Effects of injectable trace mineral supplementation on yearling bull growth, carcass characteristics, testicular development and semen quality attributes

Abstract Text: The study objective was to evaluate effects of injectable trace mineral supplementation on growth, carcass characteristics, testicular development and semen quality in yearling Angus bulls. Bulls (446 kg ± 35, SD) were blocked by age into 4 pens of 15, and randomly assigned to receive Multimin 90 (MM) or a saline injection (CON; n = 30 per treatment) at 1 ml/68 kg BW and fed a common finishing diet for 73d. Breeding soundness exams (BSE) and scrotal circumference measurements were conducted on d 53 on all bulls. Liver and blood mineral concentrations (n =14/treatment) were determined on d 1 and 53, and semen mineral concentrations were also determined on d 53. Bulls were harvested on d 74 and testicles were assessed for testicular density and histology, and carcass data collected after a 48-h chill. Data were analyzed using MIXED or GLIMMIX procedures of SAS with the fixed effect of treatment and bull as the experimental unit.  Days of age (BSE, testicular data) and initial mineral concentrations (plasma, liver) were used as covariates. No differences due to treatment were observed in ADG, carcass characteristics, testicular density or histology (P ≥ 0.27). Results from BSE indicate no differences in scrotal circumference, testicular tone, morphology, or pass/fail percentages (P ≥ 0.30) between treatments; however, overall motility (P = 0.07) tended to be lesser in MM-bulls. Based on reference ranges, d 1 liver mineral concentrations were considered adequate in all bulls. Day 53 liver and plasma mineral concentrations were similar between MM and CON treatments (P ≥ 0.15). Treatment did not affect whole semen mineral concentrations (P ≥ 0.18), or Se, Zn, and Mn concentrations (P ≥ 0.48) of seminal plasma. However, seminal plasma Cu concentrations were greater in MM bulls (P = 0.04).  Spermatozoa concentrations of Se and Zn (P ≥ 0.27) did not differ due to treatment; however, spermatozoa Cu tended (P = 0.07) to be lesser and spermatozoa Mn concentrations were decreased (P = 0.03) in MM-bulls.  Interestingly, spermatozoa Mn concentrations were negatively correlated with morphology (r = -0.41, P = 0.04). These data suggest supplementing bulls adequate in mineral status with MM does not affect growth, carcass characteristics or semen attributes.  However, semen mineral concentrations may be related to semen quality and more work is needed to clarify the importance of mineral distribution in semen fractions on semen quality.

Keywords: bulls, semen quality, trace minerals