Effect of trace mineral proteinates on growth and skeletal and hoof development in yearling horses

Fifteen yearlings, nine Thoroughbreds and six Quarter Horses, were used in a feeding trial to determine whether proteinated trace minerals were utiliz ed advantageously over inorganic trace minerals for growth and development when included in the diet at normal supplementation levels. The animals wer e assigned randomly within breed and gender subgroups to one of two treatme nts. Group A received a 12% protein (as fed) concentrate containing a trace mineral premix providing inorganic trace minerals at concentrations approp riate to supplement Coastal Bermuda grass (Cynodon dactylon) hay and provid e NRC1 or higher trace mineral intakes. Group B was provided the same conce ntrations of trace minerals but the Cu, Mn, and Zn were provided via a comm ercial proteinate. The concentrates were fed to appetite individually, twic e daily during a 1.5-hour feeding period. The hay was group-fed in drylot p addocks at 1.0 kg/100 kg BW daily. The animals were housed three or four an imals per paddock. Weight and body and hoof growth measurements were taken at the start of the experiment and at 28-day intervals for 112 days. Radiog raphs of the third metacarpal were made for estimating bone mineral and hoo f samples were collected at the start and completion of the experiment. The yearlings gained 0.77 +/-0.03 and 0.79 +/-0.03 kg/d for the inorganic and proteinate groups, respectively. None of the body measurements were affecte d by diet (P > 0.10) except hip height gain which was higher for the animal s receiving the proteinated minerals (7.0 vs 4.7 cm, P = 0.023). Hoof growt h was greater for yearlings fed the mineral proteinate than for those fed t he inorganic minerals (4.98 vs 4.78 cm, P = 0.016), and colts had greater h oof growth than did fillies (5.00 vs 4.72 cm, P = 0.003). Diet and gender d id not affect hoof strength (P > 0.10), but Quarter Horses had greater hoof strength than Thoroughbreds (98.2 vs 88.8 kg, P = 0.046). No differences i n bone mineral content or bone mineral deposition were detected (P > 0.10).