Effects of Live Yeast (Saccharomyces cerevisiae Strain 1026) Supplementation on the Closure of Articular Growth Plates in Quarter Horse Foals

To avoid osteoarticular injury and to minimize farm losses in animal use and sales, breaking in young horses is ideally done as soon as growth plates have closed. An experiment was performed to determine whether dietary live yeast could shorten the time for growth plate closure. Twenty-four female Quarter Horse foals, 8 months of age, were allotted to two treatment groups (12 animals each) in a completely randomized experimental design. Horses were fed 0 or 20 g live yeast daily from 8 to 24 months of age. Diets were regular for a stud farm in the area of the study in Argentina. Foals at 8 months of age had a low baseline calcium urinary fractional excretion compatible with a primary calcium-deficient diet for this age in Argentina. Growth plate closure was evaluated by dorsum-palmar radiographs at baseline. A second evaluation was performed when foals were 12 months of age and a third evaluation when foals were 24 months of age. Blood and urine were sampled simultaneously at the same intervals to evaluate bone and mineral metabolism parameters (serum phosphorus, calcium, magnesium; alkaline phosphatase; and hydroxyproline). Calcium, magnesium, and phosphorus urinary fractional excretions were also calculated. Closure scales of distal radius growth plate data were compared using Wilcoxon test and bone markers were compared using Student t-test. Baseline radiological evaluation of growth plates showed that in 84% of foals, the distal metacarpi were either half closed or fully closed at 8 months; therefore, subsequent evaluations were limited to the distal radius. After 4 months of supplementation with live yeast at 12 months of age, a positive but nonsignificant elevation in calcium urinary fractional excretion was observed. At 24 months of age, radiographs showed a nonsignificant but positive effect in the live yeast group, with more than 50% of foals having closed distal radius growth plates. Although bone markers at 24 months of age did not differ (P > .05) between groups, some individual horses showed a positive effect with yeast supplementation.