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The long and short of fescue toxicity

TL;DR:

  • Fescue toxicity has symptoms of restricted blood flow and reduced performance, like feed intake.
  • Pregnant Charolais and Hereford grazed toxic fescue and had different levels of symptoms.
  • Charolais appear to be more resilient to the effects of toxic fescue.

What you need to know: Fescue is a grass that is exceptionally drought tolerant but can also harbor toxicity during the summer months. Fescue toxicity, caused by endophyte-infections of the grass, has symptoms of restricted blood flow, retention of a thick hair coat, and reduced performance metrics like feed intake.

To improve the utilization of this grass, researchers have been searching for ways to blunt the effects of toxic fescue consumption. Pregnant Charolais and Hereford cows were put on either toxic on non-toxic fescue pastures for over 150 days to see if the two breeds had different levels of symptoms from the toxic fescue.

As expected, toxic fescue pastures impacted the productivity and health of all cows consuming the forage. However, Hereford cattle had greater breaths per minute and body temperature and lower mineral status and hair loss. Charolais appear to be more resilient to the effects of toxic fescue.

A primary finding was that hair retention of cows eating toxic fescue was also associated with higher body temperatures. Additionally, Herefords have greater hair retention than Charolais in this data, which was made worse by toxic fescue pastures—combined, suggesting that Herefords had more significant symptoms due to their natural hair retention being greater than Charolais.

The important asterisk*:

  1. The animals in this research only had access to water every other week, as they were on a pasture rotation that only allowed access to a pond intermittently. However, herds on toxic and non-toxic pastures both had limited water - suggesting the comparison is fair.  
  2. Many of the measurements, like body weight, were only collected on two occasions; day 0 (the start of the trial) and day 156 (end of the trial). More measures across the trial length would be better, but that would be hard with the design.  

Industry Application: When a ranch has toxic fescue, it could be beneficial for commercial producers to use cattle breeds that are less impacted, like Charlois and potentially other breeds with more ability to shed hair.

Read more about it: Identification of Breed Differences in Known and New Fescue Toxicosis Associated Phenotypes in Charolais-and Hereford-Sired Crossbred Beef Cows