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Summary The trace element chromium (Cr) has attracted attention because Cr supplements have been shown to benefit biological functionality and health in both humans and animals. It has been suggested that Cr decreases insulin levels and improves glucose disposal in type 2 diabetic and obese humans. Therefore, the aim of the study was to examine the effect of feeding Cr-enriched yeast on glucose metabolism in insulin-resistant ponies and horses. 27 insulin-resistant ponies and horses, mean age (±SD) 13.9 (±4.8) years, mean body mass (±SD) 422 (±138) kg, mean body condition score (±SD) 7.6 (±0.8) on a scale of 1–9, were used in a placebo-controlled study. The ponies and horses were fed for four weeks either a yeast product without Cr (= placebo, N = 12), or a Cr-enriched yeast (= verum, 2 g organic Cr3+/kg yeast, 25 µg/kg BW, N = 15). During experimental period all animals were on a hay-based diet (1.2 kg hay/100 kg BW). A starch tolerance test (STT, 1.5 g starch/kg BW) was performed at the beginning and at the end of the study. Blood was collected following a standardized protocol. Plasma glucose concentrations were determined by glucose oxidase assay and plasma insulin was determined by radioimmunoassay. The STT revealed exaggerated glucose and insulin responses, reflecting an impaired glucose tolerance in all animals. Postprandial insulin responses were significant higher at the beginning of the study in the group to be fed verum when compared to the placebo group. After supplementation, plasma insulin responses were significantly modified by Cr intake (diet p < 0.05), suggesting an improved glucose regulation. Plasma glucose responses were not affected by the different treatments. Cr supplementation for four weeks improved glucose metabolism in ponies and horses suggesting that Cr facilitated insulin signaling. However, it must be emphasized that the ponies and horses still had impaired glucose regulation as indicated by supraphysiological glucose and insulin responses to the STT when compared to healthy horses. |
