Equine Veterinary Journal Early View January 2016

Heather Ferguson


Bodyweight change aids prediction of survival in chronic equine grass sickness

R. C. Jago, I. Handel, C. N. Hahn, R. S. Pirie, J. A. Keen, B. E. Waggett and B. C. McGorum



This retrospective observational study aimed to identify an objective predictor of survival in chronic equine grass sickness. The records of 213 cases were reviewed: minimum weight, time from first weight to minimum weight, duration of disease on admission and duration of hospitalisation were compared in both survivor and nonsurvivor groups.


There were 114 (53.5%) survivors and 99 (46.5%) nonsurvivors. The most common indication for euthanasia was recumbency and inability to stand. There was no significant difference in age or duration of disease prior to hospitalisation between survivors and nonsurvivors: 50% of nonsurvivors were euthanased by 21 days and 75% by 32 days from disease onset. Survivors were hospitalised for longer than nonsurvivors, with 50% being discharged by day 42.

Survivors had lower maximum bodyweight loss (as percentage of initial weight) compared to nonsurvivors. Survivors also had a significantly earlier day of minimum weight and lower weight loss than nonsurvivors at all time points. All nonsurvivors lost weight during hospitalisation, whereas some survivors rapidly reached their lowest weight with some even gaining weight during hospitalisation.


The greatest percentage bodyweight loss occurred between 0 and 7 days of hospitalisation in both groups. This figure was similar in individuals from both groups, indicating that cases can survive despite significant weight loss and that this alone is not an indicator for euthanasia. Survival prediction curves were compiled against which a horse’s bodyweight change between any time intervals can be compared to predict survival rate.



Bottom line:


In chronic grass sickness, bodyweight change is a significant predictor of survival.




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