Effects of feeding 60% dried corn distillers grains or the equivalent sulfur as CaSO4 on DNA integrity and gene expression in yearling Angus bull sperm

Authors: KASSETAS, CIERRAH - North Dakota State University; Geary, Thomas; Zezeski, Abby; CATON, JOEL - North Dakota State University; KIRSCH, JAMES - North Dakota State University; DORSAM, SHERI - North Dakota State University; DA SILVA DINIZ, WELLISON - North Dakota State University; MCCARTHY, KACIE - University Of Nebraska; Crouse, Matthew; DAHLEN, CARL - North Dakota State University; SEDIVEC, KEVIN - North Dakota State University; NEVILLE, BRYAN - North Dakota State University

Submitted to: Ruminants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/2023
Publication Date: 10/1/2023
Citation: Kassetas, C.J., Geary, T.W., Zezeski, A.L., Caton, J.S., Kirsch, J.D., Dorsam, S.T., Da Silva Diniz, W.J., McCarthy, K.L., Crouse, M.S., Dahlen, C.R., Sedivec, K.K., Neville, B.W. 2023. Effects of feeding 60% dried corn distillers grains or the equivalent sulfur as CaSO4 on DNA integrity and gene expression in yearling Angus bull sperm. Ruminants. 3:286-298. https://doi.org/10.3390/ruminants3040026.
DOI: https://doi.org/10.3390/ruminants3040026

Interpretive Summary: Dried distillers grain with solubles (DDGS) is a byproduct of the ethanol industry that is also a cheap source of both energy and protein for livestock. It is also high in sulfur, which could be problematic if used as the sole source of feed. The first goal of this study was to learn if feeding a DDGS to bulls would affect fertility. Because of the high sulfur content in DDGS, one group of bulls was fed a supplement without DDGS but high in sulfur. A third group of bulls was fed a normal diet without DDGS and lower in sulfur. Bulls were individually fed for 112 days. Semen was obtained from bulls and evaluated for several fertility measures. Traditional measures of fertility revealed no major effects of the DDGS or high sulfur diets. A second goal was to evaluate diet effects on gene expression in sperm and novel measures of fertility. Thirty-six half-brother Angus bulls were used in this study. Bulls fed the high sulfur diet had sperm with greater energy potential than other bulls. Bulls fed the normal diet had sperm expected to live longer in the female reproductive tract and were considered more fertile. Few genes were affected by bull diets. Gene expression of protamine 1 (PRM1) was greater in sperm from DDGS bulls. Increased PRM1 generally improves DNA integrity, but no differences in sperm DNA integrity were detected. We conclude that diets containing 60% DDGS, or high sulfur, have minimal effects on bull fertility.

Technical Abstract: The objectives of this study were to evaluate the effects of feeding 60% dried corn distillers grains plus solubles (DDGS) or the equivalent sulfur as CaSO4 on acrosome/cell membrane integrity, mitochondrial energy potential, oxidation status, DNA integrity, and zinc signatures in frozen/extended bull semen and gene expression in sperm. Thirty-six half-sibling Angus bulls [256 ' 8.5 d; initial BW = 320 ' 2.7 kg] were assigned to one of three treatments: 1) corn-based diet containing 60% concentrate as corn (CON; S = 0.18% DM; n = 12); 2) diet containing 60% DDGS as a replacement for corn (60DDGS; S = 0.55% DM; n = 12); 3) CON diet + equivalent sulfur of 60DDGS added as CaSO4 (SULF; S = 0.54% DM; n = 12). Bulls were individually fed in Calan gates for 112 days and targeted to gain 1.6 kg/d. Semen was collected via electroejaculation at d 112. A portion of each semen sample was extended and frozen for flow cytometry assays while another portion was used to isolate and sequence gene transcripts. The Guava easyCyte 5HT Flow Cytometer was used to analyze acrosome/cell membrane integrity, mitochondrial energy potential, oxidation status, DNA integrity, and zinc signatures. Sperm-specific gene expression was assessed with RNA sequencing. All flow cytometry data were analyzed using PROC MIXED in SAS for effects of treatment. Pairwise comparisons based on edgeR were used to identify differentially expressed genes. No differences (P > 0.15) were observed among treatments for viability, acrosome integrity, oxidation potential, and DNA integrity assays. Percentage of polarized mitochondria tended to be greater (P = 0.08) for SULF compared with CON and 60DDGS. Additionally, no differences (P = 0.11) were observed among treatments for zinc signatures 2 through 4. However, zinc signature 1in 60DDGS and SULF was reduced (P = 0.03) compared to CON. This suggests that sperm from bulls in the SULF and 60DDGS treatments may be in advanced stages of sperm capacitation in comparison to CON, potentially limiting the sperm lifespan and ability to bind the sperm oviductal reservoir. Overall, few differentially expressed genes were observed in the current experiment. Protamine 1 was upregulated (P < 0.01; FDR = 0.10) in 60DDGS compared to CON. Furthermore, these results indicate that sulfur from DDGS may not be influencing sperm DNA integrity or gene expression in yearling Angus bulls.