The Influence on Growth of of Mineral Supplementation and Skeletal Development Yearling Horses 1

Forty-six Thoroughbred and Quarter Horse yearlings were used in two experiments to evaluate the effect of mineral supplementation on growth and skeletal development. In the first experiment, concentrate and bermudagrass hay diets providing 2.82 Mcal DE/kg (estimated), 13.0% CP, .62% Ca and .43% P on a DM basis were supplemented with trace minerals (TM) by adding 0, .5 or 1.0% TM premix to the concentrate. The TM content of the three diets (concentrate and hay) in mg/kg DM were: Fe 150, 162 and 176; Mn 56, 60 and 64; Zn 36, 53 and 69; and Cu 7, 8 and 11 for the low, medium and high TM levels, respectively. No effects of TM intake on feed intake, weight gain or body measurements were detected, but bone mineral deposition was increased by the high TM intake (P < .02). No gross skeletal abnormalities were detected. In the second experiment, a basal diet with Ca and P concentrations near NRC (1978) recommendations was supplemented with no TM, TM or TM + Ca + P. The basal diet had TM concentrations similar to the highest TM levels in the first experiment. The two groups fed added minerals consumed more concentrate and total feed (P < .1) than those receiving the basal diet. Weight gain was increased by the TM supplementation (P < . 1). There was no other diet effect on growth or development of the animals. Colts gained more height than fillies did (P < .05). Results of these two experiments suggest that TM supplementation may have a positive effect on bone mineral deposition in yearling horses, but only when the TM content of the natural diet is below NRC (1978) recommendations. (