Managing Reproduction on Toxic Fescue
JOPLIN, Mo. (Sept. 1, 2011) There are no silver bullets when it comes to managing the challenges associated with cattle grazing endophyte-infected tall fescue. Challenges include reduced feed intake and performance, reduced fertility rates, increased respiration and body temperature and necrosis of the extremities due to constricted blood flow.
Research indicates fescue toxicosis affects either the growing oocyte (egg) or early embryo while it's still in the oviduct, Neal Schrick said. Late-pregnancy losses are no higher for cows grazing infected fescue compared to those on the noninfected variety.
But there are ways to manage the challenges and reap the advantages provided by the widely used forage. That’s what Neal Schrick, an animal science professor at the University of Tennessee (UT) told participants at the Applied Reproductive Strategies in Beef Cattle (ARSBC) conference in Joplin Aug. 31-Sept. 1.
For instance, recent UT research suggests that breeding cows (spring-calving) in a narrower window of time can help mitigate the negative reproductive impacts. Though not conclusive, the research is helping explain why.
On the cow side, Schrick explained, the research indicates fescue toxicosis affects either the growing oocyte (egg) or early embryo while it’s still in the oviduct. That’s why late-pregnancy losses are no higher for cows grazing infected fescue compared to those on the non-infected variety. In the UT studies, Schrick said, “If cows were pregnant at 35 days, they stayed pregnant.”
As for bulls, UT research indicates, “the fertilization ability or potential (ability to cleave) is reduced in semen from bulls grazing endophyte-infected fescue. Reduced cleavage rate is associated with the reduced penetration rate of spermatozoa into the oocyte.
As well, Schrick explained, semen collected from bulls grazing infected pastures have reduced post-thaw motility.
With the effect of fescue toxicosis on both bulls and females, Schrick said one recommendation is to remove cows from the toxic pastures for 30 days prior to breeding season and for 30 days afterward. He understands that may not be practical.
“More practical would be to have your cows calving early if spring calving and get them exposed to the bull before the hot summer months occur,” Schrick said. He added that work at UT indicates June 10-12 is the latest breeding date in that state to avoid the most significant reproductive losses associated with tall fescue. Later into the summer, Schrick explained, cows get bred, but the calving season gets spread out.
“When I look at fescue, I have to think about it and heat stress as one and the same,” Schrick said. “That’s why fall breeding on tall fescue works better.”
As well, Schrick emphasized adding clover to pastures and feeding supplemental grain are proven management techniques that help dilute the effect of fescue toxicosis.
“Remember, clover is your friend,” Schrick said, stressing the recommendation that clover represent 25%-30% of the forage in an infected fescue pasture.
For anyone wanting to know how to gauge the proportion of clover in a pasture, Schrick related advice he heard someone give: “Take 10 steps across the pasture. If you step on clover three times, you’re at 30%.”
There are still plenty of unanswered questions about how fescue toxicosis affects cattle performance and reproduction. For instance, Schrick explained, “A lot of producers plant MaxQ (an endophyte-free fescue variety) for their breeding pastures and then move them to endophyte-infected pastures. Will that be a problem? We don’t know.”
Schrick spoke during Thursday's ARSBC session focused on the nutritional influences on reproduction. Visit the Newsroom at www.appliedreprostrategies.com to view the PowerPoint slides and proceedings paper submitted by Schrick to accompany his presentation. Audio of the presentation will be available soon.
Comprehensive coverage of the symposium is available online at www.appliedreprostrategies.com. Compiled by Angus Productions Inc. (API), the site is made possible through sponsorship by the Beef Reproductive Task Force, SEK Genetics, and liveauctions.tv. Coverage includes summaries of the speaker presentations, PowerPoints, proceedings and audio.
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