Feed deprivation of mares: plasma metabolite and hormonal concentrations and responses to exercise.

Abstract

Twelve light horse mares were fed a control diet that provided 100% of their maintenance protein and energy requirements for 7 d and were then either continued on the control diet or totally deprived of feed (with access to water) for 3 d . Plasma samples were drawn twice daily throughout the experiment, at 15-min intervals for 9 h beginning 45 h after feed removal, and at 10-min intervals around an exercise bout beginning 73 h after feed removal. Feed deprivation increased (P < or = .06) whole blood beta-hydroxybutyrate and plasma NEFA, urea N, L-lactate, and glucagon concentrations, decreased (P = .02) IGF-I concentrations, and did not change (P > .1) plasma glucose insulin, prolactin, triiodothyronine, and thyroxine concentrations. Exercise increased (P < .05) plasma NEFA, prolactin, and growth hormone (GH) concentrations in all mares. Plasma NEFA concentrations increased (P < .001) after exercise and remained increased in fed mares, but rapidly decreased in deprived mares (time x diet interaction, P = .006). Plasma glucose concentrations following exercise increased in deprived mares but decreased in fed mares (time x diet interaction, P = .07). The plasma prolactin response after exercise also differed between groups (P = .09). Feed-deprived mares had greater (P = .02) plasma GH concentrations before exercise (73 h after feed withdrawal) and had a greater (P < .001) GH peak at 10 min after initiation of exercise. The increase in secretion rate o GH due to feed deprivation in these mares was similar to that reported for other domestic species but was not nearly as great in magnitude.

Comparison of grass haylage digestibility and metabolic plasma profile in Icelandic and Standardbred horses

“…It has earlier been shown that the plasma NEFA concentration increases in horses in negative energy balance (Sticker et al, 1995). However, in the present study the plasma NEFA concentration was not elevated in the Standardbred horses in relation to the Icelandic horses but the Standardbred horses consistently had higher plasma urea concentrations (even on haylage 2, low crude protein feed in relation to the Icelandic horses on haylage 1, high crude protein feed), perhaps indicating catabolic metabolism.…”

Effects of feeding state on glycaemic and insulinaemic responses to a starchy meal in horses: a methodological approach

“…The data from literature provide evidence that the feeding state before feeding of the test diet might influence the glycaemic and insulinaemic responses. Sticker et al (1995) found no significant impact on glucose and insulin responses in protein-or energy-restricted mares, but their non-esterified fatty acids (NEFA) concentrations were 2.5 times higher than those of mares fed control energy. Similar changes were reported by Rose and Sampson (1982) after 24, 48, 72 and 96 h of withholding feed in horses.…”

Prolactin in the Horse: Historical Perspective, Actions and Reactions, and Its Role in Reproduction

“…Thompson et al [21] reported that the prolactin response to exercise was similar in mares, stallions, and geldings when tested in June. Sticker et al [64] compared the prolactin responses to exercise between normal-fed mares and those feed deprived for 73 hours. Although feed deprivation stimulated the exercise-induced growth hormone response, it had no effect on the immediate release of prolactin.…”