Nutritional Influences of Endophyte-Infected Tall Fescue on Reproduction
by Barb Baylor Anderson for Angus Productions Inc.
NASHVILLE, TENN. (Aug. 6, 2010) — Getting beef cows pregnant in the Southeast can be an issue for some producers where endophyte-infected tall fescue is present. Neal Schrick, University of Tennessee animal scientist, told participants at the Applied Reproductive Strategies in Beef Cattle (ARSBC) Conference in Nashville, Tenn., August 6, 2010, that the issue is being explored, but with few specific conclusions.
Neal Schrick, UT animal scientist, recommended producers remove cows from endophyte-infected tall fescue pastures for 30 days before and after breeding.
"These fescue issues may be management issues. We do not know if cattle have been selected over time to be tolerant to fescue, or whether there is uterine adaptation or whether adaptation can fade if bulls are sent to test stations and come back to a herd," Schrick said. "Have animals been selected for adaptation here? I'll leave that question for the genetic researchers."
Schrick said endophyte-infected tall fescue can cause poor performance in cattle, including reduced intake, higher respiration rates and excessive salivation. Toxicosis can further cause decreased calving and pregnancy rates to the tune of more than $600 million annually in the U.S.
"We see problems when weed spraying kills clover, we stockpile fescue and when we bring in cattle from non-fescue-infected areas," he said. "Less time grazing means lower fertility. But fescue is a good grass, and it needs to be grazed. It fits in with the needs of the cows here."
Schrick and others have studied possible causes on both the female and male sides of the issue. Potential female issues include how fescue toxicosis may affect either the growing egg or early embryo while still in the oviduct on the female side.
"When you add in the effects of tall fescue on the sperm, we can understand why fertility is reduced," he said. "Throw in elevated temperatures during the summer months with little or no clover and we could see a 'reproductive wreck.'"
Schrick recommended producers remove cows from fescue for 30 days before and after breeding. He has seen no effect on pregnancy rates. A more practical solution, he added, may be to have cows calve early and get them exposed to the bull before hot summer months.
"We intend to perform more studies to determine if we can manage females differently around the time of breeding to improve pregnancy rates when grazing infected tall fescue," he said.
On the male side, Schrick and colleagues have studied grazing bulls and evaluated the semen. In the work, scrotal circumference and semen motility and morphology were similar between treated and control bulls, but fertilization potential was reduced in treated bulls compared to controls. In addition, testicular core temperatures were reduced in treated bulls even though rectal temperatures were elevated. Additional work will be conducted on males as well.
"Future studies include determining effects of the fescue on reproduction parameters of mature bulls and sperm defects associated with toxicosis and reduced fertilization ability," he said. "Another study would include evaluation of tall fescue effects on bulls that have been removed from infected pastures for a period of time, then re-introduced during the breeding period."
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