Effect of supplemental trace minerals on standard and novel measure of bull fertility

Authors: Geary, Thomas; Waterman, Richard; VAN EMON, MEGAN - Montana State University; RATZBURG, COLE - University Of Wyoming; LAKE, SCOTT - University Of Wyoming; EIK, BRAD - Montana State University; ARMSTRONG, DOUG - Montana State University; Zezeski, Abby; HELDT, JEFF - Micronutrients Usa Llc

Submitted to: Theriogenology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/2021
Publication Date: 7/16/2021
Citation: Geary, T.W., Waterman, R.C., Van Emon, M.L., Ratzburg, C.R., Lake, S., Eik, B.A., Armstrong, D.R., Zezeski, A.L., Heldt, J.S. 2021. Effect of supplemental trace minerals on standard and novel measure of bull fertility. Theriogenology. 172:307-314. https://doi.org/10.1016/j.theriogenology.2021.07.006.
DOI: https://doi.org/10.1016/j.theriogenology.2021.07.006

Interpretive Summary: Two studies were conducted to evaluate fertility in mature and yearling bulls fed specific minerals. In the first study, mature bulls were fed different sources of mineral for 71 days and fertility evaluated. Bulls were fed supplement with no mineral (CON) or supplement with sulfate (SULF) or chloride (CHLR) forms of copper, zinc, and manganese. In the second study, yearling bulls were fed supplement with no mineral (CON) or supplement with zinc (ZN), copper (CU), or both zinc and copper (ZNCU). Fertility was measured every 28 days. Liver samples were collected at the beginning and end of each study to measure mineral storage. In mature bulls, final liver Zn levels were predictive of sperm concentration. Liver zinc levels were also related to sperm damage. Yearling bulls fed copper (CU) or zinc plus copper (ZNCU) stored more copper in their liver than CON or ZN bulls. Only bulls fed the ZNCU supplement stored more zinc in their liver. In yearling bulls, all fertility measures improved with age. Surprisingly, only minor differences in fertility were detected between bulls fed different mineral treatments. Bulls fed mineral produced fewer abnormal sperm than CON bulls. Bulls fed mineral produced sperm with greater survival after 3 hours of incubation than CON bulls. Bulls fed no mineral (CON) also produced sperm that were less able to survive stress than bulls that were fed mineral. We conclude that bulls can maintain mineral levels for long periods of time even when feed contains low levels of mineral. Bulls exposed to breeding or fed diets that bind up these minerals might respond differently.

Technical Abstract: Two studies were conducted to evaluate the effects of trace mineral supplementation on traditional and novel measures of bull fertility. In experiment 1, 37 mature bulls received one of three dietary supplements daily for 71 d: 1) Supplement without Cu, Zn, and Mn (CON); 2) Supplement with Cu, Zn, and Mn sulfate (SULF); and 3) Supplement with basic Cu chloride, and Zn and Mn hydroxychloride (CHLR). In experiment 2, 128 Angus or Angus-Hereford calves were maintained on a growing diet for 75 d (year 1) or 119 d (year 2) in Calan gate equipped pens without mineral supplementation. Bulls (n = 32 head/treatment) received one of four trace mineral supplements daily for 84 d: 1) Zn with no Cu (ZN), 2) Cu with no Zn (CU), 3) Cu and Zn (ZNCU), or 4) no Cu or Zn (CON). Fertility measures included a breeding soundness examination (BSE) and novel fertility measures conducted using flow cytometry. In mature bulls, final liver Zn concentration was positively correlated (P = 0.02) with sperm concentration (r = 0.31) and tended (P = 0.06) to be negatively correlated with acrosome damage (r = -0.39). Peripubertal bulls receiving ZNCU had greater ADG than CU bulls (P = 0.05). Each BSE and novel fertility component improved from d 0 to 84 in peripubertal bulls and were not affected (P > 0.10) by mineral supplementation. Bulls that received no supplement (CON) had greater (P < 0.01) percentage of sperm with distal midpiece reflex and Dag defect in their ejaculates. Sperm viability after 30 min of incubation were not affected by trace mineral supplementation, but after 3 h incubation, sperm viability tended to differ (P = 0.06) between treatments and tended to be less for CON bulls compared to ZNCU bulls. Among contrast comparisons, trace mineral supplemented bulls had greater (P < 0.05) percentage of viable sperm at 3 h post collection and reactive oxygen resistant sperm than CON bulls. Addition of Zn to trace mineral containing Cu (ZNCU) improved (P < 0.05) percentage of sperm in the ejaculate with high mitochondrial energy potential and viable sperm with intact acrosome membrane. In summary, it appears the homeostasis mechanisms for bull trace mineral maintenance are extremely efficient and mineral supplementation of mature and peripubertal bulls did not have major improvements in any laboratory or chute-side measures of bull fertility, however bulls exposed to breeding or in environments with diet antagonists might respond differently.