Ca. Williams et al., Plasma glucose and insulin responses of Thoroughbred mares fed a meal highin starch and sugar or fat and fiber, J ANIM SCI, 79(8), 2001, pp. 2196-2201
Plasma concentrations of glucose and insulin following a meal were compared
in twelve Thoroughbred mares fed a pelleted concentrate (PC), a traditiona
l sweet feed high in sugar and starch (SS), or a feed high in fat and fiber
(FF). The feeds had similar DE and CP but differed in fat (19, 32, and 166
g/kg DM, respectively), NDF (199, 185, and 369 g/kg DM, respectively) and
nonstructural carbohydrates (574, 645, and 247 g/kg, respectively). Mares w
ere randomly assigned to two groups balanced for foaling date and weight. A
ll mares received PC in late gestation; then, after foaling, one group was
fed SS and the other FF for trials in early and late lactation. Mares were
placed in stalls and deprived of feed overnight. A series of blood samples
was collected via a jugular catheter from 0 (baseline) to 390 min after con
sumption of 1.82 kg of feed. Plasma was analyzed for glucose and insulin. B
aseline values, peak values, and areas under curves (AUC) were compared by
ANOVA. Baseline values were 74.7 +/- 10.9 mg/dL for glucose and 5.86 +/- 1.
80 mIU/L for insulin for all diets and stages. Responses to PC did not diff
er between the two groups (P > 0.34), indicating the groups were metabolica
lly similar. Peak plasma glucose and insulin concentrations were higher (P
< 0.001) in the SS group than in the FF group during early and late lactati
on. Similarly, glucose and insulin AUC were larger (P < 0.003) in SS than i
n FF during early and late lactation. These results indicate that metabolic
fluctuations are moderated by the replacement of sugar and starch with fat
and fiber. This replacement may reduce the risk of certain digestive and m
etabolic disorders that have been linked to feeding meals of grain-based co
ncentrates to pregnant or lactating mares.