71 Lameness responses to a single exercise bout following dietary supplementation of Saccharomyces cerevisiae fermentation product in young horses

Yearling Quarter Horses (mean ± SEM; 561 ± 3 d; 373.3 ± 5 kg BW; 13 fillies, 14 colts) were used in a randomized complete block to test the hypothesis that dietary supplementation of a postbiotic Saccharomyces cerevisiae fermentation product (SCFP) mitigates lameness following a single exercise bout in young horses. For the 76-d trial, yearlings were fed a basal diet of 1% BW/d (as-fed) grain-based horse feed formulated without added microbials (SafeChoice® Original, Nutrena) twice daily plus ad libitum Coastal bermudagrass (Cynodon datylon) hay, and water. Horses were grouped by age, sex, and BW and randomly assigned to 1) concentrate only (CON; n = 10), 2) concentrate top dressed with 46 mg/kg SCFP (TRT 1; n = 8), or 3) concentrate top dressed with 92 mg/kg SCFP (TRT 2; n = 9). Objective lameness assessments were obtained by a wireless Inertial Sensor System (ISS) followed by a subjective evaluation performed by a licensed veterinarian. All horses underwent a baseline lameness assessment on d 0, followed by 2 lameness assessments on d 76 (pre-exercise, and post-exercise). Objective lameness evaluations were performed at the trot for 2 30 m, back-and-forth passes, wearing the wireless ISS lameness analysis system and evaluated in triplicate per assessment. For the subjective lameness analysis, horses were additionallytrotted in a circle in both directions within a 16 × 14 m area and evaluated by an individual licensed veterinarian using the American Association of Equine Practitioners (AAEP) lameness scale. Data were analyzed using PROC GLM in SAS v9.4 with diet and time included as fixed effects. When analyzing AAEP lameness evaluations, no differences were detected for dietary treatment or diet × time interactions related to primary (P = 0.55; P = 0.98), secondary (P = 0.43; P = 0.78), or tertiary (P = 0.77; P = 0.77) limbs. Additionally, no dietary treatment effects or diet × time interactions were detected using the wireless ISS for front Q score (P = 0.19; P = 0.92) or hind pushoff Q score (P = 0.53; P = 0.27). Furthermore, there was no effect of dietary treatment on hind impact Q score (P = 0.68). However, there tended to be a diet × time interaction (P = 0.06) whereby horses on TRT 2 tended to have a lower hind impact Q score. Additionally, post-exercise front Q scores increased over time (P ≤ 0.01) compared with both baseline and pre-exercise values regardless of dietary treatment. These results indicate the intensity of exercise may not have been sufficient to lead to dietary differences related to gait asymmetry.