Effects of Ergot Alkaloids from Claviceps purpurea on Sperm Characteristics and Prolactin Concentration in Yearling and Mature Angus Bulls

Abstract

Ergot alkaloid contamination of livestock feed is a growing concern in western Canada. There are reports on ergot alkaloid contamination from tall fescue in the United States, but few studies of effects of ergot alkaloid contamination from cereal crops, grains, and grasses. The overall objective of this dissertation was to examine effects of ergot alkaloid-contaminated feed on reproduction in Canadian bulls and to ascertain whether current limits for ergot alkaloids in Canadian national feed regulations are adequate. In the first study, our objective was to determine whether feeding yearling Aberdeen Angus bulls with the highest permissible Canadian limit of ergot alkaloids (~3 mg/kg of daily dry matter intake, DMI; 60µg ergot alkaloid/kg body weight, daily) for 9 weeks would affect sperm characteristics and plasma prolactin concentrations. Plasma prolactin concentrations decreased markedly (mean ± SEM, 16.74 ± 3.70 in Exposure and 33.42 ± 3.08 ng/mL in Post-Exposure periods; P<0.01; n=7) compared to Control (67.54 ± 21.47 and 42.59 ± 15.06 ng/mL; n=7). Ergot treatment did not affect (P0.17) body weight gain, sperm concentration, sperm count/ejaculate, motility or percent live sperm. However, averaged over the exposure and post-exposure durations, scrotal circumference was 2.7% smaller (P=0.02) in the Ergot group. Progressive motility remained unchanged from 59.92 ± 2.31% in Exposure to 59.61 ± 2.59% in Post-Exposure periods, compared to a marked increase in Control (61.42 ± 1.60% to 67.52 ± 1.47%; P=0.02). Straight-line sperm velocity decreased (-3.15 ± 1.53 µm/s) from exposure to post-exposure periods in Ergot group (P=0.04) versus an increase (2.96 ± 2.17 µm/s) in Control. Midpiece defects decreased from Exposure to Post-exposure periods in the Control group, but remained unchanged in the Ergot group (trt*age, P<0.01). Ergot feeding reduced proportion of sperm with medium mitochondrial potential (Ergot: 22.65 ± 0.98%, Control: 24.35 ± 1.05%, P=0.04). In conclusion, Ergot fed at the Canadian permissible limit for 9-wk resulted in a 4-fold decrease in plasma prolactin concentrations. Semen end points were not significantly affected, although there were subtle effects on progressive motility, midpiece defects and mitochondrial membrane potential. Results supported our hypothesis that prolonged low-level ergot will adversely affect plasma prolactin concentrations, and semen end points were partially affected, consistent with similar work on fescue toxicosis. In the second study, our objectives were to determine if feeding mature and yearling Angus bulls ergot alkaloids (from Claviceps purpurea) within the Canadian permissible limit (~3 mg/kg) affect post-thaw sperm quality. In Experiment 1, mature Angus bulls consumed ergot alkaloids (~1 and ~2 mg/kg of daily dry matter intake (DMI); n=8 and n=6 bulls, respectively) for 61 d, with semen collected and cryopreserved bi-weekly. In Experiment 2, yearling Angus bulls (n=7/group) were fed placebo or ergot alkaloids (3.4 mg/kg of DMI) daily for 9 wk, with semen collected and cryopreserved weekly. All frozen semen was assessed 0 and 2 h post-thaw. In Experiment 1, post-thaw total and progressive sperm motilities decreased (P<0.05) from pre-exposure to exposure periods, then rebounded. During exposure, average path velocity (VAP) and straight-line velocity (VSL) decreased (P≤0.01) at 0 h compared to pre-exposure and subsequently rebounded. Live sperm with intact acrosomes at 2 h post-thaw was affected by ergot (P=0.01). Medium mitochondrial membrane potential increased (P≤0.01) during exposure compared to pre-exposure and subsequently decreased. In Experiment 2 on yearling bulls, total and progressive sperm motilities at 0 and 2 h increased (P≤0.01) steadily throughout the study. During post-exposure, curvilinear velocity (VCL), VAP and VSL at 0 h increased (P≤0.01), whereas VSL at 2 h increased (P≤0.01) from pre-exposure to exposure to post-exposure. Live sperm with an intact acrosome increased (P≤0.01) at both 0 and 2 h during post-exposure. Medium mitochondrial membrane potential increased (P≤0.01) from pre-exposure to exposure, followed by a slight decrease in post-exposure. Our hypothesis is partially supported in mature Angus bulls , with only transient effects of ergot on sperm motilities and velocities after cryopreservation. Post-thaw sperm characteristics in yearling bulls underwent expected age-related improvements, with any effects of ergot alkaloids potentially masked by sexual maturation. Overall, in both studies, results partially supported our hypotheses that ergot has no detectable long-term adverse effect on fresh or post-thaw sperm characteristics in yearling or mature bulls. This work will provide important evidence for producers working with ergot-contaminated grain or ergot-exposed cattle.