43 Safety of chromium propionate as a source of supplemental chromium for horses

Abstract

Chromium propionate (Cr Prop) was recently approved by the US FDA for supplementation to horse feed at a level not to exceed 4 mg Cr/horse/day. This approval was based on the ability of Cr Prop to improve insulin sensitivity in adult horses following oral consumption of grain or intravenous administration of glucose, and also on the safety of Cr Prop when supplemented to horse diets at up to 2 times the FDA approved level. The objective of the current study was used to determine the safety of Cr Prop based on health, body weight (BW) gain, body condition score, and blood chemistry and hematological parameters when supplemented at levels of 0, 2, 4, or 8 mg Cr/day. Forty-eight registered Quarter horses were used in this study. The study was conducted as 4 trials, due to a limitation of individual stalls at the testing facility. Horses were housed individually and fed twice daily an oat-based concentrate mix at a rate of 0.2 kg/100 kg BW, and grass hay (2 kg/100 kg BW). Supplemental Cr was provided in 50 g of ground corn/day that was top dressed on the morning feeding of concentrate. In the fourth trial, 12 horses (n = 3/treatment) were bled before feeding on d 0 and 28 of the trial for blood chemistry and hematological measurements. Serum was analyzed for an Equine Chemistry panel, that consisted of calcium, phosphorus, magnesium, sodium, potassium, chloride, bicarbonate, osmolality, anion gap, glucose, urea, total protein, albumin, bilirubin, alkaline phosphatase, aspartate aminotransferase, and creatine kinase. A sample of whole blood also was obtained for a variety of hematological measurements. Each horse served as its own control, because d 28 blood data were statistically analyzed using d 0 blood values as a covariate. Feeding Cr Prop for 42 d did not affect health, body weight gain, or body condition score. Control horses had lower ( P ≤ 0.05) RBC counts than those fed 8 mg Cr/day, and tended to have lower RBC counts than those receiving 2 ( P = 0.07) or 4 ( P = 0.06) mg Cr/day. Other hematological measurements were not affected by dietary Cr. Serum clinical chemistry parameters measured were not affected by treatment. The present study indicates that Cr Prop is safe when supplemented to horses at up to 2 times the FDA approved feeding level.