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Northwest Iowa Dairy Outlooks

A local discussion of current science and issues concerning dairying in northwest iowa

Dr. Larry A. Redmon, Texas AgriLife Extension Service Forage Specialist, reports that recently, 15 head of Corriente roping calves died as a result of prussic acid poisoning in Bastrop cattle in a clean field of Tifton 85 bermudagrass.  While this has never been reported before, results of analyses of rumen contents and the fresh forage confirmed death was due to prussic acid poisoning.

A little background is in order.  Tifton 85 bermudagrass was released from the USDA-ARS station at Tifton, GA in 1992 by Dr. Glenn Burton, the same gentleman who gave us Coastal bermudagrass in 1943.  One of the parents of Tifton 85, Tifton 68, is a stargrass.  Stargrass is in the same genus as bermudagrass (Cynodon) but is a different species (nlemfuensis versus dactylon) than bermudagrass.  Stargrass has a pretty high potential for prussic acid formation, depending on variety, but even with that being said, University of Florida researchers at the Ona, FL station have grazed stargrass since 1972 without a prussic acid incident.

The pasture where the cattle died had been severely drought stressed from last year’s unprecedented drought, and had Prowl H2O applied during the dormant season, a small amount of fertilizer applied in mid to late April, received approximately 5” of precipitation within the previous 30 days, and was at a hay harvest stage of growth.  Thus, the pasture did not fit the typical young flush of growth following a drought-ending rain or young growth following a frost we typically associate with prussic acid formation.

The cattle were stressed, hungry, and thirsty when they had finished roping for the evening; this is obviously not the ideal condition for cattle to be in when turned into a pasture that had not been grazed this season.  However, this is not the answer to the problem.  There is, although it appears to be an isolated event, prussic acid potential, and therefore potential for cattle death when grazing Tifton 85 bermudagrass.

Producers who currently have Tifton 85 pastures should be advised, not paniced about their Tifton 85 bermudagrass.  Here are some important points to consider:

1)      Never turn hungry, stressed animals into a new pasture; allow them to fill on hay or in a familiar pasture first.

2)      When turning cattle into a field of Tifton 85, pay close attention for the first hour or so to ensure cattle will not be in distress.  If in doubt, obtain a fresh forage sample from the upper 1/3 of the canopy, place in a ziplock bag on ice, and get to the vet diagnostic lab immediately for analysis.

3)      Make sure any Tifton 85 forage harvested for hay is properly field-cured before baling.

4)      If producers currently have cattle on Tifton 85 pastures, it is unlikely they will experience problems.

5)      Have producers report any unusual deaths to you (to obtain forage samples) and the local vet.

6)      Tifton 85 bermudagrass still has the highest level of drought tolerance of all bermudagrass varieties and the highest level of animal performance of all warm-season perennial grasses.

Again, this situation has never been reported and the incident in Bastrop County is an isolated event.


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