Objective—To determine the pulmonary epithelial lining
fluid (ELF) concentrations and degree of oxidation
of ascorbic acid in horses affected by recurrent airway
obstruction (RAO) in the presence and absence of
neutrophilic airway inflammation.
Animals—6 RAO-affected horses and 8 healthy control
Procedure—Nonenzymatic antioxidant concentrations
were determined in RBC, plasma, and ELF samples
of control horses and RAO-affected horses in the
presence and absence of airway inflammation.
Results—ELF ascorbic acid concentration was
decreased in RAO-affected horses with airway inflammation
(median, 0.06 mmol/L; 25th and 75th percentiles,
0.0 and 0.4 mmol/L), compared with RAOaffected
horses without airway inflammation (1.0
mmol/L; 0.7 and 1.5 mmol/L) and control horses
(2.2 mmol/L; 1.4 and 2.2 mmol/L). Epithelial lining fluid
ascorbic acid remained significantly lower in RAOaffected
horses without airway inflammation than in
control horses. Moreover, the ELF ascorbic acid redox
ratio (ie, ratio of the concentrations of dehydroascorbate
to total ascorbic acid) was higher in RAO-affected horses
with airway inflammation (median, 0.85; 25th and
75th percentiles, 0.25 and 1.00), compared with RAOaffected
horses without airway inflammation (0.04; 0.02
and 0.22). The number of neutrophils in bronchoalveolar
lavage fluid was inversely related to the ELF ascorbic
acid concentration ( r = –0.81) and positively correlated
with the ascorbic acid redox ratio ( r= 0.65).
Conclusions and Clinical Relevance—Neutrophilic
inflammation in horses affected by RAO is associated
with a reduction in the ELF ascorbic acid pool.
Nutritional supplementation with ascorbic acid derivatives
in horses affected by RAO is an area for further
investigation. ( Am J Vet Res2004;65:80–87)
Objective—To develop proxies calculated from basal
plasma glucose and insulin concentrations that predict
insulin sensitivity (SI; L·min–1·mU–1) and beta-cell
responsiveness (ie, acute insulin response to glucose
[AIRg]; mU/L·min–1) and to determine reference quintiles
for these and minimal model variables.
Animals—1 laminitic pony and 46 healthy horses.
Procedure—Basal plasma glucose (mg/dL) and insulin
(mU/L) concentrations were determined from blood
samples obtained between 8:00 AM and 9:00 AM.
Minimal model results for 46 horses were compared
by equivalence testing with proxies for screening SI
and pancreatic beta-cell responsiveness in humans
and with 2 new proxies for screening in horses (ie, reciprocal
of the square root of insulin [RISQI] and modified
insulin-to-glucose ratio [MIRG]).
Results—Best predictors of SI and AIRg were RISQI
(r = 0.77) and MIRG (r = 0.75) as follows: SI =
7.93(RISQI) – 1.03 and AIRg = 70.1(MIRG) – 13.8,
where RISQI equals plasma insulin concentration–0.5
and MIRG equals [800 – 0.30(plasma insulin concentration
– 50)2]/(plasma glucose concentration – 30).
Total predictive powers were 78% and 80% for RISQI
and MIRG, respectively. Reference ranges and quintiles
for a population of healthy horses were calculated
Conclusions and Clinical Relevance—Proxies for
screening SI and pancreatic beta-cell responsiveness
in horses from this study compared favorably with
proxies used effectively for humans. Combined use
of RISQI and MIRG will enable differentiation
between compensated and uncompensated insulin
resistance. The sample size of our study allowed for
determination of sound reference range values and
quintiles for healthy horses. (Am J Vet Res
Objective—To compare effects of oral supplementation
with an experimental potassium-free sodiumabundant
electrolyte mixture (EM-K) with that of oral
supplementation with commercial potassium-rich
mixtures (EM+K) on acid-base status and plasma ion
concentrations in horses during an 80-km endurance
Animals—46 healthy horses.
Procedure—Blood samples were collected before
the ride; at 21-, 37-, 56-, and 80-km inspection points;
and during recovery (ie, 30-minute period after the
ride). Consumed electrolytes were recorded. Blood
was analyzed for pH, PvCO2, and Hct, and plasma was
analyzed for Na+, K+, Cl–, Ca2+, Mg2+, lactate, albumin,
phosphate, and total protein concentrations. Plasma
concentrations of H+ and HCO3–, the strong ion difference
(SID), and osmolarity were calculated.
Results—34 (17 EM-K and 17 EM+K treated) horses
finished the ride. Potassium intake was 33 g less and
Na+ intake was 36 g greater for EM-K-treated horses,
compared with EM+K-treated horses. With increasing
distance, plasma osmolarity; H+, Na+, K+, Mg2+,
phosphate, lactate, total protein, and albumin concentrations;
and PvCO2 and Hct were increased in all
horses. Plasma HCO3–, Ca2+, and Cl– concentrations
were decreased. Plasma H+ concentration was significantly
lower in EM-K-treated horses, compared with
EM+K-treated horses. Plasma K+ concentrations at
the 80-km inspection point and during recovery were
significantly less in EM-K-treated horses, compared
with EM+K-treated horses.
Conclusions and Clinical Relevance—Increases in
plasma H+ and K+ concentrations in this endurance
ride were moderate and unlikely to contribute to signs
of muscle fatigue and hyperexcitability in horses. (Am J Vet Res 2005;66:466–473)
To investigate equine squamous gastric disease (ESGD) and equine glandular gastric disease (EGGD) in Icelandic horses moving from pasture into training.
81 horses (median age, 3 years; interquartile range, 1 year) from 10 farms representing 4 different Icelandic regions.
Initial gastroscopy was undertaken within 2 weeks of moving from pasture into a training establishment. A total of 71 horses underwent endoscopic examination again 8 weeks later. Various management and behavioral factors were assessed through face-to-face questionnaires with the owners or trainers. Multivariable logistic regression was used to determine factors contributing to any change in ESGD and EGGD severity score during the 8-week training period.
Incidence of EGGD and ESGD in this feral population was similar to that found in domesticated horses. ESGD incidence (severity score, ≥ 2; score range, 0 to 4) reduced from an initial 71.6% (58/81) to 25.4% (18/71). On multivariable analysis, sex (ie, being a stallion or a female vs gelding) increased the likelihood of ulcer grade reduction. Being fed preserved forage 3 or more times a day also improved the likelihood of ESGD reduction (odds ratio, 17.95; 95% CI, 1.67 to 193.40; P = .017). Overall, the farm explained 35% of the variance, confirming the importance of management factors. Incidence of EGGD (severity score, ≥ 1; score range, 0 to 2) reduced from 47% (38/81) to 40.8% (29/71) during the same period. No measured variables were associated significantly with EGGD incidence or reduction.
Pasture provision (without supplementary feed or forage) does not result automatically in a low incidence of gastric ulcers. Regular provision of preserved forage is a key factor in reducing ESGD incidence.