77  Trace elements in whole blood and mane hair of horses fed varying sources and levels of trace elements

There has been interest in using hair as a marker for mineral status in horses, but there is a lack of quality research to develop a method to do so. The objectives of this study were to determine if dietary supply of minerals would affect blood and mane hair element concentrations and if there would be a relationship between blood and mane hair element concentrations. Nine mature geldings were used in a replicated 3 × 3 Latin square design. All horses had ad libitum access to forage and 3 dietary treatments were provided by a soybean meal pellet: organic trace minerals (ORG), inorganic trace minerals (ING), and no added trace minerals (CON). The ING and ORG pellet provided the same amount of Co, Cu, Mn, Se, and Zn (between 100 and 380% of NRC requirements), but varied in source and CON provided levels of minerals between 15 and 170% of NRC requirements depending on the mineral. There were 3 21-d treatment periods, including a 5-d washout, so each horse received each treatment. Before the first period, a 3 to 4 cm section of mane hair at the poll was clipped close to the skin. On the last day of each treatment period, blood and mane hair were collected. Mane hair was clipped from the same poll area so only new hair growth was collected. Hair and blood were analyzed for Co, Cr, Cu, Mn, Se, Pb, and Zn using ICP-MS. Data were analyzed using ANOVA with treatment, period, and square replicate as effects. The effect of mane hair color on mineral concentration was evaluated using an ANOVA with hair color as the main effect (black, n = 5; chestnut, n = 3; 1 gray, not included). Means were separated using LSD test. Correlations between hair and blood elements were made using Pearson correlation coefficients. Blood Co tended to be lowest in CON compared with other treatments (P = 0.071). Blood Cr tended to be greatest (P = 0.107) and blood Se was greatest (P < 0.05) in ORG compared with CON, with ING not different from either group. Hair Co was greatest in ORG compared with ING, but CON was not different from either (P < 0.05). Hair Cr tended to be greatest in CON compared with ING, with ORG not different from either (P = 0.102). Hair Pb was greatest in CON compared with the other treatments (P < 0.05). The only correlation between blood and hair was a weak trend for blood Co to be correlated with hair Co (r = 0.347; P = 0.076). Across all treatments, black hair had greater concentrations of Se and lower concentrations of Zn than chestnut hair (P < 0.05). While this study did not find correlations between hair and blood, mineral level and source did alter blood and hair concentrations of certain elements independently, and hair color influences mineral deposition.