having similar heritability estimate for these three time windows (~0.35). This is in accordance to reports showing that, under stress/disease conditions, traits show greater additive genetic and residual variances compared with the same traits under a “clean” environment ( Scanlan et al, 2019 ).…”