Role of Fescue in Reproduction
Fescue, energy and protein influence fertility.
by Kasey Brown, associate editor
STAUNTON, Va. (Oct. 15, 2013) — Most cattlemen know that energy and protein are imperative to reproductive success, but for cattlemen in the east, fescue can also affect fertility, said Mark McCann, professor and beef cattle extension specialist with Virginia Tech. He spoke to more than 170 attendees of the 2013 Applied Reproductive Strategies in Beef Cattle (ARSBC) symposium in Staunton, Va., Oct. 15-16.
Mark McCann, a beef extension specialist for Virginia Tech, shared four strategies to minimize the negative effects of toxic fescue on reproduction in the beef herd: dilution with other feedstuffs, pasture renovation, managing seedheads, and switching to fall calving.
“For those of us east of the Mississippi [River], most of our green grazed forages meet protein requirements,” he said.
About 90% of the tall fescue in the southeastern United States is infected with wild-type “toxic” fungus, and this fescue is consumed by cattle, horses and sheep, McCann noted. This fungus, or endophyte, is symbiotic with the grass in that it makes the grass drought-tolerant and insect-resistant. However, it produces ergot alkaloids that are toxic to livestock, he explained. These toxins are most prevalent when the plant is actively growing and dissipate with time after the plant stops growing.
What happens to toxin levels after harvesting the forage? McCann reported data that showed endophyte levels in green-chopped forage at 1,200 parts per billion (ppb). When the fescue was ensiled, toxin levels dropped to 900 ppb. When it was cut for hay, levels dropped to 300 ppb, with most of that drop coming within the first week after harvest. Ammoniating the hay reduced toxin levels even further, to 250 ppb.
McCann encouraged producers to test pastures for endophyte, as many pastures that are assumed to be too toxic aren’t always at dangerous levels.
To suppress toxic fescue seedheads, McCann compared several options. Reported success with grazing, including rotational grazing, is anecdotal, he said. Clipping pastures is effective, but expensive. The herbicide Chaparral applied at a rate of 2 ounces per acre has been demonstrated to suppress stem and seedhead formation. That increases the average quality of the forage, but kills clover that is often used to dilute fescue cow diets.
McCann said signs of fescue toxicity include zero serum prolactin, high rectal temperatures, heat stress behavior, lower average daily gain, lower gain per acre, and lower dry-matter intake. Available forage tends to be higher because cows eat less of what’s there.
There is an option for “friendly fescue,” which doesn’t produce the toxins harmful to cattle, said McCann, mentioning MaxQ® as an example. It is naturally occurring, has agronomic benefits and “combines the best of both worlds.” This is a more expensive option, though.
Fescue toxins affect bulls by decreasing performance and elevating body temperatures. They have little impact on scrotal circumference or sperm motility or morphology, but they reduce the fertilization ability of the sperm. Affected cows show higher body temperatures, lower prolactin levels, lower cow and calf performance, lower pregnancy rate, lower embryo quality, and lower embryo development. The effects for both bulls and cows occur before Day 7 of embryo development.
Switching to fall calving has helped manage around fescue toxicity, reducing its effect on reproduction, he reported.
McCann concluded by reiterating four mitigation strategies:
- dilute fescue stands with clover, other forage species or other feed;
- renovate pastures with “friendly-fescue”;
- manage seedheads through grazing management or chemicals; and
- consider a fall calving season.
McCann spoke during Wednesday's ARSBC session focused on special issues in beef cattle reproduction. For more information, visit the Newsroom at www.appliedreprostrategies.com to listen to his presentation and to view his PowerPoint slides.
Comprehensive coverage of the symposium is available online at www.appliedreprostrategies.com. Compiled by the Angus Journal editorial team, the site is made possible through sponsorship by the Beef Reproductive Task Force.
Editor's Note: This article was written under contract or by staff of the Angus Journal. To request reprint permission and guidelines, contact Shauna Rose Hermel, editor, at 816-383-5270.