Objective—To investigate influence of the
Rendement Napole (RN–) mutation on proglycogen
(PG) and macroglycogen (MG) content in skeletal
muscles before and after exercise and evaluate glycogen
concentrations within various muscle fiber types.
Animals—5 pigs with the RN– mutation and 3 noncarrier
Procedure—Pigs performed 2 exercise tests on a
treadmill. In the first, pigs (mean body weight, 27 kg)
ran a distance of approximately 800 m. In the second,
pigs (mean body weight, 63 kg) ran until fatigued.
Biopsy specimens (biceps femoris muscle) for determination
of PG and MG contents were obtained
before and after exercise, 24 hours after the first test,
and 3 hours after the second test. Histochemical
analysis was performed on specimens obtained
before and after the second test.
Results—Before exercise, PG stores did not differ
markedly between groups, but MG stores were
twice as high in pigs with the RN– mutation, compared
with noncarrier pigs. The MG content
decreased to a similar extent in both groups after
exercise. Resynthesis of MG was greater in pigs with
the RN– mutation than in noncarrier pigs by 3 hours
after exercise. A low glycogen content after exercise
was observed in many type I and type IIA fibers and
in some type IIB fibers.
Conclusions and Clinical Relevance—The RN– mutation
was associated with high MG stores in skeletal
muscle that did not influence exercise performance.
The RN– mutation did not impair glycogenolysis during
exercise but may induce faster resynthesis of MG
after exercise. (Am J Vet Res 2005;66:1197–1201)
Objective—To determine the ex vivo leukotriene (LT)
biosynthesis in peripheral blood neutrophils (PBNs)
and inflammatory cells in bronchoalveolar lavage fluid
(BALF) obtained from horses affected with recurrent
airway obstruction (RAO).
Animals—6 RAO-affected and 6 control horses.
Procedure—Before and 6, 24, and 48 hours after
stabling, disease severity was determined subjectively
by clinical and mucus scores and measurement of
the maximal change in pleural pressure (ΔPplmax);
PBNs were isolated and BALF samples were examined
cytologically. The PBN and BALF cells were activated
with a calcium ionophore in the presence of
arachidonic acid, and production of LTC4 and LTB4
was measured per 106 cells.
Results—Clinical and mucus scores and ΔPplmax
increased during stabling in RAO-affected horses, but
not in control horses. In neutrophils and BALF cells
from both groups, production of LTB4 exceeded that
of LTC4. At all times, LTB4 production by PBNs was
less in RAO-affected horses than it was in control
horses. Before stabling, LTB4 production by cells in
BALF was low in RAO-affected horses, but increased
considerably after 6 hours of stabling. This increase
coincided with the migration of neutrophils into the
airways. In control horses, production of LTB4 did not
change during stabling.
Conclusions and Clinical Relevance—Results suggested
increased production of LTB4 in airways of
RAO-affected horses, compared with control horses,
that may contribute to the infiltration of neutrophils
into the lungs and the sustained inflammation associated
with RAO. ( Am J Vet Res 2004;65:289–295)
OBJECTIVE To quantify insulin sensitivity and monitor glucose, insulin, and lipid concentrations in a group of moderately insulin-resistant horses during induction of obesity by use of a forage diet supplemented with fat and during subsequent turnout to pasture.
ANIMALS 9 adult Standardbred mares (11 to 20 years old).
PROCEDURES Weight gain of horses was induced during 22 weeks by use of a forage diet supplemented with fat fed in gradually increasing amounts, followed by feeding of that fat-supplemented diet at 2.5 times the daily maintenance requirements. Horses were then turned out to pasture. Insulin sensitivity was measured with the euglycemic hyperinsulinemic clamp method before and after weight gain and after 4 weeks at pasture. Body weight, body condition score, and cresty neck score as well as fasting and postprandial concentrations of plasma insulin, plasma glucose, serum triglyceride, and serum nonesterified fatty acids were measured during the study.
RESULTS Body weight typically increased by 10%, and body condition score (scale, 1 to 9) increased by > 1.5 from the start to the end of the weight-gain period. There was no difference in insulin sensitivity or metabolic clearance rate of insulin during the weight-gain period. Four weeks at pasture generally improved insulin sensitivity and metabolic clearance rate of insulin by 54% and 32%, respectively, but there was no change in body weight or body condition score.
CONCLUSIONS AND CLINICAL RELEVANCE Findings indicated that dietary composition played a more important role than did short-term weight gain on alterations in insulin sensitivity of horses.