Effects of copper and zinc supplementation on standard and novel measures of fertility in peripubertal beef bulls [Abstract]

Authors: Geary, Thomas; Waterman, Richard; VAN EMON, MEGAN - Montana State University; Zezeski, Abby; HELDT, JEFF - Nutreco; SPEARS, JERRY - Nutreco

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/6/2018
Publication Date: 5/27/2018
Citation: Geary, T.W., Waterman, R.C., Van Emon, M., Zezeski, A.L., Heldt, J., Spears, J. 2018. Effects of copper and zinc supplementation on standard and novel measures of fertility in peripubertal beef bulls [Abstract]. Meeting Abstract. 4.

Interpretive Summary:

Technical Abstract: Application: National Research Council (NRC) recommendations of dietary copper and zinc are beneficial for yearling bull gain, but may exceed that needed for fertility. Introduction: Considerable variation exists in the percentage of beef bulls that reach puberty and pass a breeding soundness exam (BSE) by 14 months of age. Understanding the variables that enhance puberty and improve fertility of bulls would allow management of bulls for optimal fertility. The value of mineral supplementation in diets of peripubertal bulls has been inconsistent and has relied on standard BSE measures. Effects of mineral supplements on novel measures of sperm fertility using flow cytometry have not been evaluated previously. Our objective was to determine the effects of copper and zinc supplementation on novel measures of sperm fertility in the peripubertal bull measured with flow cytometry. Material and methods Predominantly Angus bull calves (n = 80) weaned at approximately 178 days of age and maintained on a growing diet without mineral supplementation until 307 days of age were blocked by sire and stratified by body weight to 1 of 20 pens equipped with Calan gate individual feed bunks. Bulls were randomly assigned within pen to one of four trace mineral treatments: 1) zinc with no copper (ZN, 299 mg/d; n = 20), 2) copper with no zinc (CU, 131 mg/d; n = 20), 3) ZN + CU (ZNCU; n = 20), and 4) no copper or zinc (CON; n = 20) as supplements provided daily to a corn silage/alfalfa hay/corn/wheat growing diet. Mineral treatments were supplied as basic copper chloride and zinc hydroxychloride (Micronutrients USA LLC, Indianapolis, IN, USA) formulated so that the total mixed ration would meet or exceed NRC requirements for copper and zinc with the assumption that only 50% of the mineral in the basal diet was bio-available. Diets were fed 84 d with liver biopsies collected on d 0 and 85, and weight, scrotal circumference (SC), semen, and blood collected every 28 d. Two ejaculates were collected from each bull on d 0, 28, 56, and 84 for evaluation of sperm concentration, motility, and morphology as part of a standard BSE, as well as energy potential, acrosome integrity, viability, antioxidant capacity, and DNA integrity using flow cytometry. Liver biopsies (d 0 & 85) and semen samples (d 0 & 84) were evaluated for trace mineral concentration using inductively coupled plasma mass spectrometry. Bulls were classified as pubertal (50 x 106 spermatozoa in the ejaculate with > 10% progressive motility) and assigned a BSE score of Pass (prog. motility = 30% + SC = 30 cm + normal morph. = 70%), Pass-High (Pass with prog. motility = 60%), or Fail. Linear data were analysed using mixed model with d 0 measures as covariates, whereas categorical data were analysed using Chi Square. Pearson correlation coefficients were analysed using a multivariate analysis. Results Four bulls were removed from the study for reasons unrelated to treatments so that each treatment was applied to 19 bulls. On d 0, liver copper (30.6 ± 4.0 ppm) was low, but liver copper and zinc (105.0 ± 2.1 ppm) were similar for all bulls. Bulls that received CON and ZN supplements were still low (64.0 ± 6.0 ppm) in liver copper on d 85, whereas CU and ZNCU supplemented bulls were adequate (237. 8 ± 6.0 ppm) in liver copper and greater (P<0.001) than CON and ZN bulls. Supplement type did not affect (P = 0.65) liver zinc concentration (118.4 ± 2.1 ppm) on d 85. There was an effect (P=0.02) of treatment on ADG of bulls, with ZNCU bulls (1.53 ± 0.04 kg) gaining faster (P<0.05) than other bulls (1.42 ± 0.04 kg). Fewer (P < 0.01) bulls assigned the CU treatment were pubertal on d 0, but by d 28, there were no differences (P=0.55) in pubertal status across treatments. A greater (P=0.04) percentage of CON bulls passed the d 0 BSE than bulls in other treatments, but by d 28, there