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.  Forage specialists and researchers here and the vet diagnostic lab at first denied the possibility of this.  Even the researchers and breeders at USDA-ARS – Tifton, GA, doubted the findings, but after multiple site visits, multiple forage analyses, and DNA analysis of plants from several fields from several environments across Texas, we can come to only one conclusion – the death of the cattle was indeed 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.
Some private individuals are beginning to issue their own notices at sale barns.  This is not the type of announcement our producers need as all this does is alarm people and not inform them, so we plan to issue a news release in the near future explaining essentially what I have described in this message.  BUT, I wanted you to know before the news release was issued.  In fact, you will receive the news release first before we go to Ag Communications for public distribution.
What we wish to do is to advise, but not alarm those who currently have Tifton 85 pastures.  Here are some important points for producers 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…so far.  I just wanted each of you to know about the situation so you would not be blindsided if someone in the county was to ask the question “What is this I hear about Tifton 85 bermudagrass…”
Source: Dr. Larry Redmon, Texas State Forage Extension Specialist