Abstract
Tall fescue [Schedonorus phoenix (Scop.) Holub] accounts for nearly 16 million hectares of pasture in the Southeastern and Mid-Atlantic U.S. due to its heat, drought, and pest resistance, conferred to the plant by its symbiotic relationship with the endophyte Neotyphodium coenophialum. The endophyte produces ergot alkaloids that have negative effects on the growth and reproduction of animals, resulting in the syndrome known as fescue toxicosis. The objectives of our study were to identify microRNA (miRNA) present in bovine sperm and to evaluate the effects of fescue toxicosis on sperm miRNA expression. Angus bulls were assigned to treatments of either toxic or non-toxic fescue seed diets. Semen was collected and subjected to RNA isolation. Three samples from each treatment group were chosen and pooled for deep sequencing. To compare miRNA expression between treatment groups, a microarray was designed and conducted. For each of the top ten expressed miRNA, target prediction analysis was conducted using TargetScan. Gene ontology enrichment was assessed using the Database for Annotation, Visualization and Integrated Discovery. Sequencing results elucidated the presence of 1,582 unique small RNA present in sperm. Of those sequences, 382 were known Bos taurus miRNA, 22 were known but novel to Bos taurus, and 816 were predicted candidate miRNA that did not map to any currently reported miRNA. Of the sequences chosen for microarray, twenty-two showed significant differential expression between treatment groups. Gene pathways of interest included: regulation of transcription, embryonic development (including blastocyst formation), Wnt and Hedgehog signaling, oocyte meiosis, and kinase and phosphatase activity. MicroRNA present in mature sperm appears to not only be left over from spermatogenic processes, but may actually serve important regulatory roles in fertilization and early developmental processes. Further, our results indicate the possibility that environmental changes may impact the expression of specific miRNA.
Highlights
Tall Fescue [Schedonorus phoenix (Scop.) Holub] is a cool-season perennial grass that is the most widely used cool-season forage in the southeastern United States
Angus bulls (n58) with a scrotal circumference (SC).32 cm were stratified by weight, body condition score, semen quality, and SC and assigned to treatments of either toxic fescue (E+; seed containing ergovaline/ergovalanine at 2.1 mg/kg dry matter) or non-toxic fescue (E2) seed diets [24]
Fescue toxicity in the treatment group was confirmed by monitoring levels of serum prolactin; a decrease was observed in the treatment group but not in the control group [24], a hallmark of toxicity [3]
Summary
Tall Fescue [Schedonorus phoenix (Scop.) Holub] is a cool-season perennial grass that is the most widely used cool-season forage in the southeastern United States. The endophyte produces ergot alkaloid compounds which are beneficial to the plant but have well established negative effects on the growth and reproduction of animals that consume the grass [3, 4]. The few studies in current literature have reported inconsistent effects of grazing infected fescue on sperm motility or morphology. Some studies indicate no effect of fescue toxicosis on sperm function [12, 13], while some report reduced sperm motility [14, 15]. Two studies demonstrated reduced embryo cleavage rates for sperm from bulls either given ergotamine tartrate [16] or subjected to grazing infected fescue [13], even though sperm samples showed no changes in motility or morphology between treatment groups for either study. Some of the current discrepancies in the literature may be due to confounding environmental factors, including heat stress and nutrient content of the diet, which appear to impact the extent of fescue toxicity and are difficult to control consistently [4]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
