Pathological changes seen in horses in New Zealand grazing Mediterranean tall fescue (Lolium arundinaceum) infected with selected endophytes (Epichloë coenophiala) causing equine fescue oedema.
Abstract: To investigate whether Mediterranean tall fescue (Lolium arundinaceum (Schreb.) Darbysh. (syn Festuca arundinacea)) infected with selected fungal endophytes (Epichloë coenophiala (formerly Neotyphodium coenophialum)) caused equine fescue oedema when grown in New Zealand, and to examine the pathological changes associated with this intoxication. Methods: Horses were grazed on Mediterranean tall fescue that was infected with the endophytes AR542 (n=2), or AR584 (n=3), or Mediterranean tall fescue that was endophyte-free (n=2). Blood samples were taken up to 7 days after the start of feeding to detect changes in concentrations of total protein in serum and packed cell volume. Any horse showing clinical evidence of disease was subject to euthanasia and necropsy. Results: Within 6 days, both horses grazing fescue infected with AR542 became depressed and lethargic. One horse grazing fescue infected with endophyte AR584 became depressed within a 5-day feeding period while another horse in this group died shortly after being removed from the AR584 pasture. The third horse in this group did not develop clinical signs within the 5-day feeding period. However, haemoconcentration and hypoproteinaemia was detected in all horses grazing Mediterranean tall fescue that was infected by AR542 or AR584 endophyte. No abnormalities were observed in horses grazing fescue that was endophyte-free. Necropsy examination was performed on two horses grazing fescue infected with AR542 and one horse grazing fescue infected with AR584. All three horses had marked oedema of the gastrointestinal tract. Histologically, the oedema was accompanied by large numbers of eosinophils, but no necrosis. Conclusions: Horses grazing Mediterranean tall fescue that was infected by AR542 or AR584 developed hypoproteinaemia and haemoconcentration, most likely due to leakage of plasma proteins into the gastrointestinal tract. This suggests that these selected endophytes produce a compound that is toxic to horses, although the toxic principle is currently unknown. Conclusions: Mediterranean tall fescue that is infected by AR542 or AR584 should not be fed to horses in New Zealand. This intoxication should be considered in horses in which a rapid onset of hypoproteinaemia and haemoconcentration is detected. This intoxication should also be considered if marked gastrointestinal oedema is observed.
Publication Date: 2016-11-06 PubMed ID: 27750516DOI: 10.1080/00480169.2016.1248516Google Scholar: Lookup
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- Journal Article
- Randomized Controlled Trial
Summary
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The research investigates the impact of Mediterranean tall fescue infected with specific fungal endophytes on horses. The research establishes that these endophytes lead to hypoproteinaemia, haemoconcentration, gastrointestinal edema in horses, and advises against the usage of this fungus-infected fescue as horse feed in New Zealand.
Investigation Approach
- The study targeted Mediterranean tall fescue, a type of grass common in New Zealand, infected with specific endophytes (fungus) AR542 and AR584, which have been suspected of causing equine fescue oedema (swelling caused by excess fluid in horse’s body tissues).
- A total of five horses were used in this experiment. Two were fed fescue infected with AR542, three were fed fescue infected with AR584, while two horses were fed endophyte-free fescue as a control group.
- Observations were conducted over a 7-day period, with blood samples taken regularly to detect changes in total protein and packed cell volume in the serum.
- Any horse that showed signs of disease was put to sleep and subjected to a necropsy (animal autopsy) to further study the effects of the infected fescue.
Key Findings
- All horses that consumed the endophyte-infected fescue demonstrated hypoproteinaemia (abnormally low levels of protein in the blood) and haemoconcentration (an increase in the concentration of cells and solids in the blood).
- By the end of the feeding period, horses showed signs of depression and lethargy, with one of the horses dying shortly after being removed from the paddock.
- Gastrointestinal oedema was found in the gastrointestinal tract of all tested horses, accompanied by a substantial presence of eosinophils (white blood cells), but there was no necrosis (tissue death).
- All these symptoms suggest that the fungus-produced toxins that could be harmful to horses, even though the researchers couldn’t pinpoint the precise toxic principle.
- Horses fed with endophyte-free fescue didn’t show any abnormal health signs, confirming it was indeed the endophytes causing the health issues.
Concluding Remarks
- In conclusion, the research advocates that in areas like New Zealand, horses should not be allowed to graze on fescue infected by AR542 or AR584.
- The discovered condition should be considered whenever there’s an unexplained and rapid onset of hypoproteinaemia, haemoconcentration, or marked gastrointestinal oedema in horses.
Cite This Article
APA
Munday JS, Finch SC, Vlaming JB, Sutherland BL, Fletcher LR.
(2016).
Pathological changes seen in horses in New Zealand grazing Mediterranean tall fescue (Lolium arundinaceum) infected with selected endophytes (Epichloë coenophiala) causing equine fescue oedema.
N Z Vet J, 65(3), 147-151.
https://doi.org/10.1080/00480169.2016.1248516 Publication
Researcher Affiliations
- a Pathobiology, Institute of Veterinary, Animal and Biomedical Sciences , Massey University , Private Bag 11222, Palmerston North 4442 , New Zealand.
- b Ruakura Research Centre , AgResearch Ltd. , Private Bag 3123, Hamilton , New Zealand.
- a Pathobiology, Institute of Veterinary, Animal and Biomedical Sciences , Massey University , Private Bag 11222, Palmerston North 4442 , New Zealand.
- c Lincoln Research Centre , AgResearch Ltd. , Private Bag 4749, Christchurch , New Zealand.
- c Lincoln Research Centre , AgResearch Ltd. , Private Bag 4749, Christchurch , New Zealand.
- b Ruakura Research Centre , AgResearch Ltd. , Private Bag 3123, Hamilton , New Zealand.
- c Lincoln Research Centre , AgResearch Ltd. , Private Bag 4749, Christchurch , New Zealand.
MeSH Terms
- Animal Feed / microbiology
- Animals
- Food Microbiology
- Horse Diseases / chemically induced
- Horse Diseases / pathology
- Horses
- Lolium / microbiology
- Mycotoxins / toxicity
- Neotyphodium / metabolism
Citations
This article has been cited 1 times.- Cibils-Stewart X, Powell JR, Popay AJ, Lattanzi FA, Hartley SE, Johnson SN. Reciprocal Effects of Silicon Supply and Endophytes on Silicon Accumulation and Epichloë Colonization in Grasses. Front Plant Sci 2020;11:593198.
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