I wanted to share this information, because I know what a frustrating and debilitating problem COPD can be for many horses and their owners.
The following comes from the American Association of Equine Practitioners (AAEP) PROCEEDINGS (1997, Vol. 43) which is a book documenting all the studies that are presented at the AAEP annual convention. I am unable to post the entire study here, due to copyright restrictions, but I have tried to pull the relevant quotes.
Excerpts from “Use of a Calcium Ascorbate Supplement in Therapy of Obstructive Pulmonary Disease” by N. Lee Newman, DVM:
COPD is a commonly diagnosed, generally progressive disease in which traditional drug therapy response is highly variable and medication changes may be frequent. Ascorbic acid has been suggested to be useful in different conditions but has not been evaluated in COPD. A patented calcium ascorbate product [Ester-C, Inter-Cal Corp., 533 Madison Ave., Prescott, AZ
85301] has been described to have superior absorption in some species. Six horses with moderate to severe chronic obstructive pulmonary disease treated with a calcium ascorbate supplement in place of other therapy responded with good to excellent response within 45 days of starting treatment. Although the sample size is small, the consistent response is encouraging. Although further study, including blinded trials, is needed, the availability of an oral, easily administered, and safe supplement to help alleviate the crippling symptoms of COPD can be useful to the practitioner in the control of this disease.
…was administered to each horse at a dose level that provided the ascorbic acid equivalent of 19.8–29.7 g daily; the dose as given either once daily or divided twice daily.
FYI, I found two Ester-C supplements for horses. One made by NatureVet and one by Performance Nutrients available from KVsupply.com.