The effect of omega-3 fatty acid supplementation and a controlled-release intramuscular thyroxine injection on serum insulin concentrations in horses
Abstract: A completely randomized design experiment was conducted to examine the effects of omega-3 fatty acid and thyroxine supplementation on serum thyroxine and insulin concentrations in horses. Thirty-thee geldings and 11 mares (aged 5 to 27 yr) were stratified by preliminary 4-h postprandial serum insulin concentration. All horses were then randomly assigned to 1 of 3 treatments: control (C), daily oral omega-3 PUFA supplementation (O), or monthly controlled-release IM thyroxine microparticle injection (T). The 114-d trial consisted of a d 0 baseline sample, followed by a 30-d and 3 subsequent 28-d periods, named for the month in which the sample was collected – August, September, October, November and December. At the beginning of each period, venous blood was collected to determine serum thyroxine and insulin concentrations. Thyroxine-treated horses had greater (P < 0.001) serum thyroxine concentrations compared to both C and O horses. Thyroxine-treated horses had decreased (P ≤ 0.05) serum insulin concentrations compared to both C and O horses.
Results from this experiment indicate that IM thyroxine microparticle injection is an effective method of increasing serum thyroxine concentrations results in decreased serum insulin concentrations compared to untreated animals.
Shayna N. Chewning, M.S.* and Lance A. Baker, Ph.D.
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