Effect of supplemental tracemineral source on bull semen quality

This study evaluated the effect of tracemineral supplementation on bull semen quality, as measured by computer-assisted sperm analysis. Angus and Gelbvieh × Angus bulls assigned to inorganic (n = 9) and organic (n = 10) trace-mineral treatments were maintained in drylot pens and fed mixed grass hay. Three times weekly bulls were individually fed rations containing either inorganic or a mixture of inorganic and organic Zn, Cu, Co, and Mn trace mineral for 123 d (mid-May to early September). Starting on d 60, semen was collected by electroejaculation weekly for a 9-wk period (mid-July until early September) and evaluated by computer-assisted sperm analysis for motility parameters within 5 min of collection. Data were analyzed by treatment, week, and their interaction using SAS PROC Mixed for repeated measures. Bulls supplemented with organic trace minerals had a greater (P = 0.02) percentage of motile sperm than those supplemented with inorganic trace minerals (65.5 vs. 56.1%, respectively). Likewise, percentage of progressive sperm was greater (P = 0.01) for bulls receiving organic (47.0%) versus only inorganic (38.4%) trace mineral. Sperm with rapid motility (path velocity > 50 μm/s) was also greater (P = 0.03) for bulls supplemented with organic compared with bulls receiving inorganic trace mineral (62.3 vs. 52.8%, respectively). Sperm motility is the single most important semen quality parameter influencing bull fertility. Results suggest organic trace-mineral supplementation may improve bull semen quality. Additional studies are needed to determine whether this improvement in semen quality translates into improved pregnancy rates.